Evo Midterm 2 Study Guide
Lecture 11: (Know virus examples and TSE examples)
What is life?: life has 2 characteristics, organized and replicates itself.
Virus Structure: Highly organized, easily recognizable, mutate, evolve and replicate themselves. Derived from components of living cells, protein coat.
Capsid/Protein Coat: Surrounds virus, contains nucleotides in strands, either RNA OR DNA (never both), linear, circular, single or double stranded, no plasma membrane, cytosol, or organelles.
Viral Hereditary Material: Single or double stranded, needs host in order to replicate. Virions: Individual viral particles, highly organized.
Helical and Icosahedral Shapes: Shape of most viruses, helical = plant virus (TMV) icosahedral has 20 equilateral triangular facets, maximizes internal capacity without increasing size, holds more in less space.
Binal: Both icosahedral and helical elements, complex viruses, specifically infects bacteria. Bacteriophage: 4X the size of hemoglobin, infects by bacteria, bacterial virus, infects and reproduces inside of it.
The basics of viral reproduction: Parasitic infection, tricks hose cell into replication, thus copies of viral genome + capsid proteins, another set of instructions tricks host cell. Infected cell usually become destroyed, outer protein coat is stripped, and cells own processes are disrupted. Why do some scientists argue that viruses are not alive? Why do other scientists disagree? TSE and some examples: Transmissible Spongiform Encephalopathies, fatal diseases of the brain, neurons die and the brain becomes spongey. Scrapie (Sheep), Bovine Spongiform encephalopathy (mad cow disease), Chronic wasting disease (deer), Creutzfeld Jakob Disease (humans), slow spreading viruses. We also discuss several other topics like What does federalism refers to?
How are prions different than viruses?: Prions are passed by proteins only, misfolded versions of normal proteins, no DNA or RNA, no genetic material.
Why were prions originally called slow viruses?: Due to time of infection and when the disease was actually detected.
How is the traditional (5 or 6 kingdom) view of the tree of life based?: Tips are no equal, tree of life is rather misleading.
The new tree: Highlights major split between bacteria and archae, each group is monophyletic. LUCA: Last universal common ancestor, traits shared by all life forms evolved here. Traits shared by all life forms: Plasma membrane bound cells, ribosomes, semiconservative DNA replication, similar genetic codes for proteins, transcription, translation, and metabolic pathways.
Key Traits common to Bacteria and Archaea: Don't forget about the age old question of what are manhattan project is?
Defining traits of Eukaryotes: Multicellular, compartmentalized, and mostly sexual. How is the new Eukaryotic Tree different from older views?:Don't forget about the age old question of what are the 5 Senses?
Lecture 12: (Know Thermotoga Maritima, Bacillus anthracis, Botulisms, Mycoplasmas, Tuberculosis, Actinomyces, Syphilis, Lyme Disease, Escherichia coli, Salmonella, Plague, and Methanopyrus.
Why is “prokaryotes” in quotes?: Because we only know 110%, don’t know much about them, same reason we only spend one day on 2/3’s of the tree of life.
Differentiate the “prokaryotes” from the eurkayotes:
a. Unicellular: Typically, unicellular, colonies or filaments, of free internal structure, no membrane bounded organelles.
b. Internal Structure: No membrane bounded organelles.
c. Chromosomes: Singular circular DNA chromosome.
d. Cell division: Binary fission, simple, fast, split in half.
e. Gene transfer: Lateral transfer movement of chunks from one to another. f. Cell Wall: Ubiquitous, peptidoglycan.
g. Flagella: Simple, single fiber, rigid and spins.
h. Size: Typically small
Nucleoid: Region where we would find circular chromosome.
Web of life vs. Tree of life: Really important genes move horizontally, tree of life is otherwise. Peptidoglycan, Pseudomurein: Polymers of sugars and amino acids.
Gram + and Gram – Bacteria, Archaea?: Gram + cells retain dye and turn blue. Gram – don’t retain, become red because gram + stain binds to the polymer component found in bacteria, peptidoglycan bc thick layer.
PreDNA bacterial classification:
a. Shape (bacilli, cocci, spirilla): Cocci=circular, bacilli=lines, spirilla=spirals b. Metabolism (anerobes [facultative, obligate, aerotolerant], aerobes, photoautotrophs, photoherterotrophs, chemoautotrophs, chemoheterotrophs): c. Other classification topics: We also discuss several other topics like What are the functions of mitotic cell division?
Hadobacteria and Hyperthermic bacteria: Both are extreme heat lovers, function best at a high temperature. Hadobacteria=Deinoccoccus radiodurans can consume nuclear waste. Firmicutes: Diverse, gram +, thick peptidoglycan, some produce endosperms which are heat resistant dormant structures, can survives harsh conditions, bacillus anthrosis returning to dormancy after many years.
Actinobacteria: Gram +, filamentous, appears strand like, tuberculosis attack and kill other bacteria, actinomyces break down organic soil.
Cyanobacteria: Critical photoautotrophs, blue green bacteria, gram , live in long filamentous strands.
Spirochetes: Gram , heterotrophs, axial filaments, common pathogens run from end to end, overlap in middle, rotate around and causes motion.
Chlamydias: Gram , very small, obligate parasites, cannot live independently, complex life cycles, one enters host and other develops inside.
Proteobacteria: Largest and most diverse group, photoheterotrophs, variety of metabolism, all 4 metabolic styles, Escherichia coli, salmonella, vibrio cholerae are all gram .We also discuss several other topics like What is the movement formed by anti-nationalistic movement?
Metagenomics or environmental genomics: Where you take a sample and sequence it and all the species found in it are identified and counted even if they are not observed. Helps us learn about archaens.
Lokiarchaeota: Archaen, lok is castle, sister taxa to eukaryotes, many genes related to cell membranes (eukaryotes)
Crenarcheota: Loving extreme environments, hold, cold, acidic, flourish at many pH. Maintain an internal pH between 5.57, marine archaen, fixation of carbon.
Extremophiles (Thermophilic, Cryophilic, Halophilic, etc.):
Methanogens: Methane producing bacteria, animal intestines, methane contributing to the greenhouse effect.
Lecture 13: (Know Gymnopodium, Plasmodium Falciparum, Paramecium, Giant Kelp, White Rust, and Giardia intestinalis.
Eukaryote Traits: Multicellularity (allows for flexibility about environments they encounter), Sexual Reproduction (leads to increased genetic diversity, increases speed of adaptation), Compartmentalization (organelles carry out independent functions, requires several stages), flexible cell surface, cytoskeleton, nuclear envelope, digestive vacuoles, and endosymbiosis. How does compartmentalization lead to internal structure?: Cell wall lost, allows membrane to fold in, create more surface area without increasing size, organelles form. Why is the loss of the cell wall critical to eukaryotic development?: It allows for a more fluid plasma membrane, allows for endocytosis and increase in surface area without increasing size. Formation of Organelles: Result of membrane infolding. If you want to learn more check out what is the difference between Graded potential and Action Potential?
Endosymbiosis leading to mitochondria and chloroplasts: Ancestral eukaryotic cell engulfed aerobic bacterium, mitochondria formed through endosymbiosis with proteobaterium and cyanobacteria to lead to the development of chloroplasts.
How are the protists profoundly paraphyletic?: Very diverse, grouped by what they are not. Variation in Protist traits
a. Locomotion: Movement via flagella, cilia or pseupodia (sticky protrusions) b. Cell Surfaces: Many have some form of extracellular material on plasma membrane. c. Nutrition: Auto and heterotrophic, no photoheterotrophs in this group, some as
photosynthetic due to primary endosymbiosis and others secondary endosymbiosis (engulfed another eukaryote).
d. Reproduction: Sexual (ciliates) and asexual in amoebas.
The development of multicellularity: Eukaryotic cells began living in close association, then became colonies, individuals in colony take on different roles, colony begins to function as an individual. Protists show us this development.
a. Alveolates: Monophyletic group of primarily single celled organisms that all have alveoli.
1. Dinoflagellates: Unicellular marine photosynthetic luminous organisms that provide nutrients to species like coral, 2 flagella in a platelike armor.
2. Apicomplexa: Spore forming parasites with apical complexes that allow them to invade the host, plasmodium=malaria.
3. Ciliates: Unicellular, large, move using cilia, heterotrophic, Paramecium. b. Stramenopiles: Characterized by fine hairs extending from their flagella. 1. Diatoms: Photosynthetic, small, unicellular, excrete protective silica cells, reproduce using both asexual and sexual reproduction, only males have flagella. 2. Brown algaes: Large, multicellular organisms, secondary endosymbiosis w red algae, giant kelp.
3. Oomycetes (water molds and downy mildews): nonmoving, decomposers and use external digestion.
c. Rhizarians (ex: Foramaninferans): unicellular and aquatic w/rigid, thin pseudopodia, fossilize easily because inorganic material.
d. Excavates: Some eukaryotes that do not have mitochondria.
1. Diplomonads and Parabasalids: Do not have mitochondria, often causes disease, derived trait.
2. Euglenids: Can be heterotrophs or photoautotrophs, have mitochondria, unique flagella, lost ability to be sexual, exclusively binary fission,
e. Amoebozoans: Contain amoebas and slime molds, lobe shaped pseudopodia for locomotion and eating.
1. Loboseans: Unicellular amoebas that live independently as individuals. 2. Plasmodial and cellular slime molds: Can exists asexually as long as there is enough food, release spores to make new slime molds.
f. ChoanoflagellatesWithin Opisthikonts with animals and fungus: Ancestral to animals, resemble modern sponges.
Lecture 14: (Know Giant sequoia, Sequoiadendron giganteum, Coast Redwood, Sequoia sempervirens, Chlamydomonas, Volvox, Red algaes (species that makes Nori), and Chara). Major ways plants differ from protists: Multicellularity.
Challenges of land living: Drying out, structural support, reproduction, air presents aquatic organisms with complexities, support without water, dependent on water for gametes. Adaptations to land dwelling: Embryophytic (they have some structure to protect the developing embryo from drying out), cuticle (waxy substance secreted that prevents the plant itself from drying out, traps water inside), stomata (little holes that open to let air in and close to keep plants from drying out), pigmentation (blocks out UV), fungal relationship (helps them better absorb nutrients, free floating) trachead cells (allow for water and nutrient transport throughout plant body), and seeds (allow for protection of embryo).
Diplontic life cycle: diploid stages that are multicellular, any haploid stage is unicellular, only diploid stages can undergo mitosis.
Haplodiplontic life cycle:
1. Sporangia: Where meiosis occurs, specialized structures, diploid.
2. Spore Mother Cells: undergo mitosis and produce haploid spores.
3. Spores: Divide by mitosis and grow into a mature haploid gametophyte.
4. Archegonium: produces eggs.
5. Antheridium: produces sperm.
6. Zygote: Fertilized cell, single diploid cells, haploid>diploid generations. 7. Embryo:
Sporophyte: Diploid, produces haploid spores, leads to alternation of generations. Gametophyte: Mature haploid via mitosis.
How do the events of meiosis and syngamy (fertilization) shape the haplodiplontic life cycle?:
Dominant life stages:
Describe different ways to define “plants”.
Rhodophyta (Red algaes): 7000 species, wide array of sizes, multiple pigments, accessory photosynthetic pigments.
Chloroplasts formation: Result of primary endosymbiosis, single event that gave rise to red and green algae.
Primary and secondary endosymbiosis: Land plants=primary, brown algaes= secondary. Chlorophyll types:
Chlorophytes: green plants, most green algaes, similar cell form to land plants, volvox. Stoneworts: green algae, sister to land plants, filamentous cell forms, many other homologous traits with land plants, mitosis style cell structures.
Nonvascular Plants (Bryophytes):
What does it mean to be nonvascular?: Lacking tracheid cells that transfer water or nutrients, cells are inneficient.
Traits of bryophytes: nonmonophyletic, no tracheid cells, small, embryophytic, gametophyte dominant, sporophyte dependent on gametophyte, water required for sexual reproduction. Moss Life cycle:
Tracheid cells (xylem and phloem): system of transport, water and minerals up xylem, sugar and nutrients down phloem.
Benefits of tracheids:
Seedless vascular plants (Tracheophytes): all have vascular system, not monophyletic, embryophytic, sporophyte dominant, freeliving gametophyte, can get very large. Lycophytes: Most primitive tracheophytes, generally small.
Microphylls and megaphylls:
Sori: Clusters of sporangia.
Fern Life Cycle:
Lecture 15: (Know Ginkgo biloba, Welwitschia, and Ephedra (Mormon tea). Parts of a Seed:
1. Megaspore: large haploid spore formed by some plants that develops into a female gametophyte. Produced by female cones that develop into female gametophytes In plants, a haploid spore that produces a female haploid egg and endosperm. 2. Megasporangium: Surrounds megaspore.
3. Integument: Organ system that forms a protective covering on the outside, protection. 4. Micropyle: Opening that allows for entry of pollen grain.
Three ways seeds are adaptive:
b. Dispersal: can disperse far from parent plant
c. Dormancy: internal food source allows this, delay between development and dispersal, or dispersal and sprouting, allows seed to choose when to open, can wait for a time of high resources and good environmental conditions, increases survival rate after sprouting
Homospory vs Heterospory: In a homosporous life cycle, sporophyte produces single type of spore comes form 2N sporangium, get 1N spore, becomes mature gametophytes. In a heterosporous life cycle, mature sporophytes produce two types of sporangia, female and male sporangia, usually on different parts of the plant, pollen baring cones. Contain microspore mother cells, destined to undergo meiosis and divide to produce mother spores, one of two types of spores will develop and undergo mitoses and develop into pollen grains, seed baring cones. Microspore Mother cell, microspores, pollen, sperm: male gametophyte, Multicellular, dispersed to get to female gametophytes, Entire male gametophyte moves, Individual cells are the male gametes, still unicellular haploid cells, sperm are derived from mitosis within gametophyte and fertilize egg in female gametophytes.
Ovules, megaspore mother cell, megaspore, female gametophyte: seed baring cones, contain ovals on scale of cone, 2 per scale, developed into seeds after fertilization, seeds housed in cone and dispersed when whole cone falls off seed before fertilization contains mother cells enclosed in protective tissue and is dependent on the sporophyte for nutrition. (mother cells)
megaspore produce 4 haploid daughter cells, one survives, female gametophyte, hundreds of cells, reduced all the way to 8 cells in angiosperm. Seed barring plants show further reduction in gametophytic phase, in gymnosperms have hundred so cells, angiosperms have 8 cells. Naked seeds: gymnosperms, divide into 4 groups
Pollen Tube: Linked to pollen grain, entry of pollen.
Why aren’t seed plants dependent on water?: Seed pollen grain developing pollen tube allows plants to live in bigger variety of environments and forms.
Cycads: ancient, age of dinosaurs, can be large, slow growing, resemble palm trees, bear cones. Motile sperm swim down pollen tube, largest sperm in any living organism. Ginkgos: once widely distributed, northern hemisphere, once thought to be extinct, one extant species and dioecious (separate male and female individuals).
Gnetophytes: Share tracheid cells, have vessel cells like angiosperms that are homoplasious, convergence. 3 genera, Gretum, Welwitschia, Ephedra. Welwitschia has only 2 leaves, dioecious, Ephedra has medicinal uses.
Conifers: Most common, tallest organisms in the world is redwood.
Traits of angiosperms (flowers and fruit): Functions as an attractment for dispersers, limits competition. Flower structures all evolved from leaves.
Types of fruits: apple (bottom part=sepal), tomato (true berry w/fused carpels), legume (ovaries spell up + sugar), peach (called a drupe, seed inside pit), blackberries (many ovaries), pineapple (compound fruit, many flowers on a single stem).
Egg, Synergids,Antipodals, Polar nuclei: egg is held in place by synergids, antipodals give structure and keep egg cell in place, polar nuclei fuses with polar body and forms triploid cells. Pollen tube, tube cell, generative cell: Pollen tube houses 2 important cells, tube cell divides and causes pollen tube to grow, leads way down tube to ovary. Generative cell = haploid. Double fertilization, 2N Zygote, 3N endosperm: when sperm enter gametophyte, one fertilizes egg and forms 2N zygote, other comes up to where two polar nuclei fuses with polar body forms triploid cells, primary endosperm nucleus rapidly divides and forms nutritive tissue that surrounds seeds, the two unions are called double fertilizations. It only happens in angiosperms, after this seed develops and germinates to form new sporophyte.
How is the angiosperm life cycle different then the gymnosperm life cycle?: Reduced # in female gametophyte, speed of pollen tube growth, double fertilization, triploid endosperm, and fruit.
What do we think made angiosperms so successful?: Vessel cells, more efficient growth, rapid maturation, pollinators (more expansion) and fruits.
Lecture 16: (Know Archefructus, Amborella trichopoda, Water lily, Star anise, Magnolids, Nutmeg, Rose, Pea, Daffodil, Orchid, and trap flowers).
What is the “abominable mystery”?:
The nine clades of angiosperms (focus on the seven in your book)
a. Archaefructus: Shrubs, herbaceous, pre flowers, no petals or sepals, male+female reproductive parts.
b. Amborella: New Caledonia, small tree, shrub, hermaphroditic but only one sex fully develops, functionally dioecious and very small.
c. Nymphaeales (water lilies): 80 species of aquatic plants, stomata on one side of leaves (opening for air and water), no vessel cells, extended leaf and flower stems. d. Astrobaileyas: small new group, 100 species of woody plants in tropic and temperate regions, star anise is a dried fruit that looks star shaped, spice as well. Evergreen plant that doesn’t lose its leaves.
e. Chloranthaceae: Several dozen species of woody plants.
f. Ceratophyllum: Aquarium plants. 6 species, just under the fresh water surface, protection, high oxygen producing.
g. Magnolids: 9000 species, economically important for life. Trimerous flowers, in 3s. Broad leaves and branching veins.
h. Eudicots: 521,000 species, most successful angiosperms. 45 merous flowers, parts in 4 or 5. Also broad leaves and branching veins.
i. Monocots: 70,000 species, all basic grains are monocots. Thin leaves with parallel veins, long and trimerous.
Definition of pollination syndrome: Set of traits flower has that adapted to a specific pollinator. Pollination vs Fertilization: Pollination=mating, while fertilization is when cells come together.
Abiotic vs biotic (generally and with regard to pollination): abiotic is nonliving, while biotic is living, insects were the earliest we think, increases floral specialization in plants. Specific pollination syndromes:
a. Water (abiotic): ancestral form, aquatic floating pollen, not water soluble but still germinates, must have pollen that can float and germinate, plants must be close together. b. Wind (abiotic): successful form, one of the first for land plants, small green odorless flowers, large clusters on pendant tassels so they can wave in the wind, reduced petals, clusters of anthers, plants should be close together.
c. Beetle (biotic): fossils of beetles carrying pollen, angiosperm as well, usually large green flowers, heavily scented like spicy, fruity, or decaying organic material. Flattened because beetles need to be able to walk around, accessible pollen.
d. Bees (biotic): shorttongued (and flies) can’t get into tubular flowers nor can they hover. Need open and exposed flowers, no nectar, small overall size. Longtonged bees (and butterflies) can access deep nectar wells, yellow or purple blue coloring, spots, stripes or lines (nectar guides) indicate where nectar is.
e. Fly (biotic):
f. Butterflies (biotic): showy, open flat and thin tubular flowers that are pink and lavender in color, frequently with a landing area. Flowers are almost always scented. More nectar offered then pollen, lots of amino acids insides tubes or spurs, more opportunity.
g. Moths (biotic): Hover extremely well, rapid wing be at flowers, no landing area necessary. Nocturnal or orespuscular. White or pale, strongly scented flowers with long nectar spurs with lots of nectar, high metabolic needs for moths.
h. Hummingbird (biotic): large deep tubular flowers, nectar low in amino acids, red or orange and not scented, birds can see red very well.
i. Bats (biotic): largest flowers, very white and showy, open at night with strong odor. Bell shaped and hang down, lots of nectar for extended time. Rely on smell and visual cues. Spatial memory, echolocation on pools on liquid.
Coevolution: two species that evolve in concert, in response to each other. Nectar guide: spots, stripes or lines that indicate where nectar is.
UV Spectrum and pollination:
What do flowers “get” out of these coevolutionary relationships?: They get pollen or nectar, the give pollen, and they make sure pollinators don’t take rewards without getting/giving pollen. The example Aristolochia (trap flowers): Magnolid Pipe flowers, long trumpet like opening, flies pollinate up tube deep into base, reverse oriented hairs, can easily move through but cannot fly back out, once stigma receives pollen triggers maturation of anthers, release pollen on the fly, and after the anthers dehiss, hairs will shrivel up and fly can escape.
How do fungi fit onto the eukaryotic tree?: They are more closely related to animals than plants, own unique monophyletic clade, branch very close to animals, choanoflagellates and animals, common ancestor protest.
“Unifying Fungal traits:
Cell types: Unicellular free leaving yeast and multicellular, most fungus are filamentous.
a. Hyphae: Long chains of cell like structures joined end to end.
b. Septa: acts as a barrier.
c. Septate fungi vs. Coenocytic fungi: with septa = septate fungi, lacking = coenocyte d. Mycelium: forms complex structure. Clusters of hyphae.
Fungal Digestion/Absorptive Heterotrophy: External digestion.
How does the fungal body plan reflect nutrient intake in fungus?: Digestive reproductive structures with clusters of hyphae.
Cell Walls with chitin:
Fungal Nuclei and dikaryons: Dikaryons form from the fusion of two haploid mating strains, protects from mutations. Nuclei are haploid in cell and exist independently, they do not fuse. Dikaryon formation: when two haploid mating strains form.
Asexual and sexual reproduction can occur in one life cycle:
Spores are reproductive structures:
Plasmogamy: cell fusion, cells fuse but nuclei do not. Results in spores
Karyogamy: nuclear marriage, fusion of two haploid nuclei to form a diploid nucleus. Importance of Sexual stages for identification: Critical for defining species also phylogenetic placement of fungus.
Microsporidia: sounds like a virus, small, obligate intracellular parasites, infect with polar tube, contents inserted into host and replicated, replicated by host cell, and lack a true mitochondria. Mitosome: has double membrane, looks like mitochondria. Derived from mitochondria, indicates they were lost. After this the Microsporidia branched off.
Chytridiomycetes: likely paraphyletic. Aquatic, unicellular life stages. Flagella present, coenocytic. Can be found in the stomachs of cattle.
Amphibian Decline: Chytrids may be cause b/c they kill amphibians that they reside on by producing harmful spores (deadlier at colder temps). Example= batrachochytrium dendrobatidis (kill amphibians).
Zygomycetes: saprobic or parasitic. Terrestrial, no septa, coenocytic. Sexual reproduction is rare, but still produce zygotes. Find Gametangia, Zygosporangium, and Zygospore in them only. Gametangia: are mycorhizzal, coenocytic and don't form mycelia (remain single strands). Can't live without host, all terrestrial.
Zygosporangium and Zygospore: Zygosporangium is where gametes mate, leads to many unfused nuclei, once they fuse you get a multinucleit. A Zygospore is a multinucleit, all nuclei inside are 2N and can remain dormant, eventually portions will undergo meiosis and produce spores.
Glomeromycetes: only 150 species and made invasion of land by plants possible. Coenocytic, don't form mycelia.
Mycorrhizae: form mutualistic relationships with plants. Hyphae grow in roots of trees and plants. Allows for beneficial nutrients exchange for both. They can't live without their hosts b/c get their sugars from the host's photosynthesis. We've never observed sexual reproduction by them, monophyletic.
Ascomycetes: 75% of species, septate, dikaryon forming, bear spores in cups.
Basidiomycetes: most mushrooms, largest species, Basidocarps. Septate, dikaryon forming. Three ways to feed:
a. Mutalists: exchange nutrients with other species, live in conjunction with other species. b. Saprophytes/Saprobes: digest/eat dead materials "decomposers"
c. Parasites: eat living tissue on living organisms. Examples= athlete's foot, ring worm. Why are fungal diseases hard to treat?: b/c they typically attack other eukaryotes, so hard to treat the fungus without "treating" the host.
Lecture 18: (Know sea jellies, box jellies, anemones, corals, tapeworms, flukes, clitellates (earthworms and leeches) polychaetes (ex:tube worms).
Traits that unify animals: Heterotrophic, multicellular, motility, sexual reproduction, characteristic embryonic development, shared hox genes drive development, specialized tissues (except sponges).
a. Radial: Leads to body designs around a central point, generally circular, very early forming,
b. Bilateral: Right and left halves are symmetrical, top and bottom, dorsal and ventral, anterior and posterior.
Dorsal, ventral, anterior, posterior: Improves animal complexity.
Cephalization: Where sensory organs are concentrated, anterior end, evolution of brain area, synapomorhpy, ancestral.
Diploblastic Development: diploblastic animals have two layers 1. ectoderm 2 endoderm. Triploblastic Development: have an intermediate tissue layer (the mesoderm) which led to increasingly complex body plan.
Endoderm, ectoderm, mesoderm: Endoderm is the inner digestive layer, ectoderm is the outer body covering, nervous system, and the mesoderm is the muscle and nervous tissue. Benefits of Variable tissues:
Protostome vs. Deuterostome: The protostome is an indentation that becomes the mouth and the deuterostome is when anuses develop before the mouth.
Acoelomates, pseudocoelomates, coelomates: Acoelomates have no space between tissue layer, typically move by cilia. Pseudocoelomates have cavity that's fluid filled (gives them rigidness) and fluid can also function as a hydrostatic skeleton and a circulatory system. Coelomates have cavity inside mesoderm, organs are lined in muscle (gives them a lot of control). Segmentation and Locomotion: Segmentation allows for redundancy of function and specialization and locomotion is more efficient when segments can move independently. How has the DNA based tree changed from the old morphological tree?: says differentiating based on coeloms isn't correct b/c both coeloms and pseudocoeloms are homoplasious. But we do still look at different types of symmetry and protostome vs. deutorostome. Lophotrochozans: grow by adding mass to already existing bodies.
Ecdysozoans: molt/shed hard exoskeleton in order to grow (NOT SNAKES) Sponges: monophyletic, used to be considered the most basal animals, range in size, larvae are free swimming.
Ctenophores (comb jellies): Branched off before any other animal group, evolved indepdently for a very long time.
Homoplasious traits found in ctenophores: Radial symmetry, disploblastic, complete gut, nerve nets.
a. Choanocytes: highly specialized cells, exactly what a choanoflagellate looks like. Long, flagellated cells that line the sponges that collect food particles as they pass by. b. Water pores: pump water, brings food and oxygen in, lets waste out. Cnidarians: Radial, diploblasts, marine predator, true tissues and nerve nests, have not yet developed organs, incomplete gut, gastrovascular cavity.
Polyps: Diploblast. Usually anchored and colonial, but there are a few free swimming ones. Examples= Anemones, Corals.
Medusae: Diploblastic. Free swimming, usually umbrella shaped with tentacles surrounding mouth. Examples= Sea jellies, Box jellies.
Cnidarian digestion: In medusae, takes place in its gut like cavity (gastrovascular cavity). This is a form of external digestion since cavity is technically outside of the body. Allows it to eat organisms larger than itself.
Bilaterians: Defined by bilateral symmetry. Have protosomes and deutersomes. But one group does have radial symmetry.
Bryozoans and Entoprocts: live in colonies, protective membranes, sexual reproduction. Flatworms: one gut opening, true head, cannot eat, digest and waste at the same time, lacks organs, must be near surface, hermaphroditic, act simultaneously as both sexes. Rotifers: Tiny pseudocleomates, complete gut, complex organs.
Rotifer corona: circle of cilia that sweeps food into mouth.
Ribbon worms: proboscis and vary greatly in length. Complete digestive tract, asceolomate. Use cilia like flatworms but can also use muscle contractions to move.
Proboscis: Feeding appendages.
Annelids: coelomate, segmented worms. 2 classes 1=earthworms and leeches 2= polychaeles (beautiful with unusual forms/colors). can have 2 or more pairs of eyes/tentacles.
Lecture 19: (Know Slugs, Snails, Nudibranchs, Clams, Mussels, Oysters, Scallops, Octopus, Squid, Nautilus, Horseshoe Crab, Caenorhabditis elegans or C. elegans, Ticks, Spiders, Centipedes, Millipedes, Shrimp, Lobster, Crab, Pill Bug, Grasshopper, Dragonfly.) What did the common ancestor to mollusks look like?: unsegmented, marine warm. Parts and various roles of the generalized mollusk body plan:
a. Visceral mass: Holds the organs, digestive, etc.
b. Foot (muscular): tough structure, locomotion and attachment, and food capture. c. Mantle: Thickened sheet of skin, dorsal part, covers respiratory organs and secreting a shell.
Cephalization in the mollusks: some have very pronounced heads, some have no heads at all (so varying levels of Cephalization).
Radula: Specialized mouth part, many rows of teeth, some drill like.
Mollusk reproduction: Cross fertilization.
Polyplacophora (Chitons): small overlapping bodies with 8 dorsal plates, foot, herbivorous radula, shallow waters, intertidal zones, mainly external fertilization but some internal. Gastropods: Snails, Nudibranchs, and Slugs. Some creep along and others free swim. Tentacles are common (used for eyes and chemo/mechano sensing). Most are marine. Bivalves: Marine and freshwater. Ligament holds shell closed and most filter feed. Have in current (brings stuff in) and excurrent (water and gametes out) syphons. Sedentary adults, foot for anchoring or digging. Free swimming larvae, external fertilization. Examples= Mussels, Oysters, Scallops, Clams.
Cephalopods: exclusively marine, active predators. They have arms and tentacles, and are coloring changing and use jet propulsion. Are highly intelligent and have a highly developed nervous system/eyes. Examples= Octopus, Squid, Nautilus.
What makes an ecdysozoan?: They grow by molting (have a hard outer covering called their exoskeleton). They're monophyletic.
Nematodes (Roundworms): Species rich, pseudocoelomates. Typically parasitic and have separate sexes. Hydrostatic skeleton and can also be active predators. They have complete guts and are covered by a protective cuticle (which they shed 4 times). Have lateral Muscles and are Eutely. Examples= Hookworms, Pinworms,
Eutely: adult has a fixed number of cells, makes it nice for us to study them and then compare it to other organisms.
Model Organisms: define the way we study a certain topic or field. Example= Nematodes since they are Eutely.
Horsehair worms: ecdysozoan. Larvae and adults are very different and they range widely in length. Almost all are freshwater and the adults have no mouth and a nonfunctioning gut. We think they may only feed as larvae.
Water bears: Extremely small and live on sand/water film on plants, can remain dormant for a very long time and ecdysozoan.
Onychophorans: closely related to arthropods, terrestrial (only one to be solely terrestrial), segmented and unjointed, thin cuticle with chitin, major constituent of insect exoskeleton, internal fertilization and internal egg development.
What did the common ancestor of the arthropods probably look like?: Species richness (number of species) of arthropods: 2/3rds of all species on Earth are arthropods (and most of those are insects).
Trilobites: had jointed appendages and heavy exoskeletons. They were fossilized which lets us see this. (also had heads).
Jointed appendages and body segments in arthropods (head, thorax, abdomen): Body segmented into head, thorax, abdomen. Body plans are dominated by jointed appendages which is good b/c they can extend and retract.
Exoskeletons in arthropods: Have them, made from excreted Chitin and protein. It's what the muscles are attached to. They then grow a new skeleton under the old one. The Exoskeleton has to get thicker as the muscles get bigger, that's why they stay relatively small. Molting in arthropods: old skeleton pops open, arthropod puffs itself up to make the new exoskeleton harder, but he's very vulnerable at this point so he goes into hiding.
Limitations placed on organisms with exoskeletons:
Differentiations between arthropod groups:
a. Arachnids (Chelicerae, eight legs, etc.): Have chelicerae as mouth parts, four pairs of legs. Pinchers highly specialized. Examples= ticks, spiders, scorpions.
b. Myriapods (Repeating segments, leg pairs, etc.): Segmented bodies, mouthparts are mandibles, head, one pair on antennae + repeated segments.
c. Crustaceans (Two antennae, threepart bodies, etc.): Head, thorax, abdomen, only anthropods with 2 pairs of antennae, mandibles, marine forms.
d. Insects: (Six legs, antennae, threepart bodies, etc.): Mandibles, head, thorax, abdomen. 6 legs, hexapods, one pair of antennae.
Lecture 20: (Know Sea lilies, feather stars, sea urchins, sand dollars, sea cucombers, sea stars, brittle stars, acorn worms, tunicates, and lancelets.
What makes a deuterostome?: Relatively few out there, only 3 major groups named b/c development is marked by mouth, reverse of protostomes, internal skeletons, some have internal segmentation, monophyletic. Fossils have the traits found in modern echinoderms and chordates. Ex: Homalozoans.
Ancestral deuterostomes: homalozoans:
Echinoderms: First deuterstome, closely related to us, tight relationship is example of how basic morphology = unclear evolution.
Pentardial symmetry: radial symmetry, 5 axes of symmetry or sometimes multiples of 5, we know that they are not closely related to the radial groups.
Echinoderm Larvae: they have bilateral larvae.
Water vasculature system: water filled canals leading to the tube feet. Used for feeding, gas exchange, locomotion.
Madreporite and tube feet: sea water enters it, goes into ring canal, then into the canals in all arms, then to tube feet. Tube feet also used for attachment.
Oral Surface: headless b/c bilateral. It's underneath, what they crawl on. Aboral Surface: opposite of oral surface.
Asexual and sexual reproduction in echinoderms: asexual: form of regeneration, many can regenerate lost parts. Most are sexual though: there are males and females but they look very similar. Gametes released into water, external fertilization.
Extinct echinoderms: 20 extinct classes.
The three groups of echinoderms:
a. Crinoids: Sea lilies, feather stars have flexible arms attach to surface, can walk and swim, unusually shaped, many arms, flexible stalk.
b. Echinozoans: Spine animals, have no arms, sea urchins (spines attached to the internal skeleton with ball and socket joint, move to converge and deliver painful sometimes static sting), sand dollars (lines of symmetry are clear), sea cucumbers (use to be separate group, similar genetics, look bilateral but simply elongated, pentaradial, clustered tube feet, crawling).
c. Asterozoans: Star animals, made up of sea stars (most important predators in marine habitats) and brittle stars (similar, yet much thinner arms, jointed hard plates yet flexible, no suckers, arms used for feeding, largest group, nocturnal, circadium rhythm.
Hermichordates: Are the sister taxa to echinoderms, have a 3part body plan. Example=Acorn Worm (up to 2 m long).
Chordate traits: (first 3 embryological development)
a. Dorsal Hollow Nerve Cord: develops into Brain and spinal nerve cord, runs just below dorsal surface.
b. Notochord: place just above gut and just below dorsal hollow nerve cord. Plays a role in nervous system development or becomes part of the vertebral column.
c. Pharyngeal gill slits: connects pharynx to external environment, allows us to swallow. But pouches never open on terrestrial vertebrates. It's an ancestral trait that was lost in echinoderms but present in chordates.
d. Postanal tail: extends away from the body.
Chordate Segmentation: all chordates as segmented.
Nonvertebral chordate groups (Lancelets and Tunicates):
a. Lancelets: Small, when ready to reproduce, gonads swell and burst open, releasing gametes into the water.
b. Tunicates: Size varies, form colonies, asexual budding (traits clear in larval form, shows relation).
Lecture 21: (Know Sea horses/leafy sea dragons, tunas, eels, manta rays, Coelancanths and lungifha, Ichthyostega, frogs and toads, salamanders, mud puppies, caecilians, Eryops megacephalus).
Vertebrate traits: all have heads, endoskeletons supported by vertebrae, internal organs suspended in a coelom, and a welldeveloped circulatory system with heart. a. Head: anterior skull (bone or cartilage) with large brain. 3 well developed sensory organs, ears, eyes and or nose/mouth.
b. Endoskeleton supported by vertebrae: protects dorsal nerve cord (which allows brain to direct movements). It's made of cartilage or bone which is advantageous over chitin in that it grows with you and allows us to be big.
c. Internal Organs: Suspended in coelom, liver, gut, kidney, endocrine system. d. Circulatory system: Well developed, muscular heart powers it, extremely important. Where to put the hagfish?:The outgroup to vertebrates, have weak circulatory system, 3 accessory hearts, partial skull, brain lacking 2 major regions, neither jaws nor stomach, recent evidence related to lampreys, sister species.
Hagfish and Lampreys: Cylostomes: May have been first vertebrates, and Hagfish lost the vertebral traits.
Vertebrate groups: Fish, amphibians, mammals, reptiles, birds.
Fish Diversity (only full aquatic group): Very diverse and numerous, fully aquatic vertebrates allow for the invasion of land by amphibians. Yellow finned tuna 8ft, 500 pounds. Five traits of all fish:
a. Jaws: Feeding efficiency, allow them to catch and eat large pray.
b. Paired appendages (pectoral or pelvic pair): Used to stabilize position and repulsion, repel them, evolve to be jointed (gives us our appendages).
c. Internal gills: allow for oxygen extraction from water.
d. Single loop blood circulation: blood is pumped from heart to gills (where it gets oxygen), then to the rest of the body, then back to the heart. Our circulatory system is double looped.
e. Amino acid deficiencies: 3 amino acids cannot synthesize, must be consumed in food. Passed on to rest of invertebrate.
Agnathans, extinct placoderms, and modern Gnathostomes show the evolution and importance of jaws: Agnathans had no jaws and after they split off tree the placoderms arose and jaws replaced with ancestors to sharks and bony fish. Much improved jaws. Sharks and Rays: Sharks have lightweight strong skeletons, first to evolve teeth, chewing allows to aid in digestion and increased nutrient release/uptake. 20000 teeth in a lifetime, more prevalent early in evolution. 3rd mass extinction sharks went through diversification. Rays are relatively small but are capable of getting large.
The importance of teeth: chewing allows to aid in digestion and increased nutrient release/uptake.
Cartilage vs. Bone: Cartilage makes organisms fast and agile and bone is heavy but strong and gives power of movement. Has allowed the transition to land to occur.
Swim bladders: Provides buoyancy (originally gas filled sac) used to counter heavy bony skeleton. Can increase or decrease air in it, allows fish to control position in water and remain buoyant.
Rayfinned fish vs. Lobefinned fish (esp.locomotion): Rayfinned fish have parallel bony rays that stiffen their fins and their internal muscles control their fin movements. They move their fins in concert. There are only 8 species of lobefinned fish today. They have muscular lobes and central core of bones in fleshy lobe to forms joints. They only have the ray bones in the tips of their fins. Examples= Coelacanths and Lungfish.
Challenges of land invasion: moving heavy bodies, replacing gills, increasing oxygen intake and delivery to larger muscles for walking, preventing drying out of eggs, and preventing the body from drying out.
Tetrapods: fourlimbed vertebrates.
Amphibians: Double life, still highly dependent on water.
Traits shared by modern amphibians:
a. Legs: Walking.
b. Lungs: Less surface area for oxygen than in mammals or reptiles, so they supplement oxygen intake.
c. Cutaneous respiration: Absorb oxygen through the skin and release carbon dioxide. d. Pulmonary Veins: Specialized to return oxygenated blood to the heart to pump to rest of the body.
e. Partially divided hearts: what gets pumped out to the rest of the body isn't fully oxygenated b/c little hole that mixes oxygenated and nonoxygenated.
Major amphibian groups: Frogs, Salamanders, and Caecilians.
a. Frogs and Toads: Amphibians without tails, frogs have smooth moist skin, long legs, close to water. Toads have dry bumpy skin, short legs, dryer environments. Dependent on water for reproduction and tadpoles undergo metamorphosis.
b. Salamanders: Long bodies and tails, large in size, moist environment, some are entirely aquatic, lay egg in water, larvae forms, no metamorphosis.
c. Caecilians: Lost all of their limbs, burrowing, worm like, tropics.
Age of Amphibians: There was a time when amphibians ruled terrestrial habitats, it was before the reptile scene, when amphibians ruled terrestrial habitats. They grew to be very large and developed thick skin and body armor which means they must have depended on their lungs entirely. The rise of reptiles led to the decline of amphibians.
Lecture 22: (Know Pelycosaurs, Crocodiles, Alligators, Caimans, Velociraptors, Ostriches, Cassowaries, Rheas, Emus, Kiwis, Tinamous, Waterfowl, Owls, Parrots, Woodpeckers, Flamingos, and Penguins.)
Reptile perfect transition to terrestrial life: They had new leg arrangements, more efficient lungs and heart, and water tight coverings for skin and eggs.
Defining traits of reptiles: amniotic eggs, dry skin, thoracic breathing, and improved kidneys. Who are the amniotes: all that have amniotic eggs (bird, reptiles, mammals). Benefits of the amniotic egg: they're independent and eliminate the need for water since they contain a food source, have a water tight shell, and have 4 intermembranes. Internal fertilization: amniotic eggs make external fertilization impossible. So sperm has to hit egg before the membrane forms. Some reptiles and birds have external gestation though. Reptile Skin: Dry and watertight, made of keratin rich scales (keratin is also in hair, fingernails, and feathers but not homologous). Since not moist, they're entirely dependent on their lungs and therefore have an increased lung capacity.
Thoracic Breathing: glottal breathing limits breath to size of mouth (how amphibians breath). Thoracic breathing, only limited to size of lungs so greatly increases gas intake. Ectothermy vs. endothermy: ecto is when body temp changes with temp of environment. (can move in and out of sunlight to control body temp) and endo is when maintain their temp using internal body functions (need to maintain this temp in order to survive.
Benfits of reptile jaw: very strong, more efficient. We categorize them by the number of openings in the skull behind eyes.
Synapsids: Pelycosaurs, dominant, early, replaced amphibians. Long teeth, first terrestrial organism to kill and eat animals the same size.
Therapsids: May have had fur. Endothermic, short dominance, diverging away other groups, far more active.
Diapsids: Monophyletic group, contain all extant reptiles.
Archosaurs: Monophyletic, first animas to be bipedal, largest at time.
Dinosaur adaptations: Legs directly down underneath body, allows for speed, and agility, dominant.
Tuataras: Rare, (widespread Mesozoic era) off coast of New Zealand.
Lizards and Snakes (Squamates):carnivores, paired copulatory organs, limblessness (snakes) some venomous, sister tax to tuataras.
Turtles and Tortoises: aquatic and terrestrial, no teeth, sharp beaks, shelled. Fused vertebrate to top of shell, must lay eggs on land.
Crocodilians: Modern archosaurs, primarily aquatic, large, carnivorous, eyes and nostrils above snouts, large toothy mouths, strong necks, nests and parental care, travel inside parent’s mouths. How did birds evolve from their archosaur ancestors?:
Theropods: evolved feathers, gave rise to birds. Group of predatory dinosaurs. All had bipedal stance, hollow bones, swiveling wrists, 3 fingered hands and feet, and backwards pelvises. Example= Velociraptor.
What reptile traits to birds lack? Share?: The share feathers, flight skeletons, improved lung design, and endothermy, and they lack teeth.
Facts about feathers: they give lift for flight and provide heat. They're very flexible but strong b/c 2ndary branches hook together with barbs. Large ones also have think quills. Fanlike tail feathers stabilize the bird and down feathers keep it insulated.
Bird skeleton/Keels: bones are thin and hollow to help with flying. Many are also fused together, gives it a rigid skeleton which gives it a sturdy frame to support flying muscles. Muscles connect to keel for powerful flight.
Bird lungs: Provide a huge amount of oxygen, 1520 times faster, allows for more intake because flight takes a lot of oxygen and energy.
Endothermy in birds: body temp must be higher than in most mammals b/c it gives them good metabolism and ATP production. All the energy used for flight leads to heat loss. that's why their feathers are so insulating.
Beak and foot morphology: can tell a lot about a bird from its beak/feet. Example= you can tell a duck is aquatic from its webbed feet and filtering beak.
Paleognaths (Ratites): old jaw, flightless.
Neognaths: everyone else, new jaws.
Passeriformes (song birds): most successful, perching birds.
Lecture 23 (Know Echidna, Platypus, Whales and Dolphins, Bats, Koalas, Yapok, Wombat, and Virginia Opossum).
Why do mammals have a winning design?:
How do animals in very cold climates stay warm (two reasons)?: they're warm blooded (endothermic) and they have insulating fur.
Mammals live in highly variable habitats: Camoflauge
Mammals gain nutrients from many different sources: Milk from mammary glands, different food sources.
Details about monotreme biologyhow are they different from other mammals?: Size variation among mammals: Large variation, some are extremely small while others are huge.
Mammalian ancestors: Small, shrew like insectivores, confined to tree (aboreal) and nocturnal, large eyesockets.
Some mammals are extinct: Wolly mammals, sloths (giant ground), difficulties of being large. Five mammalian traits:
a. Hair: Homoplasious due to scales and feathers, all mammals, insulation, also blubber, hair acts as a camouflage as well. Undercoat prevents heat loss. Hair also a sensory structure, can be modified for defensive purposes like quills.
b. Mammary glands: All female structures, product milk, 50% of energy in milk comes from fat, milk changes as infant grows to accommodate needs
c. Endothermy: Control of own body temperature, homoplasious. d. Sweat Glands: Cooling mechanism via evaporation, important for endotherms so they don’t overheat, localized sweat glands, compensate with other cooling ways.
e. Four Chambered Heard: Facilitates efficient respiration, higher metabolic rates possible.
Placentas: Almost all mammals have placentas, internal gestation, allows for nutrient, water, and oxygen absorption and waste release.
Mammalian teeth: Highly specialized, omnivorous diet. newborns born w/o teeth so that they can nurse. Overall, we have very specialized teeth (grinding, ripping, chiseling). So looking at their teeth can often tell you a lot about their diets.
Herbivores’ gut syndrome: they have symbionts that allow them to better digest cellulose since we don't have the enzymes to do it. Increases plants nutritional value.
Hooves and horns: both made with Keratin. Hooves are specialized pads on mammals that run a lot. Can tell horns from antlers because antlers shed while horns are attached to the bone. Prototherians (monotremes) vs. therians: Prototherians are most basal group. Lay eggs and secrete milk through skin. Examples= Echidna (hair, quills, long sticky tongue, when egg hatches the baby burrows into hair on back) Platypus ( rubbery beak, hunts underwater through electric currents) while therians are most mammals who (marsupials) have short internal gestation therefore they finishing developing with mom and (eutherians) have highly developed babies, a long gestation.
Marsupials: Characterized by bearing live young, no shell develops, short gestation, born as tiny hairless and blind, usually in a pouch to suckle.
Eutherians: Most mammals are eutherians, much more developed babies. Eutherians diverged after the dinosaurs died out common ancestor, parallels with breakup of continents. David Attenbourough: The life of mammals.
Lecture 24: (Know Carpolestes simpsoni, Lemurs, Lorises, Galagos (Bush babies), Tarsiers, Tamarins and Marmosets, Squirrel monkeys, Howler Monkeys, Baboons, Rhesus Monkeys, Gibbons, Orangutans, Gorillas, Chimpanzees, Ardipithecus ramidus, Australopitchicus sp. Paranthropus sp. Homo habilis, Homo erectus, Homo neanderthalensis and Densovans and Homo Sapiens).
Two primate traits:
a. Grasping Hands (opposable thumbs): allow to grip (flattened nails), hang, swing, and use tools.
b. Binocular Vision (eyes in front of head): Overlapping allows for judgement of depth, distance.
Strepsirrhini: Wetnosed primate, first primates to diverge. Lemurs, galagos and lorises. Large eyes, good vision, nocturnal and arboreal with elegant movements and are almost herbivorous. Lemurs don’t act like the other groups, happy and hyper, not nocturnal and matriarchal. Haplorrhini: Drynosed primate, diurnal, color vision. Tarsier (similar to nocturnal ones). Very social, interact in large groups and have parental care.
Platyyhini (New World Monkeys): Flat spreading noses, arboreal, almost all have long prehensile tails.
Catarrhini: Haplorrhini that stayed in Africa. Old World Monkeys and hominoids. Downward pointing noses with nostrils down.
Old World Monkeys: no tail examples= baboons, rhesus monkeys.
Hominoids: Gibbons, Great Apes (humans). They're within Catarrhini, apes. Much larger brains and usually bodies than monkeys. In Asia and Africa, none ever in Australia, North/South America until migration of human species. Examples= Gibbons and Orangutans (1st to branch off, in Asia) Gorillas (diverged first to common ancestor with humans and chimps. African Ape), Chimps (diverged 2nd, also and African Ape, we have incredibly similar DNA to them). Humans must be great apes in order for great apes to be monophyletic: Hominins: Humans and their direct ancestors are hominins.
How have humans diverged from other apes?: We diverged from chimpanzees. Bipedalism: Hominins walk upright (separates us from everyone else) which gives us better view of our surroundings and allows us to carry things. Apes walk on knuckles and monkeys walk on palms.
Ardipithecus: “Ardi” May have been mostly arboreal, oldest we have, very complete, tree dwelling that could walk on feet, but she lacked arches. If comfortable in trees, she could use trees.
Australopithicines ( Australopithecus andParanthropus sp.): Australopithescus, small brains and small slender stature. Teeth similar to ours, sexual dimorphism (males a lot bigger) had pelvic, leg, and foot bone identical to humans. Famous example= Lucy, found in Ethiopia was after Ardi, showed that Hominins were out of trees and walking all of the time. Paranthropus was larger with heavier skulls, massive teeth, smaller brain cases but larger brain. Much more reliant on favorable environmental conditions.
Homo Species: All members of genus homo are called humans. Homo Habilis, 1st homo species that we recognize. Still had only 50% of our brain and a flatter face. They were short and had long arms. 1st fossils to be found with tools. Homo erectus replaced Homo habilis. Long limbed, 1.5 m tall. Had 75% of our brain and a much more human looking face. Probably able to talk (1st to do this!). Lived in small groups in caves (were the 1st hunter gatherers and the 1st to master fire and to leave Africa) were eventually found in Europe and Asia, lived on Earth the longest. Homo Neanderthalensis, also left Africa. They were short, stalky, and powerful. They loved in huts/caves, cared for their wounded, and burial rituals. Fossils of them showed that they
suddenly disappeared (replaced by us). Homo Sapiens, full language capabilities, 1st to make art, by 10,000 years ago we were the only homo species left.
Assimilation Hypothesis: homo sapiens interbred with other Hominins which led to extensive hybridization.
“Out of Africa” Hypothesis: Most supported hypothesis. Homo sapiens replaced all other groups. We evolved independently and didn't interbreed. There were 3 monophyletic groups, 3 migrations. This is supported b/c there's the most genetic variation in Africa.