11/2 - 11/6 Class Notes
11/2 - 11/6 Class Notes BIO 1500
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This 8 page Class Notes was uploaded by Diane Notetaker on Sunday November 8, 2015. The Class Notes belongs to BIO 1500 at Wayne State University taught by Daniel M. Kashian in Summer 2015. Since its upload, it has received 101 views. For similar materials see Basic Life Diversity in Biology at Wayne State University.
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Date Created: 11/08/15
November 2, 2015 Fungus-like Protists - Generally form net like structure to obtain food resources; decompose organic matter and will live where decomposing matter lives, aka in cool, wet places. - Plasmodium Slime Molds: they creep along about 2.5cm/hour – really fast! They move when feeding and digest things they can over run; single-cell organisms (multinucleate mass of cytoplasm with no cell walls or membranes); form reproductive spores when surroundings become unfavorable (dry-out); spores are dispersed by wind - Cellular Slime Molds: amoeba-like when feeding; when food is scare the single cells combine into bunches & differentiate to reproduce (early model of multi-cellularity) - Water molds: downy mildew is a protist! DM is a common, well-known food pest (contributed to Irish Potato Famine); fuzzy white growth; feed on dead organisms or parasitized plants; asexual reproduction with motile zoospores with 2 unequal flagella Ecological Diversity of Protists They’re pathogens, predators & filter feeders, decomposers, symbiotic, and primary producers. How to Protists Reproduce? What is significant about each phase? Why are they different? What are the outcomes? - Both mitosis and meiosis are continuous, so the phases do run together. - Remember to think about what is significant about each phase, how are mitosis and meiosis different, and what are the outcomes of each. You do not necessarily need to memorize each step. Asexual reproduction through Mitosis: - It is nuclear division plus the division of the cytoplasm. 1. Interphase (prior to mitosis): DNA replication; duplicate centrosomes (organelles that regulate cell division) move to opposite sides of nuclear envelope 2. Prophase: spindle fibers (protein structure that divides genetic material) form around centrosomes; chromatids (condensed chromatin, one copy of a newly copied chromosome) become visible; there are one pair of chromatids per chromosome. 3. Prometaphase: nuclear envelope breaks down; spindle fibers attach to kinetochores (location where chromatids will be pulled apart); kinetochores begin to line up. 4. Metaphase: kinetochores are line up along equatorial plate; chromatids separate and start to move towards opposite poles 5. Anaphase: separated chromatids are on opposite sides of cell to allow cell to divide and for each daughter cell to have genetic material; if they don’t migrate properly, the cells won’t have full compliments of chromosomes and that could lead to development diseases. 6. Telophase: reformation of nuclear envelopes. 7. Cytokines: cells divide and now you have two (2) daughter cells with identical genetic material What is the boring biological definition of sex? The process of reproducing offspring through an alternation of fertilization (producing diploid cells) and meiotic reduction of chromosome number (producing haploid cells). Remember what haploid and diploid mean! haploid = when cell has half the usual number of chromosomes diploid = when cell has two complete sets of chromosomes, one from each parent - Further explanation here: https://www.youtube.com/watch?v=1yu1Zuy_uEQ - Refer to diagram on lecture slides of the general depiction of the alternation of generation cycle between haploid (n) and diploid (2n). syngamy = the fusion of two cells, or their nuclei, in reproduction Do humans have alternation of generations? Yes, but our haploid phase is reduced to only occur in our sperm and eggs. Sexual Reproduction through Meiosis: - In “higher organisms” meiosis (haploid generation) occurs exclusively in gonads; testes and ovaries (animals) or anthers and ovaries (plants) - Gametes are produced by meiosis in a special population of cells called germ line cells. Meiosis 1 1. Prophase 1: homologs (homologous chromosomes, the chromosome pairs, i.e. chromosome 3 from mom, chromosome 3 from dad) align 2. Metaphase 1: chromosomes are lined up; now that they’re next to each other they can exchange genetic material (by means of crossing over) 3. Anaphase 1: chromosomes separate and move to opposite poles; at this point, the chromatids are still attached 4. Telophase 1: homologs go to separate poles, each with two chromatids that remain attached; now you essentially have a pair of cells Meiosis 2 1. Interkinesis: DNA has not yet replicated; this is important because if the DNA were replicated at this point, you’d have diploid gametes 2. Prophase 2: chromosomes condense 3. Metaphase 2: kinetchores line up along equatorial plate (similarly to how they did in mitosis) 4. Anaphase 2: chromatids separate and pull to opposite poles 5. Telophase 2: homologs go to separate poles, each with two chromatids that remain attached – four (4) cells from your one parent cell each with distinct genetic material Why is each of the 4 daughter cells different from the other genetically? a) Independent assortment: During metaphase 1, homologous chromosomes match up along the equatorial plate in a random orientation – sometimes mom’s chromosomes is on the left, sometimes on the right. During anaphase 1, the homologous chromosomes are pulled apart where those on left will be put into one daughter cell and those on right will be put into another. In this way, generally, genes on the same chromosome are inherited together. But that can be shaken up by crossing over… b) Crossing over: a DNA strand can break up and exchange chunks from one homologous chromosome to another. The point at which this occurs is called a chiasmata. Refer to diagrams of cross-over on lecture slides for visualization. Why have sex? - Asexual reproduction can produce a lot of new individuals - Sexual reproduction is expensive in terms of energy (expend energy to make gametes, dangerous to have sex), but can create a great amount of genetic variation that may be advantageous to a species in a changing environment. - Genetic diversity increases evolutionary potential, and enhances survival against diseases General characteristics of Eukaryotes - larger in size, have cytoskeleton that allows structure and flexibility, have nucleus and organelles that compartmentalizes functions allowing for diversification of cell function, have diploid linear chromosomes which allow for mitosis and meiosis, and loss of cell wall with thinner outer membrane General characteristics of Animalia - heterotrophic: obtain energy & organic molecules by ingesting other organisms herbivores: consume autotrophs carnivores: consume heterotrophs detritivores: consume decomposing organisms omnivores: will consume all of the above, anything they need to - multicellularity: allows for more complex bodies, generate different tissue types - tissue systems: cells are organized into structural and functional units (except in sponges) - active movement: directly related to the evolution of nerves and muscles; most can move, even sessile animals can move limbs (except sponges) - reproduce sexually: cells form in meiosis functions as gametes, haploid cells first fuse to form zygote - embryonic development: zygotes undergo mitotic divisions (cleavage), most embryo kinds develop into larva - no cell walls = more flexibility - have diversity in form: lots of different sizes, most lack backbone - diversity in habitat: live almost anywhere! The Animal Body Plan – 5 Key Transitions 1. Tissues a. Parazoa (sponges) do not have defined tissues and organs, but can dedifferentiate their cells to change function. The body of the sponge is a closed-end tube that is lined with choanocytes which move water through the tube, capturing and engulfing food particles. The choanocytes can transform into sperm cells for sexual reproduction. It is rare for an organism to be able to dedifferentiate cells. This suggests that cell specialization carries an evolutionary advantage; those who could dedifferentiate did not persist through time. b. Eumetazoa (all other animals) have well-defined tissues, and maintain irreversible differentiation of cell types. Once tissues have taken a form, they can’t change. November 4, 2015 What is a body plan? - A group of structural and developmental characteristics that can be used to identify a group of animals, such as a phylum. Remember, though, that there are exceptions to every rule. - All members of a particular group share the same body plan at some point during their development (embryonic, larval, or adult stage) The Animal Body Plan – 5 Key Transitions (con’t) 2. Symmetry - Parazoa (sponges) lack definite symmetry; Eumetazoa (all other animals) have a symmetry defined along an imaginary axis drawn through the animal’s body a. Radial symmetry: if you cut along various plans, the halfs will be similar to each other; body parts arranged around central access Cnidarians (jelly fish & hydra & allies): carnivores who use nematocysts to capture prey; have two body forms – medusa (like a jelly) or polyps (like a hydra), and others can alternate between the two depending on life phase b. Bilateral symmetry: body has right and left halves that are mirror images (not front to back, nor top to bottom). What is the advantage? It allows for greater mobility, an organism can move through the environment in a consistent direction; allows for anterior cephalization, a definite brain area & central nervous system (a concentration of nerve cells) can be formed that controls peripheral nerves throughout the body. In contrast, other organisms have something like a nerve-net that is not concentrated in one part of the body. 3. Body Cavity - Parazoa (sponges) have no germ layers (layer of cells that eventually give rise to tissues and organs); Cnidarians (jelly fish) and ctenophores (comb jellies) are dipoplastic with two layers and no organs; Eumetozoa (all other animals) produce three germ layers. a. Outer: ectoderm becomes body covering and nervous system b. Middle: mesoderm becomes the skeleton and muscles c. Inner: endoderm become digestive organs and intestines - The production of these three layers results in a body cavity, which is a space surrounded by mesoderm tissue that is formed during development. A true coelom (body cavity) occurs in the mesoderm. It is filled with liquid or gas Helps distribute food, wastes, hormones, etc. from one end of the animal to the other It is responsible for hydrostatic skeletons where you use water pressure to pump up the cavity and make it rigid Where organs are supported and accommodated - Body cavities have evolved multiple times which has resulted in several forms. a. Aceolomate: no body cavity in the mesoderm (flatworms) b. Pseudoceolomate: body cavity between mesoderm and endoderm, aka the pseudocoel (roundworm) c. coelomates: body cavity entirely within the mesoderm (earthworms) 4. Pattern of development - Eumetazoa (Bilaterian – all other animals) go through mitotic cell divisions of the egg form a hallow balls of cells called a blastula. The blastula indents to form a two-layer thick ball with a blastopore (opening to outside) and an Archenteron (primitive body cavity). Bilaterians can then be divided into two groups: a. Protostomes: develop the mouth first from or near the blastopore (most Bilateria) b. Dueterostomes: develop the anus first from the blastopore (humans! & sea cucumbers & seahorses). Differ from protostomes in three embryological features: Cleavage pattern – when cells of the Protosome embryo are cleaved, the new cells are rotated off-center from parent cells in a spiral pattern; Dueterostomes are cleaved in a radial pattern where the newly formed cells maintain the same axis as the parent cells Developmental fate – protostomes are determinate, the final outcome of the cell cannot be altered, if one cell is changed, the embryo will not develop normally; dueterostomes are indeterminate and development can continue if disturbed, the other cells will continue to divide Formation of the coelom – in protostomes the coelom forms directly from a splitting of the mesoderm; in dueterostomes the coelom forms indirectly from the archenteron (primary body cavity) - Quick & Concise video on Protostomes vs. Dueterostomes: http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078695104/3839 22/ch24.swf::Visualizing%20Protostome%20and%20Deuterostome%20Development 5. Segmentation - Allows for redundant systems; think about annelids (earth worms), they can survive when cut in half - Allows for improved locomotion by being more efficient and flexible; each segment can move semi- independently - Consists of a linear array of compartments that look alike, at least in the embryo; this underlies the body organization of most morphologically complex animals - Humans are segmented; the human embryo at some points looks like a series of other animals - Segments can also specialize *See Phylogenetic Relationship figure in lecture slides Among Protostomes we’ll look at… - Spiralians (spiral development) Platyzoa Platyhelminths (flatworms): bilateral asymmetry, no body cavity, no organs for O2 transport to internal tissues, often parasitic Rotifers: bilateral asymmetry, psuedocoelemate, are tiny and look like ciliated protists, but possess developed internal organs Bryozoa: colonial – live in groups together (like coral), have sexual and asexual forms, have lophophore (a ridge of cells around mouth that bears tentacles for feeding) Brachiopoda: 4-9cm large, mainly marine, bottom dwellers, look like mollusks superficially Lophotrochozoa Annelids (earthworms): live in all environments, segmented for improved locomotion, possess separate nerve center (ganglia) for each segment Molluscs: loss segmentation, diverse body plans yield different body forms (octopi vs. bivalve clam) - Ecdysozoa (molting animals): have external skeletons and increase in size by molting. Skeletons are made of cuticle (worm-like organisms) or chitin (anthropods) Nematodes (roundworms): exchange O2 and obtain nutrients through thick cuticle and intestine, are predatory/parasitic, one of the most abundant animal groups Arthropods: most abundant animals on the planet because of the development of chitin – a strong, flexible, waterproof polysaccharide; chitin allowed them to better utilize terrestrial environments by maintaining water, preventing dehydration; exoskeleton provides protection; improved mobility and control by evolving appendages through muscular attachments to exoskeleton Trilobito: once dominant in the marine environment, but now extinct; heavily armored & with jointed appendages Chelicerates (spiders): abundant, important predators, body has two parts – anterior has four pairs of jointed appendages Crustaceans (lobsters, pill bugs): dominate marine arthropod but some are terrestrial; body divided into 3 sections – head fused with five pairs of jointed appendages, often with specialized legs thorax, abdomen Uniramia: mostly terrestrial, body divided into 2 or 3 sections November 6, 2015 *Refer to first phylogenetic tree in lecture slides for reference on evolutionary relationship of the groups discussed here. Who has a coelom? a. Aceolomate: no body cavity in the mesoderm (flatworms) b. Pseudoceolomate: body cavity between mesoderm and endoderm, aka the pseudocoel (roundworm) c. coelomates: body cavity entirely within the mesoderm (earthworms) Generally, acoelomates evolved first. They are found in Porifera (sponges), Cnidaria (hyrda), and Ctenophora (comb jellies). Protosomes including lophotrochozoans and platyzoans may also be aceolomates. Developed later, psuedoceolomates can appear in protostomes lophotrochozoans, platyzoans, and ecdysozoans. Developed latest were the coelomates. Lophotrochozoans, platyzoans, and ecdysozoans can also be coelomates. All deuterostomes are coelomates. *Refer to the tree, it’s easier to understand that way. - Did the ancestor to Protostomes and Deuterostomes have a coelom? Yes, the ancestor is coelomate and acoelomates re-evolved in Protostomes. - How might you explain the presence of aceolomates in Spiralia and earlier animals (e.g. Porifera)? There could have been a secondary loss of the coelom, thus yielding coelomates. The loss of a coelom would be an analogy because it cannot be traced to a common ancestor, aka convergence. - How would you lose your coelom? First, let’s think about why organisms have a coelom. To organize and protect organs. They have organs because their bodies are big and complex, and oxygen and other nutrients need to be distributed efficiently. Organisms like Platyhelminthes (flatworms) are quite reduced, are parasitic, and don’t have the same need as a more complex organism. Coeloms would be costly to maintain. - Species do NOT always become more complex! Often environments yield less complexity, i.e. cave-dwelling organisms lose eyes. Vestigial structures are attributes that had function in an ancestral organism, but has no function today, i.e. hip bones in a whale. - How may have the pseudocoelomate occurred? This may be an occurrence of convergence and have evolved as many as three separate times. Deuterostomes - Composed of Echinodermata and Chordata; they are abundant, visible, contain lots of diversity, and live in most available habitats. Humans are Deuterostomes. - Echinodermata (sea stars, sea urchins, sand dollars) and Chordata (fish) look very different, but share common development features. Echinodermata have a water vascular system that includes tube feet for movement, feeding, and breathing have calcified internal plates which make them hard and provide protection reproduce asexually and through regeneration (if one breaks in half, each piece can keep living) Protochordates Hemichordata (acorn worms): burrow in marine sediments; have unique feeding habits Urochordata (tunicates): tad-pole like larvae; have dorsal, hallow nerve chord, have short notochord Cephalochordata (lancelets): burrow in marine sediments; capture food with mouths; have complete nerve chord and complete notochord Vertebrates (Chordates) moved from marine environments to freshwater, and then to land vertebral column provides strength and greater ability to move an improved circulatory system is necessary for more activity have fins, jaws, lungs, and amniotic egg Jawless fishes: an opening with grasping like structure; mainly deep-sea organisms; some with tongue Evolution of Jaws have brachial basket composed of different bones; between there are openings called gill slits where water is taken in by mouth and passes out through gills each gill is composed of filaments where oxygen exchange occurs over time, rods fuse with cranium and each other, eventually forming jaws Our jaw bones are homologous with the first gill arch in jawless fish; now we can eat a greater diversity of food! True or False? According to phylogenetic tree, the ancestor of all chordates invaded from freshwater. False. True or False? According to phylogenetic tree, tetrapods evolved once. True. They only appear once on the tree. True or False? According to phylogenetic tree, lobe-finned fishes are more closely related to lungfish than they are to tetrapods. False. They are the same distance away, they share the same common ancestor. Note the points where animals invaded freshwater systems. Chondrichthyes (Cartilagenous Fish) their skeletons are made out of cartilage; then bone developed. This allows for more strength and flexibility developed lateral line = a series of holes alone the length of the body; they are specialized cells that are connected to nerves in the central nervous system; they are sensitive to vibration in water. Just like our ears pick up vibration, chondrichthyes use lateral lines to hear/feel. Are lateral lines homologous to ear drums? No. Actinopterygii & Sarcopterygii (boney fish) Ray-finned fish (Actinopterygii) have rays/spines radiating from body Lobe-finned fish (Sarcopterygii) have a bony protrusion that supports the fin This is a significant difference because the bony protrusion is an early hand. It is a homologous to tetrapod digits, allowing them to utilize land. What’s significant about getting up on land? You can get away from predators, and there was a lot of food out there that other’s weren’t taking advantage of. Amphibians fully developed legs lungs as well as cutaneous circulation where they can absorb oxygen through their skin have modified circulatory system with pulmonary veins and partially divided heart (necessary when living out of water) typical life cycle: begin as aquatic eggs (jelly-like), often larval stages that require water, then go through metamorphoses to an adult form Amniotes includes mammals, reptiles, and birds significant distinguishing feature: amniotic egg – they don’t depend on water for offspring like amphibians do The amniotic egg is composed of a shell containing an embryo Reptiles: many are extinct, but survived by lizards, crocodiles, etc. They have dry skin and breath through thoracic cavity into lungs; Reptilia is not a real taxonomic group because all descendants do not come from a common ancestor Birds Why aren’t birds considered reptiles? Feathers are considered homologous structures to reptile scales. They have modified skeletons that are very light which enables flight Efficient circulation allows for high metabolism that is necessary for flight Endothermic = ability to keep themselves warm, maintain constant temperature so metabolism is constantly at high rate (unlike reptiles that need to warm themselves) Mammals Endothermic Have hair that’s useful for insulation and camouflage Have mammary glands and most have placenta Monotremes: lay shelled eggs Marsupials: have pouch where embryo develops Placental: give live birth Let’s think about the timing of these evolutionary events - the age of the earth is 4.5 billion years - life originated 3.8BYA. It’s been around for a long time before it developed complexity. - Why did it take so long? Perhaps it’s due to oxygen levels on earth. See figure in lecture slides. Organisms needed more oxygen to be able to support more metabolism and complexity. - Why did oxygen begin to build up? Plant evolved! Thank you photosynthesis.
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