Ecology, Week 3
Ecology, Week 3 LIFE 320
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This 6 page Class Notes was uploaded by Rheanna Gimple on Monday September 19, 2016. The Class Notes belongs to LIFE 320 at Colorado State University taught by Dale R Lockwood in Fall 2016. Since its upload, it has received 7 views. For similar materials see Ecology in Biology at Colorado State University.
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Date Created: 09/19/16
Biomes Facet of Ecology: Natural History o Fundamentally descriptive o Study how organisms influenced by climate, soils, predator, competitors, and evolutionary history o Another example of natural history is most of genomics: Natural history of genome Describing genetic patterns Species range o Species have range of conditions over which they can survive Edaphic factors: properties of soils (i.e. moisture, geologic origin, etc.) that influence plants o Species perceive quality of conditions from optimum to poor I.e. sugar maple found around great lakes due to weather and soil conditions o Species independently distributed Drier to wetter environments have species overlap but not clustered together Biomes: major vegetation divisions o Influenced by physical properties of the environment o Simplify to generalize, but no two ecosystems are exactly alike Goal is to capture Explain similarities and differences among Convergence o Organisms evolve similar traits in response to common environmental conditions: Organisms may be unrelated, or related But evolutionary response is independent o Similar adaptive responses emerge in response to particular selective conditions I.e. mangroves - thick, leather leaves, root projections, viviparity Condition/place not plant Convergent evolution Can be different families genetically w/ diff. evolutionary pathways, but are similar due to similar environments Biome concept o Character of natural of natural communities is determined by climate, topography and soil: physical factors o Because of convergence, similar dominant plant forms occur under similar conditions o Biomes are categories that group communities by dominant plant forms o Life is not so simple Interactions of many kinds, chance, history also critical in determining the distribution/abundance of organisms o Annual precipitation and average temperature are basic factors for biomes When temp changes and rain comes is also important Tundra o Cold and dark much of year o Arctic tundra encircles earth just south of ice-covered polar seas in N Hemisphere Covers about 20% earth's land surface o Arctic tundra has extremely long, cold, and harsh, short summers (6/8 weeks) o B/c rainfall amounts to only about 20 cm a year, tundra could possibly be considered desert Coniferous forests - dominated by gymnosperms o Coniferous forests are found in 3 locations Taiga Near mountaintops Along pacific coast of N America Temperate deciduous forests have abundant life o Temperate deciduous forests Found S of Taiga in E. N. America, E. Asia, and much of Europe Seasons well defined, and growing season ranges between 140 and 300 days Temperate grasslands have extreme seasons o Temperate grasslands Include Russian steppes. S. American pampas, and N. America prairies Bitterly cold winters and hot dry summers Savannas - grasslands in tropics o Savannas - in regions where a cool dry season is followed by hot rainy season Largest savannas in Central and S. Africa Others in Australia, SE Asia, and S America Deserts o Deserts usually found at latitude of about 30 degrees in both N and S hemispheres Winds that descend in these regions lack moisture, and the annual rainfall is less than 25 cm Days are hot because of lack of cloud cover - allows sun to penetrate easily Night cold because heat escapes easily into atmosphere Tropical rainforests are warm with abundant rainfall o Tropical rainforests of S America, Africa, and Indo-Malayan Temperature always warm (20-25) Lots of rain (min 190 cm/yr.) o May be richest ecosystem Diversity of species is enormous Topography and other effects also influence climate o Topography: surface of land Mountains are topographic features that affect climate, and distribution of ecosystems Difference between the windward side and the leeward side can be dramatic Ex: Hawaiian Islands Windward receives more than 750 cm of rain a year Leeward side, which is in a rain shadow, gets on the average only 50 cm of rain and is generally sunny Going up in altitude very similar to going north o Nearby bodies of water Ocean Temperature is more stable than landmasses Ocean water gains or loses heat more slowly than terrestrial environments Monsoon climate - wet ocean winds blow onshore for almost half the year o Important trivia What is land surface area of the earth: 150 million km2 What biomes occupy most land area Moisture gradient: mesophytic forest -> oak-hickory forest -> oak woodland -> prairie -> dry grasslands -> desert Temperature gradient: tropical forest -> subtropical -> temperate deciduous ->temperate mixed-boreal forest -> tundra Aquatic ecosystems o Aquatic ecosystems vary in size, physical properties, and biological systems o Key components to consider: Light Depth: less light penetrates the farther down you go Temperature Movement (currents, tides) Oxygen content (determined by latter two) Productivity Amount of photosynthesis Dissolved salts o Streams Pools Tend to have more life than places with strong currents Riffles o Lakes Basins that collect water Physical features: Stratified (layered) with respect to Light penetration Temperature Temperate lakes cold water sits on bottom w/ sharp divide b/t warm water on top Oxygen biological activity is also stratified in water o Lakes Ponds and Oceans Littoral zone: In lakes: shallow area at edge with rooted vegetation In oceans: region between high and low tides Limnetic zone: open water, gets enough light for photosynthesis Benthic: sediments and subsurface layers below limnetic o Oceans Littoral zones: shallow area at edge = intertidal Neritic zone: beyond low tide zone out above continental shelf Oceanic: past continental shelf Photic: with light for photosynthesis Aphotic: insufficient light, depends on nutrient rain Pelagic zone: region of ocean not near shore on the bottom Demersal zone: region of water near and influenced by benthos (benthic zone) Intertidal zone: Rocky intertidal has more complexity than typical intertidal Tide pools Coral reefs Similar to biodiversity of rainforests Vertical structures Different light levels Pelagic zone Very stratified- not really nutrient upwelling A lot of animals move through zone to get calories Move great distances Demersal zone Mostly invertebrates Streams and rivers Key features: Move High oxygen Depend on movement, temperature, pollution Dissolved nutrients and sediments come from land Light varies River continuum Organic matter and nutrients come from headwaters Streams are primarily allochthonous - production dominated from outside material Nutrients 'spiral' downstream to rivers Rivers primarily autochthonous - algae dominate production (fed by nutrients) Water warmer and slower Estuaries at mouths of rivers Brackish waters (part salt part fresh) One of most productive habitats on earth Nursery for many fisheries from crabs to fishes Antarctica only continent with no river systems Australia has 1 Evolution evolution: change in allele frequency in a population from one generation to the next macroevolution: large-scale changes that lead to speciation or higher level diversification o Large scale patterns in nature microevolution: small-scale changes within populations over time o Underlying processes and mechanisms Gene: Sequence of DNA that species cell structure, including proteins and several types of RNA o Genes do not always produce the same phenotype: gene regulation and modification is important Allele: an instantiation of a gene 4 mechanisms of evolution o Selection o Genetic drift Random changes in allele frequencies from one generation to the next Larger impact on small populations All alleles either go to fixation or loss eventually If operating only under drift Reduces genetic diversity o Mutation Basic source of novel variation Increases genetic diversity o Migration Increases diversity as gene flow enters a population Natural selection o Evolution by natural selection described by Darwin and Wallace o Mechanism eluded them Mendel's paper was forgotten for years o 4 postulates of evolution by natural selection Individuals within a population show variation in a trait Some of the variation is inherited by offspring (heritable) Individuals have differential reproductive and survival success Survival and reproduction are not random with respect to the trait: individuals that survive and reproduce have the most favorable variations o Selection directional selection (incomplete dominance) One allele is favored Allele is driven to fixation with the loss of other alleles Favors one extreme balancing selection (over dominance) Heterozygote is more fit than either homozygote Ex: sickle cell anemia Both alleles are maintained in population Favors average traits disruptive selection (under dominance) Heterozygote is less fit than homozygote Don’t see very often Favors both extremes Properties of populations o Population is a group of organisms of the same species that share a specific area o Populations evolve in response to natural selection o Study of natural selection will provide foundation for studying population ecology Ex: finches on Galapagos islands Bigger beaked birds eat bigger seeds, smaller beak depth smaller seeds Population correlates with seed abundance Harder seeds select for bigger beak size Wetter season lots of small seeds produced As environment changes so does selection Natural Selection o Genotype: the genetic makeup of an individual o Evolution: changes in genetic makeup of a population o Natural Selection: if well suited to environment organism tends to have more offspring Can help drive adaptations in an environment Phenotypic plasticity: modifies organisms over time based on phenotype Genetics and environments go hand in hand
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