Chapter 3 Evolution and Ecology PDF

3 – EVOLUTION, ECOLOGY, & ANIMAL BEHAVIOR 3.1 Evolution Evolution is the change in allele frequencies from generation to generation. Lamarck proposed an incorrect theory of evolution involving the inheritance of acquired traits. For example, a giraffe stretching its neck in length...

3 – EVOLUTION, ECOLOGY, & ANIMAL BEHAVIOR 3.1 Evolution Evolution is the change in allele frequencies from generation to generation. Lamarck proposed an incorrect theory of evolution involving the inheritance of acquired traits. For example, a giraffe stretching its neck in length during its lifetime would have progeny with longer necks. Darwin proposed a theory of evolution (he referred to it as “descent with modification”) that relied on natural selection as its mechanism. Hardy Weinberg Equilibrium Allele frequencies remain constant in a gene pool for a population in equilibrium. Hardy-Weinberg Assumptions 1. No mutations 2. No gene transfer (no immigration/emigration) 3. Random mating 4. Large population size 5. No selection (natural or otherwise) p+q=1 p = frequency of dominant allele q = frequency of recessive allele p2 + 2pq + q2 = 1 p2 = frequency of homozygous dominant genotype 2pq = frequency of heterozygous genotype q2 = frequency of homozygous recessive genotype If 9% of rodents in a population in equilibrium have white fur (recessive) and 91% have brown fur (dominant), what percentage of the population are heterozygous for fur color? ChadsPrep.com 52 Five Agents of Evolutionary Change 1. Mutation 2. Gene Flow – movement of alleles from one population to another 3. Nonrandom Mating Assortative Mating – Occurs when phenotypically similar individuals mate Inbreeding –increased likelihood of mating between closely related organisms (decreases phenotypic variation) Disassortative Mating – Occurs when phenotypically different individuals mate Outbreeding - increased likelihood of mating between genotypically different organisms (increases phenotypic variation) 4. Genetic Drift - Random change in allele frequencies in a population Small populations are more susceptible to genetic drift. Bottleneck Effect Founder Effect A dramatic decrease in size of a Occurs when an isolated population has population making it susceptible only a few individuals as its founders, and to genetic drift the allele frequencies in the founders are not representative of the source population from which they come 5. Natural Selection – Individuals with greater fitness leave behind more progeny. Fitness is a combination of survival, mating success, and number of offspring per mating. Requirements for Natural Selection 1. Phenotypic variation 2. Phenotypic variation results in a difference in fitness. 3. Phenotypic variation is heritable. ChadsPrep.com 53 Natural Selection Sexual Selection – Selection with respect to mating success Negative Frequency-Dependent Selection – Occurs when rare phenotypes are favored; maintains variation Positive Frequency-Dependent Selection – Occurs when common phenotypes are favored; reduces variation Oscillating Selection – Which phenotype is favored changes with the environment Disruptive Selection – selection against intermediate phenotypes Directional Selection – selection against one extreme in an array of phenotypes Stabilizing Selection – Selection against the extremes in an array of phenotypes ChadsPrep.com 54 The Evidence of Evolution 1. Microevolution – Beak size in Galapagos finches Peppered moths and industrial melanism 2. Artificial Selection – The selection by humans for desirable traits in domesticated animals and crops and by scientists in the laboratory demonstrate that selection can lead to evolutionary change. 3. Fossil Evidence 4. Anatomical Evidence – Homologous structures reveal common ancestry. Homologous structures are derived from a common ancestor. Early embryonic development reveals similarities amongst species. Vestigial structures have no apparent function, but resemble structures found in other species hinting at common ancestry. 5. Convergent Evolution and the Biogeographical Record Convergent evolution occurs when two species possess the same analogous structures not derived from a common ancestor (such as wings in birds vs bats). The biogeographical record suggests parallel evolutionary adaptations as the result of similar selective pressures in similar, yet distant, environments. ChadsPrep.com 55 Speciation Species – groups of interbreeding populations which are reproductively isolated Microevolution – evolution within a species i.e. adaptation Macroevolution – evolution leading to the creation of new species MECHANISMS OF REPRODUCTIVE ISOLATION PREZYGOTIC Ecological Isolation – Species occupy different habitats. Behavioral Isolation – Species differ in mating behaviour. Temporal Isolation – Species reproduce in different seasons/times of day. Mechanical Isolation – Structural differences prevent mating. POSTZYGOTIC Hybrid Inviability/Infertility – Hybrid organisms don’t survive or are infertile. Allopatric Speciation – speciation between geographically separate populations Sympatric Speciation – speciation between populations in a single locality 1. Via polyploidy 2. Via disruptive selection Adaptive Radiation – Rapid evolution of related species from a common ancestor with adaptation to different parts of the environment. Key Innovation – a new trait that unlocks previously inaccessible aspects of the environment Character Displacement – adaptation that minimizes competition for resources Gradualism – Evolution proceeds slowly with the gradual accumulation of changes. Punctuated Equilibrium – Populations experience long periods of stasis (little to no evolutionary change) punctuated by rapid bursts of evolutionary change. ChadsPrep.com 56 Systematics and Phylogenies Systematics – the study of evolutionary relationships Phylogeny – evolutionary tree CLADISTICS A method of classification of organisms into groups (clades) with the hypothesis of common ancestry based upon commonalities, the greater the commonalities, the more recent the common ancestor. In cladistics, characters (i.e. traits) are assigned as being either ancestral or derived. Ancestral Characters inherited from the most recent common ancestor Character relative to the group being examined. Characters only shared by a subset of the group being examined Derived and thereby concluded not to have been inherited from the Character most recent common ancestor. Synapomorphy Shared derived character (homologous) Symplesiomorphy Shared ancestral character (homologous) The phylogeny that requires the fewest evolutionary events is Parsimony best. Shared derived characters not from a common ancestor Homoplasy (analogous characters that are the result of convergent evolution) Monophyletic A group that includes the most recent common ancestor and all Group descendants (a.k.a. clade). Paraphyletic A group that includes the most recent common ancestor but Group not all descendants. Polyphyletic A group that does not include the most recent common Group ancestor. ChadsPrep.com 57 3.2 Ecology Population Ecology Range – A population’s geographic distribution Dispersion – How individuals in a population are distributed in the environment DISPERSAL MECHANISMS Windblown Fruits Dispersed by wind Adherent Fruits Dispersed by adhering to animals Fleshy Fruits Dispersed by being eaten/defecated by animals Lizards Suggested that they or their eggs have floated on vegetation Bats Only flying mammals SPACING PATTERNS Random Occurs for populations without strong interactions with one another Uniform Often the result of competition Clumped Often due to uneven distribution of resources, defense against predators, or due to having greater concentrations in the center of a populations’ range and lower near the edges of the range. Metapopulations – Distinct populations that may exchange members. Most often occur when suitable habitats are patchily distributed. Population Dynamics and Demography Population Dynamics – change in a population over time Population Demography – quantitative study of populations Sex Ratio – ratio of males to females in a population Generation Time – average time from birth to having offspring Cohort – a group of individuals of the same age Age Structure – The relative number of individuals of a population in each cohort. Fecundity Rate – birth rate Mortality Rate – death rate ChadsPrep.com 58  SURVIVORSHIP CURVES Higher mortality rates later in life Type I Ex. Humans, large mammals Individuals are equally likely to die at any age Type II Ex. hydra, lizards Many offspring, few of which survive to reproduce or beyond Type III Ex. oyster, fish, insects Cost of Reproduction – Reduction in future reproduction due to current reproduction Number of Offspring vs Investment per Offspring Semelparity – All reproductive resources are focused on a single large event. Iteroparity – Offspring are produced multiple times in a lifespan. Biotic Potential – maximum rate of population growth Carrying Capacity – maximum population supported by the environment Density-Dependent Effects – Effects due to the size of the population that affect reproduction and/or survival (negative feedback vs positive feedback) Density-Independent Effects – Effects NOT due to the size of the population that affect reproduction and/or survival such as harsh weather or natural disasters r-Selected vs K-Selected Populations r-Selected K-Selected Lifespan Short Long Age at 1st Reproduction Early Late Maturation Time Short Long Mortality Rate High Low Offspring per Reproductive Event Many Few Reproductive Events per Lifetime Few Many Parental Investment Low High Size of Offspring/Eggs Small Large Population Stability Low High ChadsPrep.com 59 Community Ecology Community – The species present at a particular location. Ecological Niche – the sum of resources used by an organism from its environment and the conditions thereof Fundamental Niche – the entire potential niche a species could use/occupy Realized Niche – the actual niche a species uses/occupies Interspecific Competition – Competition between species for the same resource Principle of Competitive Exclusion (Gause) – In competing for the same resource, the species that uses it more efficiently will eliminate its competitor from their location. Resource Partitioning – Occurs when a niche is divided in order to avoid competition. Predation – the consumption of one organism by another Coevolution – Occurs when adaptations in one species result in adaptions in another species with which it interacts which can in turn result in further adaptations in the first species. Coevolution is commonly observed between an animal and its food source such as between herbivores and the plants they consume and between predators and their prey. Warning Coloration – Poisonous animals are often brightly colored as a way of advertising that they are poisonous. Batesian Mimicry – Mimicry in which a palatable species resembles a distasteful/poisonous species resulting in protection from predation. Mullerian Mimicry – Mimicry in which multiple distasteful/poisonous species resemble one another. The result is that a predator will more quickly learn to avoid these species. ChadsPrep.com 60  SYMBIOSIS -Long term interaction of two species to the benefit of one or both Mutualism Symbiotic relationship between organisms in which both benefit Symbiotic relationship between organisms in which one benefits while the other is harmed Parasitism Ectoparasites – external parasites Parasitoids – Insects that lay eggs in living hosts Endoparasites – Internal parasites Symbiotic relationship between organisms in which one benefits Commensalism but the other is neither benefited nor harmed Succession Succession – The process by which the biological community and habitat in an area changes over time Secondary Succession – Succession occurring following a disturbance to an existing community (ex. a fire in a wooded area). Primary Succession – Succession occurring in a lifeless (abiotic) area where there had been no existing community (ex. rocks exposed by glacier retreat or new volcanic islands). STAGES OF SUCCESSION Growth of pioneer species such as lichens or mosses (r- 1. Establishment selected). These alter the habitat over time making the future growth of additional species possible. Growth of less weedy species and overall increase in species 2. Facilitation richness. A further increase in species richness may ultimately lead to a decrease as K-selected species often out-compete r-selected 3. Inhibition species. The final stable community is called a climax community. ChadsPrep.com 61 Ecosystems Ecosystem – All organisms + abiotic environment at a particular location. BIOGEOCHEMICAL CYCLES Carbon Cycle Water Cycle Nitrogen Cycle Phosphorus Cycle AUTOTROPHS AND HETEROTROPHS Organisms that synthesize organic compounds from AUTOTROPHS inorganic precursors Photoautotrophs Autotrophs that use light as their energy source Autotrophs that use inorganic oxidation reactions as their Chemoautotrophs energy source Organisms that cannot synthesize organic compounds HETEROTROPHS from inorganic precursors but ingest organic compounds by consuming other organisms TROPHIC LEVELS Primary Producer All autotrophs in an ecosystem Consumer All heterotrophs in an ecosystem Herbivore Heterotrophs that feed directly on the primary producers Primary Carnivore Heterotrophs that feed directly on the herbivores Secondary Carnivore Heterotrophs that feed directly on primary carnivores Detritivore Organisms that feed on detritus (dead organic matter) Food Chain – A sequence of progressive trophic levels ChadsPrep.com 62  PRODUCTIVITY The rate at which the organisms in a trophic level create Productivity organic matter Primary Productivity Productivity of primary producers Gross Primary Raw rate at which primary producers create organic Productivity (GPP) matter Net Primary = (GPP - respiration rate) of the primary producers Productivity (NPP) Secondary Productivity Productivity of a heterotrophic level Trophic-Level Interactions Trophic Cascade – The process by which effects on an upper trophic level affect two or more lower trophic levels. Top-Down Effects – Effects on an upper trophic level that flow down to affect lower trophic levels. Bottom-Up Effects – Effects on a lower trophic level that flow up to affect higher trophic levels. Species richness (i.e. biodiversity) of communities results in greater stability. Habitat heterogeneity results in greater species richness. ChadsPrep.com 63 Biosphere PERCENTAGE OF EARTH’S SURFACE Terrestrial Freshwater Marine Biomes Habitats Habitats 27% 2% 71% TERRESTRIAL BIOMES Climate Characteristics High Temperature Highest Biodiversity Tropical Rainforest High Precipitation Ex. Amazon Rainforest Savanna Warm Ex. Serengeti (Tropical/Subtropical Moderate Precipitation Grassland) (Often seasonal) Low Precipitation Sparse Vegetation (Unpredictable) Water Conservation Desert Cacti Ex. Mojave, Antarctic Temperate Climate Rich Soil Temperate Grassland Productive for Agriculture (Prairies) Ex. Interior of North America Warm summers/ Deciduous trees drop leaves in Temperate Deciduous Cold winters winter Forest Moderate Precipitation Ex. Eastern North America Temperate Climates Pine, spruces, redwoods Temperate Evergreen High Precipitation Northwest United States Forest Along Coastlines Harsh winters Northern forests Limited Precipitation Coniferous trees Taiga Elk, moose, deer, wolves, beers Ex. Much of Alaska/Canada Low Precipitation Far north Permafrost Few trees Tundra Reindeer, wolves, foxes Covers 20% of land Northern Alaska/Canada ChadsPrep.com 64 Freshwater Habitats Lakes, ponds, rivers, streams Littoral Zone shallows near the edges Zone near the surface where there is enough Photic Zone sunlight for primary producers Zone beneath the Photic zone that does not Aphotic Zone receive sufficient light for primary producers Thermal Stratification – The formation of distinct layers in a body of water with a warmer, less dense layer at the surface and much colder, more dense layers below. Oligotrophic Eutrophic Nutrient Content Low High Algae Content Low High O2 Concentration High Low Sunlight Penetrance High Low Marine Habitats 1. Open Oceans – Waters far from land but fairly near the surface. Low in nutrients and low primary productivity High sunlight near the surface (photic zone) but zero at a depth of 200m and below 2. Continental Shelves – Relatively shallow areas near coastlines Source of much of the marine food and mineral resources Estuary – Shelf ecosystem along the coast where fresh water from streams/rivers mixes with ocean water resulting in intermediate ‘brackish’ water. Includes intertidal habitats. Banks – local shallow areas important for fishing Coral Reefs – Unique shelf ecosystems in tropical/subtropical latitudes having a variety of coral and reef fish populations 3. Upwelling Regions – localized regions where deep water is continually drawn to the surface through the action of wind or other forces. This brings nutrients to the surface resulting in the highest primary productivity in the ocean. 4. Deep Sea – cold, dark, and under high pressure Food is the result of photosynthesis at the surface Hydrothermal Vent Communities – Occur where tectonic plates are moving apart Primary producers are chemoautotrophs that oxidize hydrogen sulfide for energy. ChadsPrep.com 65