Ecology & Evolution Study Guide

1. Energy Flow Through Ecosystems

• Photoautotrophs: Organisms that use sunlight to produce food through photosynthesis (e.g., plants, algae).

• Chemoautotrophs: Organisms that obtain energy by oxidizing inorganic substances (e.g., certain bacteria).

• Heterotroph: Organism that consumes other organisms for energy.

• Endotherm: Organism that regulates its body temperature internally (e.g., birds, mammals).

• Endotherm Temperature Regulation: Through metabolic heat production, shivering, sweating, panting.

• Ectotherm: Organism that relies on external environment for body heat (e.g., reptiles, amphibians).

• Ectotherm Temperature Regulation: Behavioral adaptations like basking, burrowing.

• More Food in Cold?: Endotherms require more food in cooler environments to maintain body temperature.

• Temperature & Oxygen in Endotherms: Lower temperatures increase oxygen consumption due to higher metabolic rate.

• Metabolic Rate vs. Body Size: Smaller organisms have higher metabolic rate per unit body mass.

• Energy Availability & Population Size: More energy = larger populations; less energy = smaller populations.

• Sunlight Decrease: Fewer producers; smaller and fewer higher trophic levels.

• Sunlight Increase: More producers; larger and more numerous higher trophic levels.

• Producer Decrease: Collapse or shrinkage of higher trophic levels.

• Producer Increase: Expansion of higher trophic levels.

2. Animal Behavior & Environmental Response

• Behavioral Responses: Organisms adjust behavior based on internal/external changes (e.g., migration, hibernation).

• Differential Reproductive Success: Some individuals reproduce more due to favorable traits.

• Communication & Reproduction: Signals (e.g., mating calls) can enhance mating success.

• Types of Signals:

  • Visual (open habitats)

  • Auditory (dense forests)

  • Tactile (close contact)

  • Chemical (nocturnal or aquatic)

  • Electrical (aquatic)

• Function of Communication: Coordination, mating, territory defense, warning.

• Innate Behavior: Genetically programmed, not learned (e.g., reflexes).

• Learned Behavior: Acquired through experience (e.g., imprinting, conditioning).

• Favored Behaviors: Those increasing survival and reproduction.

• Cooperative Behavior: Group behaviors (e.g., hunting, defense) that increase fitness.

• Altruism: Helping others at a cost; often benefits relatives (kin selection).

• Altruism & Fitness: Increases survival and reproduction of relatives, preserving shared genes.

3. Population Dynamics

• Population: Group of individuals of same species in an area.

• Population Interactions: Competition, predation, mutualism.

• Population & Environment: Affected by resources, space, climate.

• Population Growth:

  • Exponential: Unlimited resources, rapid growth.

  • Logistic: Growth slows as resources become limited.

• Carrying Capacity: Max population an environment can support.

• Density-Dependent Factors: Affected by population size (e.g., disease, food).

• Density-Independent Factors: Unrelated to population size (e.g., weather, natural disasters).

4. Community Interactions

• Positive Interactions: Mutualism, commensalism.

• Negative Interactions: Competition, predation, parasitism.

• Trophic Cascades: Ripple effects through trophic levels due to changes at the top or bottom.

• Niche Partitioning: Species divide resources to reduce competition.

• Interaction Types: Mutualism, commensalism, predation, parasitism, competition.

5. Species Diversity & Richness

• Keystone Species: A species with a disproportionately large effect on its environment.

• Abiotic Factors: Non-living (e.g., temperature, light).

• Biotic Factors: Living (e.g., predation, disease).

• Simpson's Index: Measures biodiversity; considers richness and evenness.

Evolution

1. Mechanisms of Evolution

• Phenotype: Observable traits.

• Genotype: Genetic makeup.

• Phenotypic Variation: Crucial for natural selection and adaptability.

• Fitness: Ability to survive and reproduce.

• Mutation Types: Point, insertion, deletion, chromosomal.

• Mechanisms: Mutation, gene flow, genetic drift, natural selection.

• Natural Selection: Acts on variation; pressures include predators, climate.

• Directional Selection: Favors one extreme trait; occurs with environmental change.

• Artificial Selection: Human-driven breeding for traits.

2. Evidence of Evolution

• Evidence Types: Fossils, anatomy, molecular, embryology, biogeography.

• Homologous Structures: Similar structure, different function; shared ancestry.

• Analogous Structures: Different structure, same function; no common ancestry.

• Selection Pressure & Adaptation: Similar environments lead to similar adaptations.

• Convergent Evolution: Unrelated species evolve similar traits.

• Divergent Evolution: Related species evolve different traits.

3. Population Genetics

• Allele: Variant of a gene.

• Allele Frequency: Proportion of an allele in a population.

• Hardy-Weinberg Conditions: No mutation, migration, selection; random mating; large population.

• Equations:

  • p = dominant allele frequency

  • q = recessive allele frequency

  • p^2 = homozygous dominant

  • q^2 = homozygous recessive

  • 2pq = heterozygous

• Population Evolution: Detected when allele frequencies change.

4. Phylogenetics & Cladograms

• Cladogram: Diagram showing evolutionary relationships.

• Tools: Morphological data, molecular data (best for accuracy).

• Shared Derived Characters: Traits unique to a clade.

• Common Ancestor: Shared origin point; found at branch points.

• Branch Point: Represents divergence from common ancestor.

5. Speciation

• Species: Group that can interbreed and produce fertile offspring.

• Reproductive Isolation: Prevents interbreeding.

• Allopatric Speciation: Physical barrier separates populations.

• Sympatric Speciation: Occurs without physical separation.

• Isolation Types:

  • Prezygotic: Temporal, behavioral, mechanical, gametic.

  • Postzygotic: Hybrid sterility, inviability.

• Hybrids: Offspring of two species; often sterile or less fit.

• Punctuated Equilibrium: Rapid changes with stability in between.

• Gradualism: Slow, steady evolutionary change.

6. Origin of Species

• Extinction Causes: Environmental change, loss of resources, competition.

• Miller-Urey Experiment: Simulated early Earth; produced organic molecules.

• RNA World Hypothesis: RNA was first genetic material; self-replicating and catalytic.