Ecology and Evolution Review

Ecology and Evolution Review

4.1 Interactions within Ecosystems

• Biotic vs. Abiotic Factors:

  • Biotic factors are the living components of an ecosystem, such as plants, animals, and microorganisms.

  • Abiotic factors are the non-living components, including sunlight, temperature, water, and soil.

• Habitat vs. Niche:

  • A habitat is the physical environment where an organism lives.

  • A niche is the role an organism plays in its environment, including its interactions with biotic and abiotic factors.

4.2 Terrestrial and Aquatic Ecosystems

• Biomes:

  • Large geographic areas characterized by specific climate conditions, animal populations, and plant adaptations.

• Lake Zones:

  • Littoral zone: The shallow zone near the shore where sunlight penetrates to the bottom.

  • Limnetic zone: The open water zone where sunlight penetrates, supporting plankton and fish.

  • Profundal zone: The deep-water zone where sunlight does not penetrate; it's cold and dark.

  • Benthic zone: The bottom of the lake, inhabited by decomposers and bottom-dwelling organisms.

4.3 Factors Affecting Ecosystems

• Soil Layers:

  • O Horizon: The uppermost layer, rich in organic material (humus).

  • A Horizon: Topsoil, a mixture of organic material and minerals.

  • B Horizon: Subsoil, rich in minerals from above.

  • C Horizon: Parent material, partially weathered rock.

  • R Horizon: Bedrock.

• Seasonal Variations in Lakes:

  • Turnover: Seasonal mixing of lake waters due to changes in temperature and density.

  • Stratification: Formation of distinct layers (epilimnion, thermocline, hypolimnion) during summer.

4.4 Limits of Populations and Communities in Ecosystems

• Density-Dependent Factors:

  • Factors that affect population growth based on population density, such as competition, predation, parasitism, and disease. The effect intensifies as population density increases.

• Density-Independent Factors:

  • Factors that affect population growth regardless of population density, such as natural disasters, weather, and climate.

4.5 Changes in Ecosystems

• Forestry Practices:

  • Clear cutting: Removal of all trees in an area.

  • Slash and burn: Cutting and burning vegetation to clear land.

  • Selective cutting: Removal of specific trees while leaving others intact.

    • Clear cutting and slash and burn are bad compared to the alternative.

• Dissolved Oxygen:

  • The amount of oxygen gas dissolved in water, essential for aquatic life.

• Biological Oxygen Demand (BOD):

  • The amount of oxygen required by microorganisms to decompose organic matter in water. High BOD indicates high levels of pollution.

5.1 Classification of Organisms

• Naming Systems:

  • Binomial nomenclature: A two-part naming system using genus and species (e.g., Homo sapiens).

• Dichotomous Key:

  • A tool used to identify organisms based on a series of paired choices.

  • Each step in the key presents two mutually exclusive statements, leading the user to the correct identification.

5.2 Evidence of a Changing Earth

• Fossil Evidence:

  • Fossils provide a record of past life and show how organisms have changed over time.

    • The fossil record is incomplete, but can show the development of current existing organisms.

• Biogeography:

  • The geographic distribution of species. Similar species are often found in geographically close areas.

    • Marsupials in Australia and placental mammals elsewhere.

5.3 Evidence of Evolution from Biology

• Homologous vs. Analogous Structures:

  • Homologous structures: Structures with similar underlying anatomy due to common ancestry, but different functions (e.g., the forelimbs of mammals).

  • Analogous structures: Structures with similar functions but different underlying anatomy and evolutionary origins (e.g., the wings of insects and birds).

• Biochemistry/Molecular Biology:

  • Similarities in DNA, RNA, and protein sequences among different species provide evidence of common ancestry.

5.4 The Making of a Theory – Accounting for Evolution

• Darwin vs. Lamarck:

  • Lamarck: Inheritance of acquired characteristics (traits acquired during an organism's lifetime are passed on to offspring).

  • Darwin: Natural selection (individuals with advantageous traits are more likely to survive and reproduce).

• Natural Selection:

  • The process by which organisms with traits that better enable them to adapt to their environment tend to survive and reproduce in greater numbers than others of their species.

5.5 Sources of Inherited Variation

• Variation:

  • Differences in traits among individuals within a population.

• Mutation:

  • Changes in DNA sequence that can lead to new traits.

  • Source of all genetic variation.

5.6 Speciation and Evolution

• Allopatric Speciation:

  • The formation of new species due to geographic isolation.

  • Populations are split geographically and can develop separate traits and speciation.

• Sympatric Speciation:

  • The formation of new species without geographic isolation.

  • Can happen as mutation or change in behavior leads to reproductive isolation in population.

• Punctuated Equilibrium vs. Gradualism:

  • Punctuated equilibrium: Long periods of stasis (no change) followed by short periods of rapid change.

  • Gradualism: Slow, continuous change over long periods.

• Divergent vs. Convergent Evolution:

  • Divergent evolution: When closely related species evolve in different directions because of different environmental pressures.

  • Convergent evolution: When distantly related species evolve similar traits because of similar environmental pressures; this can result in analogous structures.