Ecosystems: Species, Population & Natural Selection

• Study notes based on the provided questions.

Ecosystems

• Species: A group of similar organisms that can interbreed and produce fertile offspring.
• Population: A group of individuals of the same species living in the same area.
• Community: All the different populations of species living in the same area and interacting with each other.
• Ecosystem: A community of living organisms (biotic factors) interacting with each other and their physical environment (abiotic factors).
• Natural Selection: The process where organisms with favorable traits are more likely to survive and reproduce, passing those traits to the next generation. Natural selection drives evolutionary change.
• Ecological Niche: The role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces.
• Components of a niche: range, prey, predators, habitat, and behaviors.
• Fundamental Niche: The entire set of conditions under which an organism can survive and reproduce.
• Realized Niche: The actual set of conditions under which an organism exists, after accounting for limiting factors like competition.
• Limiting factors influence the realized niche by restricting where an organism can live and reproduce.
• Resource Partitioning: The division of resources among coexisting species, where different species utilize different parts of the habitat, or different resources, to reduce competition.
• Different habitats within an ecosystem support different species due to resource partitioning.
• Competitive Exclusion Principle: Two species competing for the same limited resource cannot coexist at constant population values; one will eventually outcompete and eliminate the other.
• When two species overlap, one will be driven to extinction or forced to evolve a different niche.
• Having different niches provides a biological advantage as it reduces competition for resources.
• Terrestrial Ecosystem Zones: Include forests, grasslands, deserts, etc., each with distinct temperature, moisture, and light conditions.
• Aquatic Ecosystem Zones: Include freshwater (lakes, rivers) and marine (oceans, coral reefs) zones, each with varying salinity, depth, and light penetration.
• A species may only survive in certain zones due to its specific adaptations to those conditions.
• The forest floor has bugs under decomposing leaves (less sun, less oxygen), while the tree line has more sun and oxygen.
• Abiotic factors in Terrestrial Ecosystems: temperature, rainfall, sunlight, and soil composition.
• Abiotic factors in Aquatic Ecosystems: salinity, water temperature, light penetration, and dissolved oxygen.
• Common abiotic factors: temperature and availability of water.
• Specific to terrestrial: soil type.
• Specific to aquatic: salinity.
• Biotic Factors: living components of an ecosystem.
• Density-Dependent Factors: Factors that affect a population based on its size.
• Competition
• Disease
• Predation
• Density-Independent Factors: Factors that affect a population regardless of its size.
• Natural disasters
• Temperature
• Habitat destruction
• Binomial Nomenclature: A two-term naming system used to classify living organisms.
• Binomial nomenclature reflects organism's evolutionary relationships.
• Rules for Writing: Genus name is capitalized, species name is lowercase, and the entire name is italicized or underlined.
• Levels of Classification:
• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
• Six Kingdoms:
• Animals
• Plants
• Fungi
• Protists
• Archaebacteria
• Eubacteria
• Animalia: eukaryotic, multicellular, heterotrophic
• Plantae: eukaryotic, multicellular, autotrophic
• Fungi: eukaryotic, multicellular, heterotrophic
• Protista: eukaryotic, mostly unicellular, can be autotrophic or heterotrophic
• Archaebacteria: prokaryotic, unicellular, can live in extreme environments
• Eubacteria: prokaryotic, unicellular, diverse metabolic capabilities
• Holozoic Nutrition: Animals ingest and digest their food internally.
• Saprotrophic Nutrition: Organisms feed on dead or decaying organic matter.
• Fungi and some bacteria demonstrate saprotrophic nutrition.
• Facultative Anaerobe: Can grow in the presence or absence of oxygen.
• Obligate Aerobe: Requires oxygen for growth.
• Obligate Anaerobe: Cannot survive in the presence of oxygen.

Evolution

• Variation: Differences in traits within a population which is important because it allows for adaptation to changing environments.
• Sources of variation: mutation and sexual reproduction.
• Adaptation: a trait that increases an organism's ability to survive and reproduce in its environment.
• An adaptation's helpfulness depends on the environment.
• Lamarck's Theory of Acquired Characteristics: Traits acquired during an organism's lifetime are passed on to its offspring.
• Darwin's Natural Selection:
• Overproduction: organisms produce more offspring than can survive.
• Variation: individuals within a population vary in their traits.
• Selective pressure: the environment favors certain traits.
• Heritability: favorable traits are passed on to the next generation.
• Natural Selection: The process by which organisms with favorable traits are more likely to survive and reproduce.
• Selective Pressure: An environmental factor that affects an organism's ability to survive and reproduce, leading to natural selection.
• Evolutionary Fitness: An organism's ability to survive and reproduce in its environment.
• Evolutionary fitness is related to natural selection because individuals with higher fitness are more likely to pass on their genes.
• Fossil Record: Fossils show the change of life forms over time, and demonstrates the transition from ancestral forms to modern species.
• Analogous Structures: Structures that have similar functions but different evolutionary origins.
• Vestigial Structures: Structures that have lost their original function over time, providing evidence of evolutionary history.
• Homologous Structures: Structures that have a common evolutionary origin but may have different functions.
• Biogeography: The study of the geographic distribution of species, which shows how species evolve in different regions based on their environments.
• DNA Similarities: Similarities in DNA sequences suggest common ancestry; closely related species have more similar DNA.
• Artificial Selection: Humans selectively breed organisms for desired traits.
• Convergent Evolution: Unrelated species evolve similar traits because they adapt to similar environments.
• Example: wings in birds and insects.
• Divergent Evolution: Related species evolve different traits because they adapt to different environments.
• Example: Darwin's finches.
• Adaptive Radiation: A rapid diversification of a single ancestral lineage into multiple species, each adapted to a different ecological niche.
• Adaptive radiation applies to divergent evolution, as species evolve different traits to occupy various niches.
• Descent with Modification: The concept that species change over time, with new species arising from ancestral forms.
• Transitional Fossil: A fossil that exhibits traits of both ancestral and derived forms, providing evidence of evolutionary transitions.
• Allopatric Speciation: Speciation that occurs when populations are geographically isolated from each other.
• Two Rates of Speciation:
• Gradualism: Slow, gradual changes over long periods of time.
• Punctuated equilibrium: long periods of stasis interrupted by brief periods of rapid change.