better ap bio ecology unit 8

Characteristics of Life

• Made of Cells: All living things are composed of one or more cells.

• Reproduction: Must be able to produce offspring (sexually or asexually).

• Metabolism: Ability to convert energy for cellular functions.

• Excretion: Removal of waste products.

• Growth and Development: Capacity to grow and change over time.

• Response to Stimuli: React to changes in the environment.

• Environmental Adaptation: Make physiological or behavioral changes in response to surroundings.

Responses to the Environment

• Organisms respond to their environment via physiological changes or behavioral adaptations.

• Examples:

  • Plants are phototropic (grow toward light sources).

  • Flowers display specific colors to attract pollinators like bees.

  • Animals release hormones for "fight or flight" in response to threats.

Ways Organisms Respond to the Environment:

• Change in physical appearance (e.g., color changes for camouflage or signaling).

• Alter taste or chemical composition for protection (e.g., toxic plants).

• Use signals for:

  • Territory marking.

  • Establishing dominance.

  • Locating food.

  • Reproductive success.

Natural Selection and Behavior

• Behaviors that increase fitness (ability to survive and reproduce) are favored by natural selection.

  • Example: Birds flying in flocks or schools of fish reduce predation risk and increase reproductive success.

Metabolism

• Organisms need energy intake and produce cellular output.

• Energy intake must exceed energy use for growth; if not, it leads to energy loss, stunted growth, and eventual death.

Endotherms vs. Ectotherms

• Endotherms:

  • Use metabolic energy to maintain body temperature.

  • Require more energy than ectotherms.

• Ectotherms:

  • Regulate body temperature behaviorally (e.g., basking in sunlight).

Metabolic Rates and Size

• Smaller animals have higher metabolic rates than larger animals.

Energy Acquisition

• Autotrophs: Capture energy from physical or chemical sources.

  • Photoautotrophs: Use sunlight (e.g., plants, algae).

  • Chemoautotrophs: Use inorganic molecules (e.g., some microorganisms).

• Heterotrophs: Obtain energy from organic molecules produced by other organisms (e.g., carbohydrates, lipids, proteins).

Energy and Matter Exchange

• Matter cycles continuously in ecosystems (e.g., water, carbon, nitrogen).

• Energy flows through ecosystems (sunlight to producers to consumers).

Trophic Levels

• Primary Producers: Autotrophs like plants capture energy from the sun.

• Primary Consumers: Herbivores that consume producers.

• Secondary Consumers: Carnivores that eat herbivores.

• Tertiary Consumers: Top-level predators.

• Apex Predators: Predators at the top of the food chain.

• Only 10% of energy passes to the next trophic level; the rest is lost as heat.

Energy Disruptions in Ecosystems

• Reduced sunlight leads to energy loss for all trophic levels.

• Fewer producers reduce energy for consumers, disrupting ecosystems.

Population Ecology

Population Growth

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

• Growth Factors:

  • If birth rate > death rate: Population increases.

  • If birth rate < death rate: Population decreases.

  • If birth rate = death rate: Population remains steady.

Factors Limiting Growth

• Density-Dependent Factors:

  • Competition, predation, disease, waste accumulation.

  • Territoriality can also limit population size.

• Density-Independent Factors:

  • Weather events, natural disasters, human activities.

Population Dynamics

• Growth rate equation: dN/dt = B – D (birth rate minus death rate).

• Exponential Growth:

  • No limiting factors.

  • Population grows by a constant proportion (J-shaped curve).

  • Equation: dN/dt = r_max N.

• Logistic Growth:

  • Growth slows as population approaches carrying capacity (S-shaped curve).

  • Equation: dN/dt = rN(K – N)/K.

Carrying Capacity (K):

• Maximum population size an environment can sustain.

• Populations often stabilize near carrying capacity due to resource limitations.

Community Ecology

Community Structure

• Defined by species composition and diversity.

• Diversity measured using Simpson's Diversity Index:

  • Equation: 1 – ∑ (n/N)^2, where "n" is individuals of a species, and "N" is total individuals.

  • Accounts for species richness and relative abundance.

Interspecific Interactions

• Competition: Species compete for limited resources (e.g., food, space).

  • Competitive Exclusion: One species outcompetes the other.

  • Niche Partitioning: Coexistence by using different resources or areas (e.g., anoles in distinct habitats).

• Exploitation: One species benefits at another's expense.

  • Predation: Predator-prey dynamics.

  • Herbivory: Animals feed on plants/algae.

  • Parasitism: Parasites harm their hosts.

• Mutualism: Both species benefit (e.g., clownfish and anemones).

• Commensalism: One species benefits; the other is unaffected (e.g., barnacles on whales).

Biodiversity

• Variety of living organisms in ecosystems.

• Biodiverse ecosystems are more resilient to environmental changes.

• Loss of biodiversity reduces ecosystem stability and homeostasis.

Ecosystem Function

• Autotrophs convert sunlight into usable energy for heterotrophs.

• Ecosystems collapse without primary producers.

Key Species

• Dominant Species: Most abundant species in a community.

• Keystone Species: Species with a disproportionate impact on ecosystem function. Loss can lead to ecosystem collapse.

Natural Selection and Extinction

Adaptation and Fitness

• Natural selection allows species to adapt to their environments.

• Random mutations drive genetic variation; selection is non-random.

Extinction Causes (HIPCO):

1. Habitat Loss: Urbanization, deforestation.

2. Invasive Species: Outcompete natives and disrupt ecosystems.

3. Pollution: Degrades habitats and harms species.

4. Climate Change: Alters weather, temperature, and ecosystems.

5. Overexploitation: Overfishing, hunting, and unsustainable practices.

Impact of Human Activity

• Habitat loss and fragmentation reduce genetic diversity and promote inbreeding.

• Urbanization causes "extinction vortices" where one disruption leads to others.

• Invasive species thrive without natural predators, altering ecosystems.

• Geological and meteorological events can disrupt ecosystems (e.g., continental drift).

Summary

• Living organisms share common traits like cellular structure, energy use, and response to stimuli.

• Ecosystems rely on energy flow and nutrient cycling, and changes can disrupt trophic levels.

• Population and community dynamics depend on growth factors, interspecific interactions, and diversity.

• Biodiversity ensures resilience; conservation efforts are vital for ecosystem stability.

Key Formulas:

• Growth rate: dN/dt = B – D.

• Exponential growth: dN/dt = r_max N.

• Logistic growth: dN/dt = rN(K – N)/K.

• Simpson’s Diversity Index: 1 – ∑ (n/N)^2.