AP Bio Unit 8: Ecology

Behavior

• Behavior - an organism’s response to the environment

  • Can be:

  • instinctual (inborn)

  • learned

  • social

• Types of Social Behavior

  • agnostic behavior

  • dominance hierarchies

  • territoriality

  • altruistic behavior

• Tropism - plant specific behavior

  • phototropism

  • gravitropism

  • thigmotropism

Ecology

• Seven major biomes make up the biosphere, each biosphere contains ecosystems

  • tundra

  • taiga

  • temperate deciduous forest

  • grasslands

  • deserts

  • tropical rainforest

• Within an ecosystem are communities

  • Consist of organisms fulfilling one of the three main roles:

    • Producers/autotrophs

      • Convert light energy to chemical energy via photosynthesis

    • Consumers/heterotrophs

      • Get energy from things they consume

      • Digestion of carbohydrates produced carbon, hydrogen, and oxygen, which are then used to make organic substances

    • Decomposers form fossil fuels from the detritus of other organisms in the ecosystem

• 10% rule - only 10% of the energy consumed from one level will be retained by the higher level that consumed it

  • Other energy is spent to perform daily activities

• The smallest unit of ecology is the population

  • The growth of a population can be found with the equation (r) = (births-deaths) / N

• The carrying capacity is the maximum number of individuals that can be supported by a habitat

  • Most populations do not reach carrying capacity due to factors such as population density (density-independent factors and density-dependent factors)

• Exponential growth (J shaped curve) occurs when a population is in an ideal environment

• Logistic growth (S shaped curve) of a population occurs when there are limited resources in an environment

• Organisms are generally either r-strategists or k-strategists

  • The r-strategists ensure their survival by producing lots of offspring

  • The k-strategists (usually large animals) produce few offspring but have longer life spans and less competition from other organisms for resources

• Succession describes the way in which ecosystems recover after a disturbance in terms of pioneers, sere, community, and secondary succession

• Human impact on the planet includes the following issues:

  • greenhouse effect

  • ozone depletion

  • acid rain

  • desertification

  • deforestation

  • pollution

  • reduction in biodiversity

  • introduction and spread of disease

Key Terms

• Endotherms – Organisms that regulate their body temperature internally, typically through metabolic processes (e.g., mammals, birds).

• Ectotherms – Organisms whose body temperature is influenced by external environmental conditions (e.g., reptiles, amphibians).

• Behavior – The actions or reactions of an organism in response to external or internal stimuli.

• Instinct – Inborn, unlearned behaviors that are performed correctly without prior experience.

• Learning – A process in which an organism modifies its behavior based on experience.

• Imprinting – A type of learning occurring at a specific stage in life, where an animal forms strong associations (e.g., ducklings following their mother).

• Critical Period – A limited time frame during which an organism must be exposed to certain stimuli for proper development.

• Habituation – A type of learning in which an organism decreases or ceases its responses to a repetitive stimulus.

• Circadian Rhythms – Biological processes that follow a 24-hour cycle, such as sleep-wake cycles in humans.

• Pheromones – Chemical signals released by animals that affect the behavior or physiology of others in the species.

• Agonistic Behavior – Social behavior related to fighting, including threats, aggression, and submission.

• Dominance Hierarchy – A ranking system within a group that determines access to resources and mates (e.g., pecking order in chickens).

• Territoriality – The defense of a specific area against intruders, often seen in animals like birds and mammals.

• Altruistic Behavior – Actions that benefit another organism at a cost to oneself, often seen in social animals (e.g., bees sacrificing for the hive).

• Symbiotic Relationship – A close and long-term interaction between two species.

  • Mutualism – Both species benefit (e.g., bees and flowers).

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

  • Parasitism – One species benefits while harming the other (e.g., tapeworms in humans).

• Photoperiodism – A plant’s response to the length of day and night, influencing flowering and growth.

• Tropism – A plant’s growth response to external stimuli.

  • Phototropism – Growth toward or away from light.

  • Gravitropism – Growth in response to gravity (roots grow downward, stems grow upward).

  • Thigmotropism – Growth in response to touch (e.g., vines wrapping around structures).

• Auxins – Plant hormones that promote cell elongation and are involved in phototropism.

• Gibberellins – Plant hormones that stimulate growth, germination, and flowering.

• Cytokinins – Plant hormones that promote cell division and delay aging in leaves.

• Ethylenes – Plant hormones that regulate fruit ripening and response to stress.

• Abscisic Acid – A plant hormone that inhibits growth and promotes seed dormancy.

• Ecology – The study of interactions between organisms and their environment.

• Biotic Factors – Living components of an ecosystem (e.g., plants, animals, bacteria).

• Abiotic Factors – Non-living environmental factors (e.g., temperature, water, sunlight).

• Carbon Cycle – The movement of carbon through the atmosphere, biosphere, and geosphere, including processes like photosynthesis and respiration.

• Niche – The role or function of an organism in its ecosystem, including resource use and interactions.

• Food Chain – A linear sequence showing energy flow from producers to consumers.

• Primary Productivity – The rate at which producers convert solar energy into chemical energy (biomass).

• Biomass – The total mass of living organisms in a given area.

• Keystone Species – A species that has a disproportionately large impact on its ecosystem (e.g., wolves in Yellowstone).

• 10% Rule – Only about 10% of energy is transferred between trophic levels in a food chain; the rest is lost as heat.

• Ecological Pyramid – A graphical representation of biomass, energy, or numbers of organisms at each trophic level.

• Bioaccumulation – The buildup of toxic substances within an organism over time.

• Biomagnification – The increase in concentration of toxins as they move up the food chain.

• Simpson’s Diversity Index – A measure of biodiversity within an ecosystem, considering species richness and evenness.

• Carrying Capacity – The maximum population size an environment can sustain over time.

• Population Density – The number of individuals per unit area or volume.

• Density-Independent Factors – Environmental factors affecting population size regardless of density (e.g., natural disasters).

• Density-Dependent Factors – Factors whose effects depend on population density (e.g., competition, disease).

• r-Strategists – Species that reproduce rapidly, have many offspring, and provide little parental care (e.g., insects).

• K-Strategists – Species that reproduce slowly, have fewer offspring, and invest in parental care (e.g., elephants).

• Ecological Succession – The gradual process by which ecosystems change over time.

  • Primary Succession – Occurs in areas where no life previously existed (e.g., volcanic rock).

  • Secondary Succession – Occurs after a disturbance but soil remains (e.g., after a wildfire).

• Pioneer Organisms – The first species to colonize a barren area (e.g., lichens in primary succession).

• Sere – A stage in the ecological succession process.

• Climax Community – A stable, mature ecosystem that has reached equilibrium.

• Greenhouse Effect – The trapping of heat in Earth’s atmosphere by greenhouse gases (e.g., CO₂, methane).

• Ozone Depletion – The thinning of the ozone layer due to chemicals like CFCs, increasing UV radiation exposure.

• Acid Rain – Precipitation with high acidity due to atmospheric pollution (e.g., sulfur and nitrogen compounds).

• Desertification – The degradation of land into desert, often due to deforestation, drought, or poor agricultural practices.