AP Biology Unit 8 Definitions

Ecology and Behavior

Behavioral Ecology

The study of how organisms interact with their environment through behavior.

Ethology

The study of animal behavior mechanisms and the evolutionary significance of behavior.

Behavior

The observable actions of an organism in response to its environment, usually carried out by the muscular or hormonal system.

Proximate Causes

The stimuli and mechanisms triggering the behavior.

Ultimate Causes

The evolutionary explanations for why the behavior exists.

Nature vs. Nurture

Nature is the influence of inherited genetic programming.

Nurture is the influence of environmental factors.

Innate Behaviors

Behavior that is genetically controlled and does not require learning. It is often crucial for survival and found in nearly all organisms of a species.

Fixed Action Patterns (FAPs)

an innate behavior

A sequence of unchangeable, instinctive behaviors that is triggered by a sign stimulus, an external cue.

Once started, it is usually carried to completion.

Ex. A goose retrieving an egg back to its nest.

Behavioral Rhythms

Circadian, Circannual, Lunar

Circadian Rhythm: a daily cycle of rest and activity

Circannual Rhythm (changing seasons): mainly affects migration and reproduction, with common seasonal cues like daylight and darkness

Lunar Cycles: affect tidal movements

Migration

an innate behavior

The seasonal movement of organisms, usually triggered by environmental cues like temperature and daylight.

Signals and Communication

an innate behavior

Nocturnal vs Diurnal

Signals are behaviors that cause a change in another animal’s behavior.

Communication is the transmission and reception of signals.

Organisms use different signals to communicate:

1. Visual (warning coloration in frogs)

2. Auditory (bird songs, whale calls)

3. Tactile (grooming in primates)

4. Electrical (electric fish communication)

5. Chemical (pheromones used by ants and bees)

Nocturnal animals depend on olfactory and auditory communication while Diurnal animals use visual and auditory communication.

Kinesis

an innate behavior

A non-direction response to a stimulus.

Ex. Increased activity in pill bugs in humid environments

Taxis

an innate behavior

Phototaxis, Chemotaxis, Geotaxis

A directed movement toward or away from a stimulus. Positive taxis is toward the stimulus and negative taxis is away from the stimulus.

Phototaxis: in response to light

Chemotaxis: in response to chemicals

Geotaxis: in response to gravity

Learned Behaviors

Behaviors that develop through experience and environmental interaction.

Imprinting

a learned behavior

Learning that occurs during a critical period and is often irreversible.

Spatial Learning

a learned behavior

Recognizing landmarks to navigate the environment.

Cognitive Maps

a learned behavior

A mental representation of the surroundings for navigation.

Associative Learning

a learned behavior

Classical Conditioning and Operant Conditioning

Associating one stimulus with another.

Classical Conditioning: an arbitrary stimulus is associated with a reward or punishment

Operant Conditioning (trial-and-error learning): an animal associating one of its behaviors with a reward or punishment

Cognition and Problem Solving

Cognition: a process of knowing that may include awareness, reasoning, recollection and judgement

Problem Solving: the process of devising a strategy to overcome an obstacle

Social Learning

a learned behavior

Culture

Learning through observing and imitating others.

Culture is formed by social learning. It is a system of information transfer through observation and teaching that influences the behavior and fitness of individuals in a population.

Foraging Behavior

according to the Optimal Foraging Model

Efficient food-seeking strategies that maximize energy intake while minimizing risks and energy loss.

Sexual Dimorphism

Differences in the appearances of male and female organisms in the same species resulting from sexual selection.

Intersexual Selection

a type of sexual selection

Female Choice and Mate-Choice Copying

Members of one sex choose mates based on certain traits.

Female Choice: females drive sexual selection by choosing mates with specific behaviors and anatomical features that often correlate with health and vitality

Mate-Choice Copying: a behavior where individuals copy the mate choice of others

Intrasexual Selection

a type of sexual selection

Male Competition

Competition between members of the same sex for mates.

Male Competition: Reduces variation in males. This may involve agonistic behavior, often a ritualized contest that determines which competitor gains access to a resource.

Mating Behavior

Seeking or attracting mates, choosing mates, competing for mates, and caring for offspring.

Monogamy Mating Systems

A mating system where one sex takes one partner of the other sex.

Usually low sexual dimorphism (male and females look the same)

Polygamy Mating Systems

Polygyny and Polyandry

A mating system where one sex takes multiple partners of the other sex.

Usually high sexual dimorphism.

Polygyny: one male mates with many females, and the males are usually more showy and larger than the females

Polyandry: one female mates with many males, and the females are usually more showy than the males

Paternal Certainty

Internal and External Fertilization

Paternal certainty affects parental care and mating behavior.

Internal Fertilization: Paternal certainty is low because mating and birth are separated over time. Parental care is more likely to be by females.

External Fertilization: Paternal certainty is high because egg laying and mating occur together. Parental care is equally likely to be by males as by females.

Game Theory

Frequency-Dependent Selection

Evaluates alternative strategies where the outcome depends on each individual’s strategy and the strategy of other individuals.

Like rock-paper-scissors, each strategy will outcompete one strategy but be outcompeted by the other strategy. The success of each strategy depends on the frequency of all of the strategies, driving frequency-dependent selection.

Inclusive Fitness

The total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring.

Altruism

a cooperative behavior

Cooperative behavior that benefits other organisms at a personal cost.

Reciprocal Altruism

an altruistic behavior

Altruistism towards unrelated individuals that can be adaptive if the aided individual returns the favor in the future. This is limited to species with stable social groups where individuals meet repeatedly and cheaters who don’t reciprocate are “punished”.

Kin Selection

an altruistic behavior

Altruistic behavior that benefits relatives, increasing shared genetic fitness.

Hamilton’s Rule

A quantitative measure that predicts when natural selection will favor altruistism among related individuals, accounting for B, benefit to the recipient, C, the cost to the altruistic, and R, the coefficient of relatedness or fraction of shared genes.

Plant Behavior (Phototropism, Photoperiodism)

Physical and Chemical Mechanisms

Phototropism: Growth in response to light stimulus

Photoperiodism: Changes in physiological activity based on seasonal light availability

Physical Defenses: Thorns, bark and trichomes help protect against herbivores

Chemical Defenses: Toxins and distasteful compounds deter predators

Ecosystem

All the biotic(living) and abiotic(non-living) factors in a given area.

Metabolic Rate

The amount of energy an organism uses over a period of time.

Inversely proportional to body mass(smaller animals have higher metabolic rates)

Endotherms

Warm-blooded animals that maintain a constant internal temperature and require more energy.

Ectotherms

Cold-blooded animals that rely on environmental heat sources, using less energy.

The Energy Pyramid

A representation of how energy moves through an ecosystem via trophic levels.

1. Primary Producers: Autotrophs that create energy through photosynthesis(sunlight) or chemosynthesis(chemicals)

2. Primary Consumers: Herbivores, heterotrophs, that eat producers.

3. Secondary Consumers: Heterotrophs that eat herbivores.

4. Tertiary Consumers: Heterotrophs that eat other secondary or tertiary consumers.

5. Decomposers: Heterotrophs that break down dead organic material and recycle nutrients.

Food Webs

A diagram that shows the transfer of energy through an ecosystem using arrows(pointing in the direction of the energy flow).

Primary Production and Secondary Production

Gross Primary Production (GPP) is the total energy converted into chemical energy.

Net Primary Production (NPP) is the energy available to consumers after autotrophs use some for respiration.

Secondary Production is the energy transferred to higher trophic levels.

Only 10% of energy is passed between trophic levels, most is lost as heat.

Biogeochemical cycles

Cycles through which matter moves in ecosystems.

1. Water Cycle: includes evaporation, condensation, precipitation, groundwater flow

2. Carbon Cycle: moves carbon between the atmosphere, organisms, and fossil fuels, influencing climate change

3. Nitrogen Cycle: converts atmospheric nitrogen into usable forms through fixation, assimilation, and decomposition

4. Phosphorus Cycle: Vital for DNA and ATP, cycles through rocks, water, and living organisms

Population (and Population Ecology)

A group of individuals of the same species in the same geographical area.

Population Ecology is the study of the change in population due to births, deaths, immigration and emigration.

Density

The number of individuals per unit area.

Populations exhibit different patterns of Dispersion:

• Clumped: Organisms gather in patches, often due to resource availability

• Uniform: Organisms are evenly spaced apart, often due to territorial behavior

• Random: No predictable patter

Life Tables

Survivorship Curves

Life Tables track survival patterns over time.

• Type I: High survival in early/middle life

• Type II: Steady mortality rate

• Type III: High early mortality rate

Population Growth Models

Exponential (J-curve) and Logistic (S-curve)

An exponential curve shows rapid growth and occurs in ideal conditions.

A logistic curve shows growth slowing as it reaches the carry capacity and occurs when density exceeds resource availability.

Life History

The schedule and traits that affect an organism’s schedule of reproduction and survival.

This depends on

1. when reproduction begins

2. how often the organism can reproduce

3. the number of offspring produced per reproductive episode

K-selection (density-dependent selection)

a reproductive strategy

Produces few offspring, high parental investment

This is sensitive to population density and seen in high density populations that are close to carrying capacity (K).

R-selection (density-independent selection)

a reproductive strategy

Produces many offspring, low parental care

Density-Dependent Factors

Factors that affect the population more as population density increases

• Competition for Resources: competition for limited resources increases (food, space, water)

• Predation: denser populations attract more predators

• Disease: Diseases spreads quicker because individuals are in closer proximity

• Parasitism: Increase in parasites spreading among individuals

Density-Independent Factors

Factors that affect the population regardless of population density

• Weather (storms, droughts, heat waves)

• Natural Disasters (floods, fires, earthquakes)

• Human Activities (Habitat destruction, pollution, deforestation)

Community

The group of different species that coexist and interact in a certain geographical area.

Habitat

The physical location where an organism lives.

Niche and Ecological Niche

All species in a community have a specific role, or niche: the full range of conditions and resources that an organism needs to survive, reproduce, and thrive.

The ecological niche is the role a species plays within its habitat, including its interactions with other species and its use of resources.

Fundamental Niche vs Realized Niche

Fundamental Niche: the potential range of conditions a species can tolerate and the resources it could theoretically use in the absence of competition and limiting factors

Realized Niche: the actual conditions and resources a species uses, considering ecological pressures such as competition, predation and disease

Competition

an interspecific interaction

when two species vie for the same resources, such as food, space and light

Competitive Exclusion Principle

Two species that occupy the same niche cannot exist indefinitely if resources are limited, as one will outcompete the other.

Niche Partitioning

The division of resources to minimize direct competition.

Through this, species can coexist by utilizing different resources or utilizing them at different times or in different ways.

Predation

an interspecific interaction

Cryptic Coloration, Batesian Mimicry, Mullerian Mimicry

The interaction where one species, the predator, hunts and consumes the other, the prey.

This relationship drives the evolution of defensive traits in prey species:

• Cryptic Coloration: prey species blend into their surroundings to avoid detection by predators

• Batesian Mimicry: a harmless species resembles a dangerous or poisonous species to deter predators

• Müllerian Mimicry: two harmful or poisonous species resemble each other to reinforce predator avoidance

Herbivory

a type of predation

The interaction where herbivores feed on plants.

This relationship drives evolution of traits in both plants and herbivores.

• Plants evolve physical defenses like thorns or produce toxins. Herbivores may evolve mechanisms to counter these defenses.

Symbiotic Relationships

Facilitation, Parasitism, Mutualism, Commensalism

Interactions where two or more species live together in close association

• Facilitation: at least one species benefits and neither are harmed

• Parasitism: one species benefits at the expense of another, typically harming the host species

• Mutualism: both species benefit

• Commensalism: one species benefits and the other is unaffected

Species Diversity

The variety and abundance of different species within a given ecosystem or community.

Simpson’s Diversity Index (D)

A mathematical formula used to measure the species diversity of a community, taking into account the number of species and the relative abundance of each one.

The higher the value (closer to 1, further from 0), the greater the diversity.

Invasive Species

Non-native species that are introduced to an ecosystem and cause harm by outcompeting local species, altering habitats and disrupting ecological processes.

They reduce species diversity and ecosystem stability.

Keystone Species

A species whose role in an ecosystem has a disproportionately large effect on the structure and diversity of that ecosystem.

They maintain species diversity by preventing any species from becoming overly dominant.

Ecological Disturbances

Events or processes that disturb the structure of an ecosystem.

Ex. Natural disasters, Human Activities

Ecological Succession

The process by which ecosystems develop over time following an ecological disturbance, involving the gradual replacement of species in a community resulting in a more stable, diverse ecosystem.

Primary Succession

an ecological succession

Occurs in areas where ecosystems did not previously exist, such as after a glacial retreat or volcanic eruption.

Begins with pioneer species like lichens and mosses.

Secondary Succession

a type of ecological succession

Occurs in areas where an existing ecosystem was disrupted but soil and some organisms remain, such as after a forest fire or abandoned agricultural land.

Due to the presence of soil and nutrients, this is faster than primary succession.

Human Activities

a major cause of…

A major cause of biodiversity loss and ecosystem disturbance.

• Habitat Loss: the destruction of natural habitats due to human activities, causing species to lose their homes and die off

• Overharvesting: the excessive harvesting of natural resources depleting species populations

• Global Change: climate change and weather patterns can affect temperature, rainfall and resource availability for species

Biogeographic Factors

on the distribution of species across the globe

Latitude: Biodiversity increases closer to the equator because tropical regions typically have more diversity than temperate or polar regions

Area: Larger areas support more species because they provide more habitats and resources. Island ecosystems have fewer species than continental areas.

Pathogens: The spread of diseases drastically affects species populations, especially when species lack immunity or are in stressed environments.