AP Biology: Unit 8

Ch 1: responses to the environment

EQ: why do animals do what they do?

The how and why of animal activity

Behavior is an action carried out by muscles under control of the nervous system

Ex: acquiring food, finding mates, maintaining homeostasis

Behavior is subject to natural selection, and can even influence evolution of animal anatomy

Ethology- study of animal behavior (Niko Tinbergen)

Behavior ecology- study of the ecological and evolutionary basis of animal behavior

Behavior examples:

Innate- fixed action patterns (sticklebacks) or imprinting (young geese)

Learned- learned behavior comes from watching other animals and from life experiences

Associative- classical conditioning (Pavlov’s dogs)

Altruistic- reduces fitness of individual but may increase fitness of population (naked mole rat)

Ch 2

EQ: how do we define ecology, and how do we determine the distribution of organisms?

Ecology- scientific study of interactions between organisms and environment

Organismal ecology- individual living thing… considers how its structure, physiology and behavior meet environmental challenges

Population ecology- group of individuals of the same species living in an area… considers factors affecting population size over time

Community ecology- groups of populations of different species in an area… considers how interactions between species affect community structure and organization

ecosystem ecology- community of organisms in an area AND the physical factors w which they interact… emphasizes energy flow and chemical cycling between organisms and the environment

Landscape (or seascape) ecology- mosaic of connected ecosystems… focuses on the factors controlling exchanges of energy, materials and organisms across multiple ecosystems

Global ecology-

• considers all of biosphere (global ecosystems)… sum of entire planet’s ecosystems and landscapes

• Examines influence of energy and materials on organisms across the biosphere

Distribution- how organisms are spread across a geographic area

Transplants

• organisms intentionally or accidentally moved to areas where previously absent

• Successful transplants indicate that the species’ potential range is larger than its actual range

Density- # of individuals per unit area or volume

Dispersion- movement of individuals (or gametes) away from area of origin or centers of high population, a subsequent density pattern of spacing among individuals

Extrapolation- can be used to estimate densities and total population sizes when impractical or impossible to count all individuals in a population

Ch 3

EQ: how do we calculate population growth?

Idealized vs realistic growth

• unlimited growth occurs under ideal conditions; but in nature, growth is limited by various factors

• Ecologists study growth in both idealized and realistic conditions

Frequency of an event, such as birth or death, can be calculated per person in a population to illustrate population growth

Per capita- a Latin term meaning “by head” that is often used in place of “per person” in statistical observances

Changes in population size

• population growth rate can be expressed mathematically…

  N/t= B - D And N/t= dN/dt

Where N is the change in population size, t is the time interval, B is the number of births, and D is the number of deaths in the population during the time interval

Change in population size = births + immigrants entering population - deaths - emigrants leaving population

Exponential growth

• occurs under idealized conditions= food is abundant and all individuals reproduce at physiological capacity

  • under such conditions, population increases in size by a constant proportion at each instant in time

Exponential growth is represented by the equation

dN= change in population size

dt= change in time

N= population size

r max= maximum per capita growth rate of population

Exponential growth

dN/dt= r max N

Exponential Growth

• population growing exponentially increases at a constant rate ( r )

• Results in a J-shaped growth curve

• Higher intrinsic rate would mean steer growth curve

Carrying capacity

• exponential growth assumes unlimited resources- not realistic!!!

• Carrying capacity (k) is maximum population size in a particular environment can support

• As a population approaches carrying capacity, per capita birth rate will decrease or per capita death rate will increase

Logistic growth model

• per capita rate of increase approaches zero as the population density approaches carrying capacity= (no growth)

Logistic growth can be mathematically represented using an equation

dN= change in population size

dt= change in time

N= population size

K= carrying capacity

r max= maximum per capita growth rate of population

Logistic growth

dN/dt= r max N( K-N/K)

Logistic growth results in a S-shaped curve when resources are limited

Logistic model and real populations

• fits few real populations since some populations overshoot M before settling down row relatively stable density, or some populations fluctuate greatly and make it difficult to define K

“Trade-offs” and selection type

r- selection produces many offspring that grow rapidly due to lower probability of survival to maturity (little care from parents)

k-selection produces few offspring that have higher probability of survival to maturity (higher level of care from parents)

Population density and change

Density independent- birth/death rate does not change with population density

Density dependent- birth decreases with density, or death rate increases with density

Factors of …

density independent:

Flood, fire, pesticide, temperature/ climate change, destruction of habitat, drought

Density dependent:

Food shortage, competition for mates or habitat, increased predation, parasite/ infectious disease, introduction to invasive species, competition for water/ resources

Ch 4

EQ: how does earth’s climate affect the distribution of species?

Determining climate

• long-term weather conditions for a particular location

• Four major abiotic components of climate:

  • sunlight

  • Precipitation

  • Temperature

  • Wind

Biomes- major ecological associations that occupy broad geographic regions of land or water

Biomes disturbances

Environmental change could mean previously unfavorable random genetic mutation/ variation could become advantageous

Humans can create drastic habitat changes or introduce new species

Intentional/accidental introduction of invasive species could lead to increased competition and pre-existing species exploiting a new niche

Ch 5

EQ: how can interactions between organisms be classified, and how can we track the flow of energy?

Symbiosis- interaction between organisms living in proximity… organized as having positive (+), negative (-), or no effect (0) on the survival/reproduction of interacting individuals

Instances:

Competition (-/-)

Individuals of different species compete for resource(s) that limits survival/reproduction of each

Ex. Weeds compete w garden plants for nutrients and water

Exploitation (+/-)

One species benefit by feeding on (and thereby harming) another species

Ex. Predation, herbivory and parasitism

Mutualism (+/+)

Benefits members of both interacting species (sometimes one or both cannot survive w/o the other)

Ex. Clownfish and sea anemones

Commensalism (+/0)

Benefits individuals of one species w/o harming or helping individuals of the other species

Ex. Cows graze in fields and move insects out of grass where egrets can catch and eat them

Ecological niche- specific set of resources (biotic and abiotic) used by an organism

• resource partitioning allows similar species to coexist if one or more significant differences in their niches

Trophies level- occupied position in food web

• feeding relationships are key factors affecting community structure and dynamics

Food chain and food web

Arrow always points to stomach of animal

10% rule- 10% of energy is transferred from one trophicnlevel to the next level (1000 → 100)

Keystone species

• exert strong control on a community by their pivotal ecological roles rather than relative abundance Ex. Yellowstone grey wolves regulate prey populations, enabling other species of plants and animals to flourish

Ecosystem engineers

• cause physical changes in the environment that affect community structure Ex. Beaver dams can transform landscapes on a large scale

ch