Unit XI: Ecology and Animal Behavior

Ecological interactions affect how organisms evolve, and evolutionary

change in turn affects ecological relationships.

EcologyEcology• the study of the relationships between organisms and their environment + two types of interactions

- biotic (living)- abiotic (nonliving)

+ levels of study- population, community, ecosystem, biosphere

• Population Ecology + population: group of individuals all of the same species living in the same area

- describing abundance/distribution of populations + size (total number of individuals = N) + density (total number of individuals per area/volume) + dispersion (clumped, uniform, random)

Age Structure

Sweden- relatively stable population growthMexico- rapidly growing populationUnited States- relatively stable population growth

Survivorship Curves

Type I: most individuals die oldType II: length of survivorship is randomType III: most individuals die young

Population GrowthBiotic potential• maximum growth rate of population under ideal conditions + bacteria divide every 20 minutes + elephants require 2 year gestation period

- factors + age at reproductive maturity + clutch size + frequency of reproduction + reproductive lifetime + survivorship of offspring to maturity

Carrying Capacity (K)• maximum number of individuals a population can sustain + limiting factors

- elements that prevent a population from attaining its biotic potential

Density-dependent FactorsDensity-dependent factor• intensifies as population increases + reduce the population growth by decreasing reproduction or by increasing mortality

- parasites/disease, competition,predation, stress

Density-independent FactorsDensity-independent factor• occurs independently of population; unrelated to population size + natural disasters and extremes of climate

Calculating Growth Rater = births - deaths

Nr = reproductive/growth ratebirths - deaths = net increase of individuals

N • r = births - deaths

ΔN = r • NΔt

represents the change in the number of individuals over a given time

When r is… positive (rmax = intrinsic rate) population size will increase negative, population size will decreasezero, population size remains constant (ZPG)

Exponential Growth

J-shaped curve

Logistic GrowthLogistic Growth• occurs when limitingfactors restrict the sizeof the population to the carrying capacity (K)

ΔN = r • N (K - N)Δt K

• as population increases,r decreases until N = K, and r = 0

S-shaped/sigmoid curve

Life-history Strategies

k selected and r selected species• k selected (prudent or equilibrial populations) + produce small numbers of young; lots of parental care

- long life expectancy strategy + consequences

- increased probability of long term survival- slow to recuperate numbers when population is reduced

• r selected (prodigal or opportunistic populations) + produce many young; very little parental care

- short life expectancy strategy + consequences

- can recuperate numbers quickly following population crash- lead risky lives

Generation Time and Body Size

Which organisms are…r selected?k selected?

What about in the plant kingdom?

Community EcologyCommunity Ecology• looking at the interactions between populations + interspecific/intraspecific interactions

- interactions between populations of different/same species- positive (+), negative (-), or neutral (0)

+ types- Competition- Predation- Symbiosis

CompetitionCompetition (-/-)• interaction between individual organisms that use the same resources present in limited supply

- niche: set of resources/conditions necessary for survival + organism’s role/job in the community- intraspecific/interspecific competition + same/different species- types + Interference Competition

- animals: overt fighting; plants: secretion of toxins + Exploitative Competition

- removal of a resource- Competitive Exclusion Principle- G.F. Gause, Russian biologist

PredationPredation (+/-)• eating of live or freshly killed organisms + predators eat prey + parasitism

- specialized predators do not actually kill prey (host) + Three hypotheses

- When prey population decreases, predator population decreases;When predator population decreases, prey population increases- Prey populations may undergo a regular cycle- Predator populations may undergo a regular cycle

+ Defense against Predators- cryptic coloration (camouflage)- aposematic coloration (warning coloration)- mimicry

+ Batesian (harmless species mimics harmful model)+ Mullerian (harmful species resemble each other)

SymbiosisSymbiosis • close and long term association between organisms of two species + Mutualism (+/+)

- both organisms benefit from the interaction + mycorrhizae, lichens

+ Commensalism (+/0)- one species benefits, but other is unaffected + remora-shark relationship

Community Composition and the Question of Stability

Disturbances• events, such as storms, fire, floods, droughts, overgrazing, etc. + damage community, remove organisms, alter resource availability

- communities are usually in a state of recoveryEcological Succession• change in the composition of species over time + climax community

- final successional stage of constant species composition + changes that induce succession

- substrate texture- soil pH- soil water potential- light availability- crowding

Primary Succession

Primary Succession• occurs on substrates that neverpreviously supported living things + succession on rock or lava

- lichens- bacteria, protists, mosses- insects, other arthropods- r-selected species of plants- k-selected species of plants

Secondary SuccessionSecondary Succession• begins in habitats where communities were destroyed by disturbances + abandoned cropland

EcosystemsTrophic Levels• Primary producers + autotrophs (plants, protists, cyanobacteria, chemosynthetic bacteria)• Primary consumers + herbivores• Secondary consumers + primary carnivores• Tertiary consumers + secondary carnivores• Detritivores + decomposers (fungi, bacteria, earthworms, insects, scavengers)

Pyramid of Energy

Pyramid of Biomass

Pyramid of Numbers

Ecological EfficiencyEcological Efficiency• proportion of energy represented at one trophic levelthat is transferred to the next + average efficiency=10%

- only 10% of productivityis transferred to next level- remaining 90% is consumed by metabolism

Food Chains and Food WebsFood Chain• linear flow chart of who eats whom

grass --> zebra --> lion --> vulture

Food Webs• expanded, more complete

Biogeochemical CyclesBiogeochemical Cycles• flow of essential elements from the environment to living things andback to the environment + reservoirs

- major storage locations + assimilation

- processes through which element incorporates into terrestrial plants and animals

+ release- processes through which element returns to the environment

Hydrologic Cycle (water cycle)

Reservoirs: oceans, air, groundwater, glaciersAssimilation: plants absorb from soil; animals eat/drinkRelease: plants transpire; animals/plants decompose

Carbon Cycle

Reservoirs: atmosphere (CO2), fossil fuels, peat, celluloseAssimilation: plants via photosynthesis; consumersRelease: respiration and decomposition; burn fossil fuels

Nitrogen Cycle

Reservoirs: atmosphere (N2); soil (ammonium, ammonia, nitrite, nitrate)Assimilation: plants absorb from soil; animals consume plants/animalsRelease: denitrifying and detrivorous bacteria; animal excretion

Phosphorous Cycle

Reservoirs: rocksAssimilation: plants absorb from soil (phosphate); consumersRelease: decomposition; excretion in waste products

BiomesBiome• region of biosphere characteristized by vegetation and adaptations of organisms inhabiting the environment + Tropical rain forest (high temp., heavy rainfall) + Savannahs (grassland with scattered trees)

- tropical, but receive less rainfall than rain forest + Temperate grasslands (North American prairie)

- receive less water/lower temp. than savannahs + Temperate deciduous forests (warm summer/cold winters) + Deserts (hot and dry) + Taigas (coniferous forests)

- precipitation in the form of snow + Tundras (Lambau Field)

- permafrost + Fresh water biomes (ponds, lakes, streams, rivers) + Marine biomes (estuaries, intertidal zones, continental shelves, coral reefs, pelagic oceans)

Animal BehaviorEthology• the study of animal behavior• nature versus nurture… both? + kinds of animal behavior

- Innate Behavior + instinct + fixed action patterns or FAP (Niko Tinbergen) + imprinting* (Konrad Lorenz)- Learned Behavior + associative learning

- classical conditioning (Ivan Pavlov) - operant conditioning (B.F. Skinner) + habituation + observational learning + insight

Animal MovementKinesis• undirected change in speed of movement in response to stimulus + speed up in unfavorable; slow down in favorable

- light, touch, air temp., etc. + Avon bug in the bathroom tub

Taxis• directed movement in response to stimulus + toward/away from stimulus

- phototaxis, chemotaxis + mosquitos and CO2

Migration• long-distance, seasonal movement + availability of food, degradation of environment

- whales, birds, elks, insects, bats

Communication in AnimalsWhy do animals communicate? How do animals communicate?Chemical• pheromones + releaser pheromones cause immediate/specific behavioral changes + primer pheromones cause physiological changes

- marking your territoryVisual• agonistic behavior + displays of aggression• courtship behavior + announce participants as non-threatening/potential matesAuditory• sounds + whales, crickets, birdsTactile• touching

Social BehaviorAgonistic Behavior• aggression/submission + competition for food, mates, territory + ritualized; reduces injury/energyDominance Hierarchies• power and status relationships among groups + minimize fighting for food/matesTerritoriality• possession/defense of territory + insures adequate food/spaceAltruistic Behavior• unselfish behavior that appears to reduce fitness + increases inclusive fitness

- ground squirrels