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Animal Ecology. Chapter 38. Ecology. Ecology investigates the interactions among organisms and between organisms and their environment. Hierarchy of Ecology. Organism level studies focus on individuals. Physiological or behavioral ecology

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animal ecology

Animal Ecology

Chapter 38

ecology
Ecology
  • Ecology investigates the interactions among organisms and between organisms and their environment.
hierarchy of ecology
Hierarchy of Ecology
  • Organism level studies focus on individuals.
    • Physiological or behavioral ecology
  • Population level studies examine groups of conspecific organisms living in a particular area.
hierarchy of ecology4
Hierarchy of Ecology
  • Community level studies investigate interactions between the populations of various species in an area.
    • Species diversity - # of different species
    • Interactions – predation, parasitism, competition, symbiotic associations.
  • Ecosystem level studies examine how a community interacts with the physical environment.
environment and niche
Environment and Niche
  • An animal’s environment includes all of the conditions that affects survival and reproduction.
    • Abiotic factors (nonliving) – soil, air, water, sunlight, temperature, pH etc.
    • Biotic factors (living) – food items, predators, parasites, competitors, mates, hosts etc.
environment and niche6
Environment and Niche
  • Environmental factors that are directly utilized by an animal are resources.
    • Space (nonexpendable)
    • Food (expendable)
environment and niche7
Environment and Niche
  • An animal’s habitat is the space where it lives.
    • Size is variable
      • Rotten log is a habitat for carpenter ants.
      • Forest & adjacent meadow is a habitat for deer.
environment and niche8
Environment and Niche
  • The habitat must meet the requirements for life.
    • Temp, salinity, pH etc.
    • The unique multidimensional relationship of a species with its environment is its niche.
environment and niche9
Environment and Niche
  • Generalists can withstand a variety of environmental conditions.
  • Specialists can only tolerate a narrow range.
environment and niche10
Environment and Niche
  • The fundamental niche describes the total potential role that an organism could fill under ideal circumstances.
  • The realized niche describes the actual role an organism fills.
    • Subset of the fundamental niche.
    • Affected by competition
population ecology
Population Ecology
  • Population ecology is the study of populations in relation to environment, including environmental influences on population density and distribution, age structure, and variations in population size.
populations
Populations
  • A population is a reproductively interactive group of animals of a single species.
    • A few individuals may migrate between populations.
      • Adds gene flow
      • Prevents speciation.
    • Numerous small populations may be connected in this way.
      • Metapopulation
life tables
Life Tables
  • A life table is an age-specific summary of the survival pattern of a population.
    • Life tables usually follow the fate of a cohort – a group of individuals of the same age – from birth until all have died.
survivorship curves
Survivorship Curves
  • A survivorship curve is a graphic way of representing the data in a life table.
  • The survivorship curve for Belding’s ground squirrels shows that the death rate is relatively constant.
survivorship curves15
Survivorship Curves
  • Survivorship curves can be classified into three general types
    • Type I – high survival early in life indicates parental care of fewer offspring.
    • Type II – constant death rate over life span
    • Type III – drops sharply at start indicating high death rate for young; lots of young, no care.
age structure
Age Structure
  • Populations that contain multiple cohorts exhibit age structure.
    • More individuals in the younger cohorts indicates a growing population.
life history diversity
Life History Diversity
  • Species that exhibit semelparity, or “big-bang” reproduction reproduce a single time and die.
    • Salmon
    • Agave
    • Favored in unpredictable climates.
life history diversity18
Life History Diversity
  • Species that exhibit iteroparity, or repeated reproduction, produce offspring repeatedly over time.
    • Lizards often start reproducing during their second year and will produce eggs every year of their lives.
    • Favored in more predictable environments.
population growth
Population Growth
  • It is useful to study population growth in an idealized situation in order to understand the capacity of species for increase and the conditions that may facilitate this type of growth.
population growth20
Population Growth
  • If immigration and emigration are ignored, a population’s growth rate equals birth rate minus death rate.
population growth21

dN

rN

dt

Population Growth
  • Zero population growth occurs when the birth rate equals the death rate.
  • The population growth equation can be expressed as:
exponential growth
Exponential Growth
  • Exponential population growth is population increase under idealized conditions.
    • Unlimited resources.
  • Under these conditions, the rate of reproduction is at its maximum, called the intrinsic rate of increase (rmax).
exponential growth23

dN

rmaxN

dt

Exponential Growth
  • The equation of exponential population growth is:
exponential growth24
Exponential Growth
  • Exponential population growth results in a J-shaped curve.
exponential growth25
Exponential Growth
  • The J-shaped curve of exponential growth is characteristic of some populations that are rebounding.
exponential growth26
Exponential Growth
  • The global human population has been in exponential growth for a long time.
  • At what point will we surpass the carrying capacity for our planet?
logistic growth
Logistic Growth
  • Exponential growth cannot be sustained for long in any population.
    • Depends on unlimited resources.
    • In reality, there are one or more limiting resources that prevent exponential growth.
logistic growth28
Logistic Growth
  • A more realistic population model limits growth by incorporating carrying capacity.
  • Carrying capacity (K) is the maximum population size the environment can support.
the logistic growth model
The Logistic Growth Model
  • In the logistic growth model, the per capita rate of increase declines as carrying capacity is reached.
the logistic growth model30

(K  N)

dN

rmax

N

dt

K

The Logistic Growth Model
  • The logistic growth equation includes K, the carrying capacity.
the logistic growth model31
The Logistic Growth Model
  • The logistic model of population growth produces an S-shaped curve.
the logistic model and real populations
The Logistic Model and Real Populations
  • The growth of laboratory populations of Paramecia fits an S-shaped curve.
the logistic model and real populations33
The Logistic Model and Real Populations
  • Some populations overshoot K before settling down to a relatively stable density.
the logistic model and real populations34
The Logistic Model and Real Populations
  • Some populations fluctuate greatly around K.
the logistic model and real populations35
The Logistic Model and Real Populations
  • The logistic model fits few real populations, but is useful for estimating possible growth.
the logistic model and life histories
The Logistic Model and Life Histories
  • Life history traits favored by natural selection may vary with population density and environmental conditions.
k and r selection
K and r Selection
  • K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density.
    • Few, but larger offspring, parental care.
  • r-selection, or density-independent selection, selects for life history traits that maximize reproduction.
    • Many small offspring, no parental care.
extrinsic limits to growth
Extrinsic Limits to Growth
  • What environmental factors stop a population from growing?
  • Why do some populations show radical fluctuations in size over time, while others remain stable?
extrinsic limits to growth39
Extrinsic Limits to Growth
  • Abiotic limiting factors such as a storm or a fire are density-independent – their effect does not change with population density.
  • Biotic factors such as competition or predation or parasitism act in a density-dependent way – the effect does change with population density.
community ecology
Community Ecology
  • Community ecology examines the interactions among the various populations in a community.
interactions
Interactions
  • Populations of animals that form a community can interact in various ways.
    • Beneficial for one, negative for the other
      • Predation, Parasitism, Herbivory
interactions42
Interactions
  • Beneficial for one, neutral for the other
    • Commensalism
      • Barnacles growing on whales
interactions43
Interactions
  • Beneficial for both
    • Mutualism
interactions44
Interactions
  • Competition is a type of interaction that has a negative effect on both.
    • Community structure is often shaped by competition.
    • Amensalism occurs when only one of the competitors incurs a cost.
      • Balanus & Chthamalus barnacles
competition and character displacement
Competition and Character Displacement
  • Competition occurs when two or more species share a limiting resource.
competition and character displacement46
Competition and Character Displacement
  • Competition is reduced by reducing the overlap in their niches (the portion of resources shared).
    • The principle of competitive exclusion suggests that organisms with exactly the same niche can’t co-occur.
      • One will drive the other out.
competition and character displacement47
Competition and Character Displacement
  • Character displacement occurs when the species partition the resource, using different parts of it.
    • Appears as differences in morphology.
competition and character displacement48
Competition and Character Displacement
  • Species that exploit a resource in a similar way form a guild.
    • Seed eaters vs. insect eaters.
  • A resource (insects) can be partitioned in terms of what part of the tree is searched.
predator prey cycles
Predator-Prey Cycles
  • Many populations undergo regular boom-and-bust cycles.
  • These cycles are influenced by complex interactions between biotic and abiotic factors.
predation
Predation
  • Predation refers to an interaction where one species, the predator, kills and eats the other, the prey.
    • Feeding adaptations of predators include: claws, teeth, fangs, stingers, and poison.
    • Animals also display a great variety of defensive adaptations.
cryptic coloration
Cryptic Coloration
  • Cryptic coloration, or camouflage makes prey difficult to spot.
aposematic coloration
Aposematic Coloration
  • Aposematic coloration warns predators to stay away from prey.
mimicry
Mimicry
  • In some cases, one prey species may gain significant protection by mimicking the appearance of another.
batesian mimicry
Batesian Mimicry
  • In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model.
m llerian mimicry
Müllerian Mimicry
  • In Müllerian mimicry, two or more unpalatable species resemble each other.
species with a large impact
Species with a Large Impact
  • Certain species have an especially large impact on the structure of entire communities either because they are highly abundant or because they play a pivotal role in community dynamics.
keystone species
Keystone Species
  • Keystone species are not necessarily abundant in a community.
    • They exert strong control on a community by their ecological roles, or niches.
keystone species58
Keystone Species
  • Field studies of sea stars exhibit their role as a keystone species in intertidal communities.
keystone species59
Keystone Species
  • Observation of sea otter populations and their predation shows the effect the otters have on ocean communities.
ecosystems
Ecosystems
  • An ecosystem consists of all the organisms living in a community as well as all the abiotic factors with which they interact.
ecosystems61
Ecosystems
  • Ecosystems can range from a microcosm, such as an aquarium to a large area such as a lake or forest.
ecosystems62
Ecosystems
  • Regardless of an ecosystem’s size, its dynamics involve two main processes:
    • Energy flow
    • Chemical cycling
  • Energy flows through ecosystems, while matter cycles within them.
trophic relationships
Trophic Relationships
  • Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) and then to secondary consumers (carnivores).
trophic levels
Trophic Levels
  • Primary production in an ecosystem is the amount of light energy converted to chemical energy by autotrophs during a given time period.
    • Photosynthesis
trophic levels65
Trophic Levels
  • Consumers include:
    • Herbivores – animals that eat plants.
    • Carnivores – animals that eat other animals.
    • Decomposers – feed on dead organic matter.
trophic levels66
Trophic Levels
  • Decomposition connects all trophic levels.
  • Detritivores, mainly bacteria and fungi, recycle essential chemical elements by decomposing organic material and returning elements to inorganic reservoirs.
energy flow
Energy Flow
  • Energy flows through an ecosystem entering as light and exiting as heat.
gross and net primary production
Gross and Net Primary Production
  • Total primary production in an ecosystem is known as that ecosystem’s gross primary production (GPP).
  • Net primary production (NPP) is equal to GPP minus the energy used by the primary producers for respiration.
  • Only NPP is available to consumers.
energy transfer
Energy Transfer
  • The secondary production of an ecosystem is the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period of time.
trophic efficiency and ecological pyramids
Trophic Efficiency and Ecological Pyramids
  • Trophic efficiency is the percentage of production transferred from one trophic level to the next.
    • Usually ranges from 5% to 20%.
pyramids of production
Pyramids of Production
  • This loss of energy with each transfer in a food chain can be represented by a pyramid of net production.
  • A pyramid of numbers represents the number of individual organisms in each trophic level.
pyramids of biomass
Pyramids of Biomass
  • Most biomass pyramids show a sharp decrease at successively higher trophic levels.
    • Occasionally inverted
nutrient cycling
Nutrient Cycling
  • Life on Earth depends on the recycling of essential chemical elements.
  • Nutrient circuits that cycle matter through an ecosystem involve both biotic and abiotic components and are often called biogeochemical cycles.
toxins in the environment
Toxins in the Environment
  • Humans release an immense variety of toxic chemicals including thousands of synthetics previously unknown to nature.
  • One of the reasons such toxins are so harmful, is that they become more concentrated in successive trophic levels of a food web.
toxins in the environment75
Toxins in the Environment
  • In biological magnification, toxins concentrate at higher trophic levels because at these levels biomass tends to be lower.
the three levels of biodiversity
The Three Levels of Biodiversity
  • Genetic diversity comprises:
    • The genetic variation within a population.
    • The genetic variation between populations.
  • Species diversity is the variety of species in an ecosystem or throughout the biosphere.
  • Ecosystem diversity identifies the variety of ecosystems in the biosphere.
endangered species
Endangered Species
  • An endangered species is one that is in danger of becoming extinct throughout its range.
  • Threatened species are those that are considered likely to become endangered in the foreseeable future.
ecosystem services
Ecosystem Services
  • Ecosystem services encompass all the processes through which natural ecosystems and the species they contain help sustain human life on Earth.
    • Purification of air and water.
    • Detoxification and decomposition of wastes.
    • Cycling of nutrients.
    • Moderation of weather extremes.
    • And many others.
four major threats to biodiversity
Four Major Threats to Biodiversity
  • Most species loss can be traced to four major threats:
    • Habitat destruction
    • Introduced species
    • Overexploitation
    • Disruption of “interaction networks”
extinction
Extinction
  • Habitat fragmentation increases local extinction and speciation.
  • Species that have larger ranges or better dispersal abilities are better protected from extinction.
extinction81
Extinction
  • There have been five mass extinctions.
    • Each time a large percentage of the species on earth went extinct.