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Animal Ecology

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Title: Animal Ecology


1
Animal Ecology
  • Chapter 38

2
Ecology
  • Ecology investigates the interactions among
    organisms and between organisms and their
    environment.

3
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.

4
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.

5
Environment and Niche
  • An animals 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.

6
Environment and Niche
  • Environmental factors that are directly utilized
    by an animal are resources.
  • Space (nonexpendable)
  • Food (expendable)

7
Environment and Niche
  • An animals 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.

8
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.

9
Environment and Niche
  • Generalists can withstand a variety of
    environmental conditions.
  • Specialists can only tolerate a narrow range.

10
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

11
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.

12
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

13
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.

14
Survivorship Curves
  • A survivorship curve is a graphic way of
    representing the data in a life table.
  • The survivorship curve for Beldings ground
    squirrels shows that the death rate is relatively
    constant.

15
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.

16
Age Structure
  • Populations that contain multiple cohorts exhibit
    age structure.
  • More individuals in the younger cohorts indicates
    a growing population.

17
Life History Diversity
  • Species that exhibit semelparity, or big-bang
    reproduction reproduce a single time and die.
  • Salmon
  • Agave
  • Favored in unpredictable climates.

18
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.

19
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.

20
Population Growth
  • If immigration and emigration are ignored, a
    populations growth rate equals birth rate minus
    death rate.

21
Population Growth
  • Zero population growth occurs when the birth rate
    equals the death rate.
  • The population growth equation can be expressed
    as

22
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).

23
Exponential Growth
  • The equation of exponential population growth is

24
Exponential Growth
  • Exponential population growth results in a
    J-shaped curve.

25
Exponential Growth
  • The J-shaped curve of exponential growth is
    characteristic of some populations that are
    rebounding.

26
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?

27
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.

28
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.

29
The Logistic Growth Model
  • In the logistic growth model, the per capita rate
    of increase declines as carrying capacity is
    reached.

30
The Logistic Growth Model
  • The logistic growth equation includes K, the
    carrying capacity.

31
The Logistic Growth Model
  • The logistic model of population growth produces
    an S-shaped curve.

32
The Logistic Model and Real Populations
  • The growth of laboratory populations of Paramecia
    fits an S-shaped curve.

33
The Logistic Model and Real Populations
  • Some populations overshoot K before settling down
    to a relatively stable density.

34
The Logistic Model and Real Populations
  • Some populations fluctuate greatly around K.

35
The Logistic Model and Real Populations
  • The logistic model fits few real populations, but
    is useful for estimating possible growth.

36
The Logistic Model and Life Histories
  • Life history traits favored by natural selection
    may vary with population density and
    environmental conditions.

37
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.

38
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?

39
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.

40
Community Ecology
  • Community ecology examines the interactions among
    the various populations in a community.

41
Interactions
  • Populations of animals that form a community can
    interact in various ways.
  • Beneficial for one, negative for the other
  • Predation, Parasitism, Herbivory

42
Interactions
  • Beneficial for one, neutral for the other
  • Commensalism
  • Barnacles growing on whales

43
Interactions
  • Beneficial for both
  • Mutualism

44
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

45
Competition and Character Displacement
  • Competition occurs when two or more species share
    a limiting resource.

46
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 cant
    co-occur.
  • One will drive the other out.

47
Competition and Character Displacement
  • Character displacement occurs when the species
    partition the resource, using different parts of
    it.
  • Appears as differences in morphology.

48
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.

49
Predator-Prey Cycles
  • Many populations undergo regular boom-and-bust
    cycles.
  • These cycles are influenced by complex
    interactions between biotic and abiotic factors.

50
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.

51
Cryptic Coloration
  • Cryptic coloration, or camouflage makes prey
    difficult to spot.

52
Aposematic Coloration
  • Aposematic coloration warns predators to stay
    away from prey.

53
Mimicry
  • In some cases, one prey species may gain
    significant protection by mimicking the
    appearance of another.

54
Batesian Mimicry
  • In Batesian mimicry, a palatable or harmless
    species mimics an unpalatable or harmful model.

55
Müllerian Mimicry
  • In Müllerian mimicry, two or more unpalatable
    species resemble each other.

56
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.

57
Keystone Species
  • Keystone species are not necessarily abundant in
    a community.
  • They exert strong control on a community by their
    ecological roles, or niches.

58
Keystone Species
  • Field studies of sea stars exhibit their role as
    a keystone species in intertidal communities.

59
Keystone Species
  • Observation of sea otter populations and their
    predation shows the effect the otters have on
    ocean communities.

60
Ecosystems
  • An ecosystem consists of all the organisms living
    in a community as well as all the abiotic factors
    with which they interact.

61
Ecosystems
  • Ecosystems can range from a microcosm, such as an
    aquarium to a large area such as a lake or forest.

62
Ecosystems
  • Regardless of an ecosystems size, its dynamics
    involve two main processes
  • Energy flow
  • Chemical cycling
  • Energy flows through ecosystems, while matter
    cycles within them.

63
Trophic Relationships
  • Energy and nutrients pass from primary producers
    (autotrophs) to primary consumers (herbivores)
    and then to secondary consumers (carnivores).

64
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

65
Trophic Levels
  • Consumers include
  • Herbivores animals that eat plants.
  • Carnivores animals that eat other animals.
  • Decomposers feed on dead organic matter.

66
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.

67
Energy Flow
  • Energy flows through an ecosystem entering as
    light and exiting as heat.

68
Gross and Net Primary Production
  • Total primary production in an ecosystem is known
    as that ecosystems 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.

69
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.

70
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.

71
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.

72
Pyramids of Biomass
  • Most biomass pyramids show a sharp decrease at
    successively higher trophic levels.
  • Occasionally inverted

73
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.

74
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.

75
Toxins in the Environment
  • In biological magnification, toxins concentrate
    at higher trophic levels because at these levels
    biomass tends to be lower.

76
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.

77
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.

78
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.

79
Four Major Threats to Biodiversity
  • Most species loss can be traced to four major
    threats
  • Habitat destruction
  • Introduced species
  • Overexploitation
  • Disruption of interaction networks

80
Extinction
  • Habitat fragmentation increases local extinction
    and speciation.
  • Species that have larger ranges or better
    dispersal abilities are better protected from
    extinction.

81
Extinction
  • There have been five mass extinctions.
  • Each time a large percentage of the species on
    earth went extinct.
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