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.