Animal Ecology

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

ecologyPopulation level studies

examine groups of conspecific (same species) organisms living in a particular area.

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

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.

Biotic Factors

Abiotic factors

Environment and Niche

Environmental factors that are directly utilized by an animal are resources.Space (nonexpendable)Food (expendable)

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 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 Niche

Generalists can withstand a variety of environmental conditions.

Specialists can only tolerate a narrow range.

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 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

A population is a reproductively interactive group of animals of a single species.A few individuals may migrate between

populations.Adds gene flowPrevents speciation.

Numerous small populations may be connected in this way.

Metapopulation: a regional group of connected populations of a species.

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

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 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.

Life History Diversity

Species that exhibit “big-bang” reproduction reproduce a single time and die. Salmon Agave Favored in

unpredictable climates.

Life History Diversity

Species that exhibit 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

It is useful to study population growth in an idealized (perfect)situation in order to understand the capacity of species for increase and the conditions that may facilitate this type of growth.

Population Growth

If immigration (moving in) and emigration (moving out) are ignored, a population’s growth rate equals birth rate minus death rate.

Zero population growth occurs when the birth rate equals the death rate.

Exponential Growth

Exponential population growth is population increase under idealized conditions. Unlimited resources.

Exponential population growth results in a J-shaped curve.

Exponential Growth

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

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

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 Growth

A more realistic population model limits growth by incorporating carrying capacity.

Carrying capacity (K) is the maximum population size the environment can support.

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 examines the interactions among the various populations in a community.

Interactions

Populations of animals that form a community can interact in various ways. Beneficial for one,

negative for the other

Beneficial for both Or negative for both

How do species interact?

There are 5 types of species interactions. Some of these may be pretty familiar to you. Can you name all 5?

5 types of species interactions: Predation Competition Parasitism Mutualism Commensalism

Each category is based on the effect each species has on the other

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Predation

-Predation is when one organism of 1species (predator) consumes part orall of another organism of anotherspecies (prey)-Can be: herbivores (plant-eaters) orcarnivores (meat-eaters)-This is a win-lose relationship(predator wins, prey loses)

Predation

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Types of predators

Carnivores – kill the prey during attack

Herbivores – remove parts of many prey, rarely lethal.

Parasites – consume parts of one or few prey,rarely lethal.

Parasitoids – kill one prey during prolongedattack.

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How has predation influenced evolution?

Adaptations to avoid being eaten:

spines (cactii, porcupines)hard shells (clams, turtles)toxins (milkweeds, some newts)bad taste (monarch butterflies)

camouflageaposematic colorsmimicry

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Camouflage – blending in

Figure 53.5

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Aposematic colors – warning

Figure 53.6

Go to camouflage video

Mimicry – looks like something that is dangerous or tastes bad

(a) Hawkmoth larva

(b) Green parrot snake

Figure 53.7a, b

Mimicry – look like something that is dangerousor tastes bad

• In Batesian mimicry- one harmless species adopts the appearance of another, harmful species to gain the advantage of predators' avoidance.

• Mullerian mimicry – two or more poisonous species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals.

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.

Predators can affect the size of prey populations in a community and determine the places prey can live and feed.

Herbivory

Herbivory, the process in which an herbivore eats parts of a plantHas led to the evolution of plant mechanical and

chemical defenses and consequent adaptations by herbivores

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A verbal model of predator-prey cycles:

1. Predators eat prey and reduce their numbers

2. Predators go hungry and decline in number

3. With fewer predators, prey survive better and increase

4. Increasing prey populations allow predators to increase

And repeat…

Levels of Ecosystem Organization

There are many different kinds of relationships between organisms we have been talking about today we are going to look at mutualism, where both organisms benefit from the relationship, one type of symbiosisFirst we need to refresh on the levels of organization in an ecosystem.

Using a city park as an example, each group come up with an example of each of the above. You may review the definitions from your notes or book

Let’s look at a short food chain…Grass Rabbit Fox

1. Identify the predator/prey relationship. If the fox hunts and kills the rabbit, could this effect the producer (the grass) in this food chain?

2. Predator-prey relationships are important in ecosystems because they provide a balance between the populations.

3. We are going to use some data to investigate a specific predator-prey relationship.

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Lynx and Snowshoe hare

Video 1 and 2

Symbiotic Strategies

Let’s review different ecological relationshipsWith your group generate a list of types of

interactions that might exist between different species living close to each other.

(EX species A might eat species B, A might use B’s discarded shell etc)

This should focus on interactions between different species, NOT the same species

You have 5 minutes then we will list them on the board.

Symbiotic Strategies

What is the definition for “symbiosis”? Symbiosis is a long-term interaction between different species

that interact in close proximity (live by each other) These symbols represent the 3 types of symbiosis. Can you tell me which one is beneficial to both? Which one benefits one species but doesn’t affect the other? Which one benefits one species but harms the other?

++ +0+-

mutualism

commensalism

parasitism

Symbiotic strategies II Name the types of ecological relationships that were

seen between different species in the video clips. What type of symbiotic relationship was NOT seen in

these clips? parasitism is a symbiotic relationship between two species

living together that provides a net gain for one species and a net loss for the other species.

It is different from predation in that the relationship is prolonged and ideally does not end in the death of the host – the parasite requires its host to remain alive in

order for the parasitic relationship to continue — but it may make the host very sick.

Parasites – yuck!

Name some examples of parasitic relationships between species but some examples include intestinal worms and mammals –

for example the tapeworm and the cow; cuckoo birds and other bird species; and fleas and dogs/cats

that one example of a human parasite is the protozoan that causes the disease malaria

Parasites – yuck!

These protozoans, of the genus Plasmodium, are especially interesting in that they have TWO species that act as their hosts, not just one.

Ask if the students know how malaria is transmitted to humans? The disease is transmitted by mosquitoes

It is not the mosquito itself that is the parasite – it is the protozoan that is transmitted from one animal or person to another via the mosquito’s saliva.

The mosquito is a vector – an organism that transmits disease but does not cause it.

Human interaction

What are the types of ecological relationships we have studied thus far? (predation, competition, mutualism, commensalism,

parasitism) these relationships have evolved over a long period of time

between species that coexist. Even the relationships that are detrimental to one species (i.e.

predation, parasitism) are integral to the maintenance of ecological balance.

threats to this stability can occur when dramatic events or shifts in behavior throw an ecosystem out of whack.

Human Interaction

What are some examples of events and behaviors that may be dramatic enough to threaten the stability of a particular ecological niche human actions, climate change, pollution, etc.

Competition

Competition occurs when two organisms fight for the same limited resource.

Competition can be:• within the same

species (Intraspecific)

• or between different species (Interspecific)

Competition

Example of Interspecific and Intraspecific competition:

Two squirrels race up a tree to reach a hidden pile of nuts. _____________

A hyena chases off a vulture to feast on an antelope carcass._____________

Brown bears hunting for fish on a river’s edge fight over space.____________

How does competition shape communities?

By causing species to divide resources, competition helps determine the number and kinds of species in a community and the niche each species occupies.For Example: In a forest, plant roots

compete for resources such as water and nutrients in the soil.

Animals compete for resources such as food, mates, and places to live and raise their young.

Strong competition can lead to competitive exclusionThe local elimination of one of the two

competing species Direct competition between different species

almost always produces a winner and a loser—and the losing species dies out. This is called the competetive exclusion principle

Resource competition

How one organism interacts with other organisms is an important part of defining its niche.

Competition occurs when organisms attempt to use the same limited ecological resource in the same place at the same time.

However, ecologically similar species can coexist in a community If there are one or more significant difference in

their niches

When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area.

The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realizedniche of Chthamalus much smaller than its fundamental niche.

RESULTS

CONCLUSION

Ocean

Ecologist Joseph Connell studied two barnacle speciesBalanus balanoides and Chthamalus stellatus that have a stratified distribution on rocks along the coast of Scotland.

EXPERIMENT

In nature, Balanus fails to survive high on the rocks because it isunable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata.

Low tide

High tide

Chthamalusfundamental niche

Chthamalusrealized niche

Low tide

High tideChthamalus

Balanusrealized niche

Balanus

Ocean

Figure 53.2

The Competitive Exclusion Principle The competitive exclusion principle states

that no two species can occupy exactly the same niche in exactly the same habitat at exactly the same time.

If two species attempt to occupy the same niche, one species will be better at competing for limited resources and will eventually exclude the other species.

As a result of competitive exclusion, natural communities rarely have niches that overlap significantly.

Resource availability gives structure to a community.Species can share habitats and

resources.

Competition occurs when two species use resources in the same way.

Competitive exclusion keeps two species from occupying the same niche.

4. Possible Outcomes of Competitive Exclusion:a. One species is better suited to the

niche and the other will either be pushed out or become extinct.

b.The niche will be divided.

c. The two species will further diverge.

Interactions

Beneficial for one, neutral for the other Commensalism

Barnacles growing on whales

Interactions

Beneficial for bothMutualism

Interspecific Competition

Competition When two species use the same limited resource to

the detriment of both species. interspecific individuals of different species compete

for the same resource in an ecosystem (e.g. food or living space)

Intraspecific which involves organisms of the same species

Competitive exclusion or coexistence Coexistence: reducing competition by dividing

resources

Assessment

Mechanisms of competition consumptive or exploitative — using resources (most

common) preemptive — using space, based on presence overgrowth — exploitative PLUS preemptive chemical — antibiotics or allelopathy territorial — like preemptive, but behavior encounter — chance interactions

Competition

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 occurs when two or more species share a limiting resource.

If a tree species in a dense forest grows taller than surrounding tree species, it is able to absorb more of the incoming sunlight. However, less sunlight is then available for the trees that are shaded by the taller tree, thus interspecific competition. Cheetahs and lions can also be in interspecific competition, since both species feed on the same prey, and can be negatively impacted by the presence of the other because they will have less food

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 Displacement

Character displacement occurs when the species partition the resource, using different parts of it. Appears as

differences in morphology.

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.

Cryptic Coloration

Cryptic coloration, or camouflage makes prey difficult to spot.

Aposematic Coloration

Aposematic coloration warns predators to stay away from prey.

Mimicry

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

Batesian Mimicry

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

Müllerian Mimicry

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

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 are not necessarily abundant in a community.They exert strong control on a community

by their ecological roles, or niches.

Keystone Species

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

Keystone Species

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