Ecology Branch of biology that studies the interactions between organisms and their environment.

Ecology

•Branch of biology that studies the interactions between organisms and their environment

Biosphere•All of the locations on Earth that can support life

Abiotic Vs. BioticAbiotic

•Non living factor in an environment

Examples•rocks•water•sunlight

Abiotic Vs. BioticBiotic

•Living factors in an environment

Examples•plants•animals•bacteria

Levels of life•Ecologists look at

individual organisms (level 1)

• organisms that have similar characteristics can mate and produce fertile offspring are a species

Population

•Group of organisms of a single species that live in a given area

Community

•A collection of interacting populations in a given area

Ecosystem

Collection of organisms that interact with

each other and with abiotic factors in the

environment

Landscapea group of ecosystems which affect one another

Ecotone (edge effect)a transition area between ecosystems, with blended characteristics

Ecotones are often caused by underlying environmental gradients

Energy in the Ecosystem

Organisms•Autotrophs-make own food producers

•Heterotroph-must get nutrients from outside sources consumers

Organisms

•Carnivore•Herbivore•Omnivore

Organisms

•Decomposers: break down dead organisms into simple molecules

•Scavengers: feed off dead animals

Trophic Level•Feeding level on food, energy, or biomass pyramid

•Starts with primary producers

•Ends with highest level consumer

Food Chain

•One set of organisms moving up through the trophic levels

•Grass mouse fox hawk

Food Web

•Interconnecting food chains in an ecological community

•More than one food chain

Importance of decomposers

• Because of decomposers the same atoms that made up the dinosaur's cells make up our cells!!

Energy Pyramid

•Illustrates that energy decreases at each succeeding trophic level

•Usually square shaped•Only 10% energy moves up

Populations

populations

•Group of organisms of the same species living in the same location

•Change in population size is called growth rate (can be + or -)

Populations Can Grow, Shrink, or Remain Stable

• Population size governed by– Births– Deaths– Immigration– Emigration

• Population change = (births + immigration) – (deaths +

emigration)

Growing population• Ideal conditions• Healthy organisms reproduce

faster• Birth rate is higher than death rate

Species Have Different Reproductive Patterns

r-Selected species

• Short life• Rapid growth• Early maturity• Many small

offspring• Low on trophic level

Characteristics of r-selected reproductive pattern species• Unpredictable

environments• Small body size• Mature rapidly• Reproduce

early• Short life span

Species Have Different Reproductive Patterns

K-selected species

• Long life• Slow growth• Late maturity• Few, larger offspring• High on trophic level

Characteristics of K-selected reproductive species

• Reproduce and mature slowly

• Long-lived• Large body

size

Carrying capacity (k)

•Largest number of individuals that can survive over long periods of time in a given environment

•Size of population is stabilized

Many species grow until capacity is reached and then

level off BUT….

Boom and Bust

Some species - exponential growth and then fast crashcan rise again or wait for some time before another boom

Exponential Growth, Overshoot, and Population Crash of a Reindeer

Density Dependent Limiting Factors

• Operate more strongly on large populations

• Usually works on stable populations

Density Dependant Factors

•Disease•Parasites•Competition (food, space)

•Stress

Density Independent Limiting Factors

• Weather – storms, fires, droughts, heat, cold, floods, hurricanes

• Human activities – toxic waste spill, pesticides, clear cutting

Coevolution

• the evolution of complementary adaptations in two or more species of organisms because of a special relationship that exists between them

Examples

Predator/ prey relationship•Cheetah can run very fast but lacks stamina•Gazelles have evolved stamina to escape cheetahs

Batesian Mimicry

• A harmless species (non poisonous) resembles a poisonous species

Which butterfly has a bitter taste?

Mullerian Mimicry

• Two poisonous species look alike

Queen Butterfly and Monarch are both

poisonous

Population Interactions Influence Abundance

• When populations of different species interact, the effects on one on the other may be positive (+), negative (-) or neutral (0).

• By comparing populations living alone and together, several types of interactions can be identified.

FIVE IMPORTANT INTERACTIONS BETWEEN

TWO SPECIES

• COMMENSALISM (+/0)• MUTUALISM (+/+)• COMPETITION (-/-)• PARASITISM (+/-)• PREDATION (+/-)The symbols +, - and 0 refer to the effect of one

species on another when both are living together.

Competition

LIVING ALONE LIVING TOGETHERCOMPETITION 0 0 - -[When both populations live together, abundance of each is lower.]

Law of Competitive Exclusion• No two species will occupy the same

niche and compete for exactly the same resources for an extended period of time.

• One will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource.

• Given resource can only be partitioned a finite number of times.

Resource Partitioning

Competition• Interspecific - Competition between

members of different species.• Intraspecific - Competition among

members of the same species.– Often intense due to same space and

nutritional requirements.• Territoriality - Organisms defend specific area

containing resources, primarily against members of own species.

• Resource Allocation and Spacing

Intraspecific Competition

• Resource depletion may result in too many individuals in the population. Thus, the population crashes.

• Reindeer on Saint Matthews Island died off as the result of depletion of lichens (food).

Reindeer on St Mathews Island

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Intraspecific Competition

• A seed company tells gardeners that planting plants too far apart or too close together will only produce a few seeds. Why?

Intraspecific Competition

• Territorial behavior has evolved in many species as a response to intraspecific competition.

• Male red wing blackbirds stake out a territory in defense of nests and mates.

Interspecific Competition

Predation

LIVING ALONE LIVING TOGETHER

PREDATION + - - +[Prey (A) are in greatest abundance when predators are absent.

Predators (B) are in greatest abundance when prey are present.]

Predation

• Feeds directly upon another living organism

• Prey most successfully on slowest, weakest, least fit members of target population.– Reduce competition, population

overgrowth, and stimulate natural selection.

symbiosisIntimate living together of members of

two or more species.• Commensalism - One member

benefits while other is neither benefited nor harmed.– Cattle and Cattle Egrets

• Mutualism - Both members benefit.– Bees and flowers

• Parasitism - One member benefits at the expense of other.– Humans and Tapeworms

COMMENSALISM

» LIVING ALONE LIVING TOGETHER A B A B

COMMENALISM 0 0 + 0Species A is more abundant when there are

more of species B present. Species B is not affected by the presence of A

COMMENSALISM

• The cattle egret and cattle or other grazing African ungulate species.

• The egret benefits from catching insects that cattle “scare-up” while grazing.

• Cattle unaffected.

COMMENSALISM

• Bromeliads are a group of flowering plants that attach to trees (epiphytes). They gain access to sunlight and catch water.

• The trees are not harmed or benefited.

Mutualism

LIVING ALONE LIVING TOGETHER A B A BMUTUALISM - - + +[Both populations are found in greatest abundance when

together.]

MUTUALISM

• pollination of flowering plants by an insect or humming bird.

• The pollinator benefits from the interaction by receiving nectar.

• The plant gets its pollen transferred from one plant to another.

MUTUALISM

• The lichen is a mutualistic association between a species of algae and a species of fungus.

• The fungus retains water and takes up minerals.

• The algae provides carbohydrates and other organic nutrients as the result of photosynthesis.

Parasitism

LIVING ALONE LIVING TOGETHERA B A B

Parasitism + - - +

Parasitism• Tick feeds off

mammal benefitting the tick but harming the mammal.

• How would this ecosystem be affected if the butterfly population decreased?

• How would this ecosystem be affected if the coyote population decreased

• How would this ecosystem be affected if the raven population increased?

Limitations of where a species can live

1. Physiological stress due to environmental conditions

2. Competition with other species3. Predation4. Parasitism and disease5. luck

Critical Environmental Factors

• Single factor in shortest supply relative to demand is the critical determinant in species distribution.– Example: a cactus species can not

survive if temperature drops below 30º F for more than 12 hours.

Tolerance Limits

• Each environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive– Combination of many factors:

temperature range, food availability, competitors, predators

Tolerance Limits

Limits of Range1. Physical Barriers

a. Oceans (humans, cattle, marsupials)b. Mountains (house finch)c. Ice (cactus, coral reefs)

2. Climatic3. Altitude4. Food5. Water6. Competitors

Indicators

• If we know the tolerance range of species, we can deduce the conditions in the environment based on the presence of a particular species– Example: trout require cool, clean well

oxygenated water; if you see an abundance of trout, what does that tell you about the environment?

Ecological Niche• Habitat - Place or set of environmental

conditions where a particular organism lives.• Ecological Niche

– Role a species plays in a biological community (e.g. large grassland herbivore)

– Total set of environmental factors that determines a species’ distribution.

– Generalists - Broad niche– Specialists - Narrow niche

• When generalists and specialists collide, generalists usually win.

Generalists

North and Central AmericaOmnivorous: berries, insects, eggs, small animals

Specialists

ChinaEat Bamboo

Keystone Species• A keystone species is a species that plays a

critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass– Large predators– Critical food organisms (bamboo and

pandas)– Often, many species are intricately

interconnected so that it is difficult to tell which is the essential component.

Starfish: Keystone SpeciesFeeds on muscles and sea urchins

Muscles will outcompete other species

Sea Urchins over populate: decrease in corals