Ecology

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Ecology

Ecosystem- a community of organisms living in a particular environment and the physical elements in that environment with which they interact.

-Can be as small as an aquarium or as large as an ocean.

-Includes animals, plants, bacteria, soil, gases, sunlight, etc

2 Categories of factors

Biotic factors- the living parts of an ecosystem

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Biosphere

-

the layer around the Earth in

which life occurs naturally.

Parts of an Ecosystem

Organism- an individual form of life that is a body made up of organs, organelles, or other parts that work together to carry on the processes of life.

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Population- a collection of organisms of a particular species

Community- collections of plants and animals that share an environment

Biodiversity- the variety of organisms found in a given ecosystem

Population Dynamics

• Key Features that help determine the future of

a population.

population size- the number of individuals in a population

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Types of Dispersion

population density- the number of individuals

that live in a given area

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Population Growth

• A population grows when

more individuals are born

than die in a given period.

Exponential Growth Curve- a graph that

represents a J-shaped population growth. Shows that the rate of population growth stays the same (population is increasing steadily).

Only one population has

Shown exponential growth for a long period of time…..

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• Most populations don’t following exponential growth because of carrying capacity.

Carrying capacity- the population size that an environment can sustain.

• Instead, populations usually follow

logistic growth

Logistic growth is a population model where exponential growth is limited by

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Density Dependent Factors

• The rate at which resources are depleted. This rate is influenced by a population’s density.

• When a population is below carrying capacity resources are in abundance.

The growth rate is rapid

• As the population approaches carrying

capacity resources decline and competition increases. Death rates begin to rise and birth rates decrease. The growth rate slows.

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Scientists are concerned that

the human population has

reached carrying capacity.

Food resources decrease. Predator survival

rate decreases (no prey to eat).

Space becomes limited. When organisms live

closer together disease is spread more easily

and quicker.

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Survivorship Curves

• Type 1 Survivorship - The young and those at reproductive age have a high probability of surviving.

– Typically K strategists with long life spans, slow

development, late reproduction, large body size, and low reproductive rate.

• Type 3 Survivorship – High infant mortality.

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Movement Of Energy

• Trophic levels-

one of the steps in a food

chain/food pyramid

• Producers-

an organism that can get

energy from inorganic molecules.

photosynthetic autotroph-

makes

energy from sunlight

chemosynthetic autotroph-

makes

energy from chemicals

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Primary Productivity- determines the amount of energy available in an

ecosystem.

Only 10% of the energy in one level is available to the next level.

Consumer- all organisms that consume plants or other organisms to get energy

Primary consumers- are animals that eat plants or are herbivores

Secondary consumers-are animals

that eat plants and animals (omnivores)

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Biological magnification

• The increase of concentrations of toxins

(pesticides, herbicides, waste) as you

move up the trophic levels.

-Primary consumers must ingest a large amount of primary producers (remember- only 10% of

energy is available to the next level). This causes the concentration of toxins in primary consumers to increase. Secondary consumers must ingest more amounts of primary consumers to get the needed energy. And so on…

By the time you reach tertiary consumers the

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Keystone Species

• A keystone species has a large effect its environment, despite its limited population size.

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Species Interactions

• Niche- “The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism's "address", and the niche is its "profession", biologically speaking.”

Odum - Fundamentals of Ecology - W B Saunders 1959

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EXAMPLE: Oak trees:

• absorb sunlight by photosynthesis;

• absorb water and mineral salts from the soil; • provide shelter for many animals and other

plants;

• act as a support for creeping plants; • serve as a source of food for animals;

• cover the ground with their dead leaves in the autumn.

Niche

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Types of Relationships

• Parasitism- organisms that live in or on another

organism and feeds on it without immediately killing it. Most organisms are negatively affected.

Ex: A hookworm attaches itself on the lining of the intestines and

absorbs the nutrients taken in by the host.

• Mutualism- a cooperative partnership between

two species in which both species benefit

Ex: The acacia tree provides ants with shelter, protein and nectar and the ant provides the

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• Commensalism-

a relationship in which one

species benefits and the other is neither

harmed nor helped

.

Ex: Cattle Egrets eat the flies that are stirred up by grazing cows

•

predation-

one organism kills and eats another.

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Competitive Exclusion Principle

• To reduce competition between different species, one species excludes another from its niche.

– Resource Partitioning – Species coexist by occupying different ecological niches.

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Convergent Evolution

Convergent Evolution In Action

• Batesian Mimicry – A defenseless species resembles a species that is harmful in some way.

• Mullerian Mimicry – All species that are

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Animal Behavior

• Innate behavior is developmentally fixed and does not vary among individuals

• Learning is the modification of behavior based on specific experiences

– Imprinting is the establishment of a long-lasting behavioral

response to a particular individual (usually within a critical period at a young age)

– Habituation is a type of learning that occurs when an animal ignores a repeated, irrelevant stimulus.

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Imprinting

Learning and problem

solving Cognition

Social learning

Spatial learning

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Mating Behaviors

• In monogamous relationships, one male mates with one female.

– Usually occurs in species with high levels of parental care.

• In polygamous relationships, an individual of one sex mates with several individuals of the other sex.

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Sexual Selection

• Sexual dimorphism (a phenotypic difference

between males and females) results from sexual

selection, a form of natural selection.

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Altruism and Hamilton’s Rule

• Kin selection is the natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives.

• Three key variables in an altruistic act

– Benefit to the recipient (B) – Cost to the altruistic (C)

– Coefficient of relatedness (the fraction of genes that, on average, are shared; r)

• Natural selection favors altruism when

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Parent A Parent B

Sibling 1 Sibling 2 ½ (0.5)

probability

OR

½ (0.5)

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Changes of Ecosystems

Over Time

• Succession- a regular progression of species

replacement in an ecosystem.

• Primary succession- succession that occurs where life has not existed before.

Ex: A new Hawaiian Island that forms from a volcanic eruption.

• Secondary succession- succession that occurs in

areas where there was previous growth.

Ex: The re-growing of a forest after a forest fire.

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pioneer species- the first organisms to colonize a new habitat.

Usually plants, lichens, and mosses

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Primary Succession After a glacier retreat

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Biogeochemical Cycles

Biogeochemical cycles-

the circulation of

substances through the biosphere

WATER CYCLE

1. evaporation-

the sun heats the water and

turns it into water vapor

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3. precipitation-

clouds get heavy

and fall as snow, sleet, rain,

and hail

4. Run-off-

precipitation runs off over

the soil and collects in lakes,

rivers, streams (all of these lead to the ocean)

5. transpiration-

after passing through a plant

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Carbon Cycle

• Photosynthetic organisms convert CO₂ to organic

molecules that are used by heterotrophs.

• CO₂ is taken up by the process of photosynthesis

and released into the atmosphere through cellular respiration

• Volcanic activity and the burning of fossil fuels also

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Consumers Consumers Decomposition Photosynthesis Cellular respiration Photo-synthesis Phyto-plankton

CO₂ in atmosphere

Burning of fossil fuels and wood

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Nitrogen Cycle

• Nitrogen is a component of amino acids,

proteins, and nucleic acids

• The main reservoir of nitrogen is the

atmosphere (N

₂

), though this nitrogen must

be converted to NH

₄+

or NO

3−

for uptake by

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• Organic nitrogen is decomposed to NH

₄+

by ammonification, and NH

₄+

is

decomposed to NO

₃−

by nitrification

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The nitrogen cycle Fixation Denitrification Runoff N fertilizers Reactive N gases Industrial fixation N₂ in

atmosphere

NO₃−

NH₄

Dissolved organic N NO₃−

Aquatic cycling Decomposition and sedimentation Terrestrial cycling Fixation in root nodules Decom-position N₂

NO3−

NH4

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Phosphorus Cycle

• Phosphorus is a major constituent of

nucleic acids, phospholipids, and ATP

• Phosphate (PO

₄3−

) is the most important

inorganic form of phosphorus

• The largest reservoirs are sedimentary

rocks of marine origin, the soil, oceans,

and organisms

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Wind-blown dust

Geologic

uplift Weatheringof rocks

Decomposition Plankton Dissolved Uptake Leaching Decomposition Consumption Runoff

PO₄3−

Plant uptake of PO₄3−

Sedimentation