Ecology

ecology : the study of the interactions of living organisms with one another and with their environment

Populations

A population consists of all the individuals of a species that live together in one place at one time.

All the people on earth

All the E. coli in your gut

The two goldfish in your bowl

A population’s future survival is determined by its size,

density, and dispersion.

How are size, density, and dispersion factors in the success of ants?

Patterns of dispersion

How can each pattern affect the success of a population?

Carrying capacity

the population size of the species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment.

Why will the human population growth curve eventually change from an exponential curve to a logistic curve?

Density dependent vs density independent factors

• Density dependent: resources that are depleted such as food and water

• Density independent: environmental factors such as weather and climate

Are predators density dependent or density independent factors?

The Hardy-Weinberg Principle

• The frequencies of alleles and genotypes remain constant in populations in which evolutionary forces are absent

• Evolutionary forces include: mutation, migration, non-random mating, genetic drift, and environmental changes.

Will the population in your goldfish bowl evolve? Why or why not?

Ecosystems

• A community is a group of species that lives together in the same place

• An ecosystem is the community plus the non-living environment

Ecosystems change through the process of succession

Primary succession occurs in a newly formed habitat

Example: After a glacier recedes, the newly exposed land has few nutrients

Pioneer plants (lichens & mosses) begin to grow. Then grasses and shrubs take over. They add nitrogen to the soil.

As the amount of soil increases, trees become plentiful and create shade, eliminating the short plants.

Can you think of other examples of newly formed habitats?

Secondary succession occurs in habitats that previously supported growth

Example: A field that has been cleared of forest.

No two successions are alike. They depend on initial conditions, chance, weather, etc.

How is the soil different in primary and secondary successions?

Energy moves through ecosystems

• Energy cannot be created or destroyed. It can only be changed from one form to another.

• All of the energy on the earth originates from the sun.• The radiant energy from the sun is stored as chemical

energy in plants through the process of photosynthesis.

Energy Flow in Ecosystems

The sun: the source of all the energy on the earth

Producers capture and store energy.

Examples: plants, cyanobacteria, algae.

Also known as autotrophs

Consumers eat (consume) other plants and animals to obtain energy.

Examples: everything except for producers.

Also known as heterotrophs.

Trophic Levels

• “Troph-” means “food” or “nutrition.”

• “auto-” means “self”

• “hetero” means “different” or “other”

A Trophic level is a step in a food chain or food pyramid

A food chain is a single path of energy in an ecosystem

Food Webs• Energy doesn’t

flow in simple straight paths

• Animals often feed at different trophic levels

Why does a food web make a more stable ecosystem than a food chain?

Energy pyramidtrophic levels

Herbivores eat plants

Omnivores eat plants and animals

Carnivores eat animals

Why are the lower levels more diverse and more stable?

Wait! What about the “The circle of life?”

• Decomposers, also called detrivores, obtain their energy from waste and dead bodies at all trophic levels.

• This releases the energy back into the environment to be used by others.

worms

bacteriafungus

Energy transfer• The chemical energy

in food is transformed by an organism into kinetic energy (movement) and heat energy, which is lost to the environment.

• The energy stored in a trophic level is one tenth of that stored in the lower level.

Community Interactions

• Some interactions among species are the result of a long evolutionary history in which many of the participants adjust to one another over time.

• Back-and-forth evolutionary adjustments between interacting members of an ecosystem are called Coevolution

Symbiosis: two or more species living in a close, long term association

Predation• One organism killing another for food

predatorprey

parasitism

• One organisms feeds on and harms another

A tick feeding on a dog

Mutualism• Both organisms benefit

Aphids secrete honeydew for the ants

Ants protect the aphids

commensalism

• One organism benefits and the other is not affected.

The sea anemone protects Nemo, the clownfish

The anemone does not seem to benefit

BiogeochemicalCycles

Or, Nature Doesn’t Throw Anything Away

The Carbon Cycle• All organic life consists of

carbon, hydrogen, oxygen, nitrogen, and sulfur in large quantities

• Other inorganic molecules are also necessary

• They pass through the non-living environment through the living environment, and back to the non-living environment.

All organic molecules have carbon

• Is there carbon in sugar? • Is there carbon in CO2 ?

Matter cannot be created or destroyed

• The Earth has only a fixed amount of carbon. • Carbon is the ultimate form of recycling.

Carbon enters living organisms through plants and other autotrophs

• How do plants use carbon? – Photosynthesis –

• Takes CO2 from atmosphere and combine with water

Heterotrophs Eat the Plants

• Heterotrophs are non-photosynthetic organisms– Cannot create their own food– Break down sugar and starches through cellular

respiration– What are the products of cellular respiration?– Energy

– H2O

– CO2

– CO2 goes back to the atmosphere to use again.

What Eats Animals at the top of the food chain?

• Decomposers are involved in the carbon cycle– Break down organic materials

• Dead plants and animals• Feces

– Produces gasses• CO2 and Methane

p. 352

Carbon atoms may return to the pool of carbon dioxide inthe air and water in three ways.

1. Respiration. 2. Combustion. 3. Erosion.

The Nitrogen Cycle

• What is Nitrogen? – An element just like

carbon– Nitrogen is a part of

PROTEINS– Nitrogen is a part of DNA

• Where is Nitrogen?– 97 of the atomosphere– Most plants and animals

cannot use it in its diatomic state (N2)

– It must be fixed (put in a biologically useful compound)

Nitrogen Cycle

1. Nitrogen fixing bacteria in plant roots convert it to ammonia

2. Decomposers also convert waste into ammonia

3. Then bacteria convert the ammonia to nitrates

4. Plants absorb the nitrates through the roots

Nitrogen Cycle

5. Herbivores eat plants and convert many of the amino acids into new proteins

Omnivores eat both plants and animals and convert into new proteins.

The final step

6. Nitrogen atoms are returned to the soil in feces and dead animals

Once in the soil the process happens again!

Nitrogen Cycle: Bacteria carry out many of the important steps in the nitrogen cycle, including the conversion of atmospheric nitrogen into a usable form, ammonia. p. 353

The Water Cycle

Precipitation

Transpiration

Runoff

Condensation

EvaporationEvaporation

Percolationinto soil

groundwater

lakeocean

clouds

Water vapor

BIOMES

A Biome is a major biological community that occurs over a large area.Biomes are influenced by latitude, temperature, rainfall, soil, wind, and elevation

60 N

30 N

E

30 S

60 S

Tropical Rainforest

Latitude:Temperature:Rainfall:Importance:

Tropical Savanna

Latitude:Temperature:Rainfall:Importance:

Taiga

Latitude:Temperature:Rainfall:Importance:

Tundra

latitude:Temperature:Rainfall:Importance:

Desert

Latitude:Temperature:Rainfall:Importance:

Temperate GrasslandLatitude:Temperature:Rainfall:Importance:

Temperate Forest

Deciduous

Pine

Latitude:Temperature:Rainfall:Importance:

Aquatic Biomes

Freshwater

Life ZonesProfundal

LimneticLittoral

Marine