POPULATIONS AND COMMUNITY INTERACTIONS

Population growth

What are some of the factors that

affect the size of a

population?

Four factors affect the size of a population

Immigration: when individuals move into a population´s range. (Imigração)

Birthrate: number of individuals that are born in a population in a period of time. (Natalidade)

Emigration: when individuals move out of the range. (Emigração)

Death rate: number of individuals that die in a population in a period of time. (Mortalidade)

Individuals are ADDED to the population

Individuals are REMOVED from the population

Community Interactions

One population

benefits from it but the

other is not affected by it

One population

benefits from it and the other is

harmed by itOne population is harmed by it but the other is not affected by it

Both populations benefit from

the interaction

Both populations are harmed

by the interaction

Competition: same or different species (Competição)

Organisms attempting to use the same ecological resource at the same time and place.

Populations inhibit one another (both populations are harmed by the interaction).Two gazelles competing for land.

Predation: one organism captures and feeds on another organism (Predação)

Predator-prey relationship: (Relação predador-presa)

• One animal (predator) captures and feeds on another animal (prey).

• Lions and buffalo

Who is the predator and who is the prey?

Predation

Herbivore-plant relationship: (Herbivoria)• One animal (herbivore) feeds on

plants.• Caterpillar and plants

Symbiosis: two species living closely together (Simbiose)

Mutualism (Mutualismo)• It is obligatory; both populations benefit from

the relation.• Legume plant and nitrogen-fixing bacteria

located in nodules on their rootsThe bacteria helps the plant to absorb water and minerals. The plant produces organic food for itself and also for the bacteria.

Symbiosis

Protocooperation (Protocooperação)• It is NOT obligatory; both populations

benefit from the relation.• Birds and cows

The bird eats ticks or lice, that are parasites of cows.

Symbiosis

Parasitism (Parasitismo)• The parasite (A) exploits the host (B), but does

not kill it outright.• Ticks (A) and dogs (B)

• “Athletes foot” on human• Worms and human intestine

The tick eats skin and blood of the dog.

Symbiosis

Commensalism (Comensalismo)• The commensal (A) benefits while the host (B)

is not affected.• Remora fish (A) and sharks (B)

Remora fish swims attached to the shark -so that it uses the host as transport, protection and also feeds on food remains.

Symbiosis

Amensalism (Amensalismo ou antibiose)• One species (A) produces a chemical compound

(as part of its normal metabolic reactions) that is harmful to the other species (B) A unaffected; B inhibited.

• Fungus (A) and bacteria (B)The fungus (Penicillium) produces antibiotics, penicillin, that limits the bacterial (Staphylocoque) growth.

Symbiosis

Inquilinismo• An specie (A) uses another one (B) as a place to

live (like a house) but doesn't actually use any resources from B.

• Epiphytes (A) and trees (B) The bromeliad gets all it's nutrients from the environment AROUND the tree. The tree neither benefits nor is harmed by the bromeliad "setting up residence" in it's branches.