Community Ecology

A Community Includes All Life in an Area

Niche: “JOB”

The sum total of all the ways as organism utilizes the resources of its environment

Such as: space utilization, food consumption, temperature range, moisture requirements, etc.

Fundamental niche – entire niche a species is CAPABLE of using

Realized niche – actual niche a species occupies

NOTE:

Niche is NOT the same as habitat HABITAT – a physical place NICHE – pattern of living The niche of a lion – predator Turkey vulture – scavenger Cacti – drought tolerant species

Biotic Interaction

Competition Predation Symbiosis

Competition

Interspecific competition – two different species attempt to utilize the same resource

Intraspecific competition – two members of the same species fighting for same resource

Organisms may occupy more than one niche Gauses’ Rule: No two organisms may

occupy the same niche for very long when resources are LIMITING

“Survival of the fittest” – the stronger will force the weaker out of the habitat or contribute to its demise

This is known as the Competitive Exclusion Principle

Resource Partitioning

The reduction of competition of resources between species by “subdividing the niche”

Warblers: (5) species that fed on insects of spruce trees One species fed on insects near branch tips One fed on dense foliage One fed on bases of tree branches One on the tree top One on the tree bottom

Each bird fed on different insects by feeding at different levels of the spruce tree – different niches

Sympatric species – differentiation of populations into different species within the same geographical areas (brown/green anole) Partition resources by feeding in

different portions of the habitat, utilizing different foods, feeding at different times

Believed to be driven by natural selection

Allopatric Populations

The differentiation of geographically isolated populations into distinct species

Predators

Consuming of one organism by another Predators (or lack of) can often have large effects

on prey populations

Eastern Coast

- population explosions of white-tailed deer – strip the habitat of all edible plant life

Western Coast

- sea otters hunted to near extinction – sea urchin populations exploded (otters eat urchins)

Predation

Prey ↑ = Predator ↑ Prey ↓ = Predator ↓ Predator ↑ = Predator ↑ = Prey ↓

How Would Evolution Apply?

Evolution – change in a species over time Adaptation – species becomes better suited

for survival Natural selection - “survival of the fittest”

PREDATOR – strong selective pressure on prey Only the strongest, quickest prey survive – prey evolve

defensive adaptations Also only the strongest, fastest predators will survive

Plant Defenses against Herbivores Morphological defenses – thorns, spines,

prickles, and plant hairs

Chemical defenses – toxic to most herbivores or disturb their metabolism (mustard, cabbage, watercress, radish, and horseradish, the same taste we enjoy!)

Animal Defenses against Predators Defensive Coloration –

Cryptic coloration – color that blends with the surroundings and thus hides the individual from predators *usually do not live together in groups*

Warning coloration – showy coloration that shows they are poisonous

Chemical Defenses – Poisons and Stings

Mimicry – looking like a harmful organism Batesian Mimicry – palatable insects having

coloration of a distasteful insect Monarch and viceroy butterflys

Mullerian Mimicry – the resemblance of dangerous, unpalatable, or poisonous species (even unrelated species) to one another so that they become more easily recognized by potential predators Brightly colored species of poison dart frogs

Coevolution

long-term mutual evolution of members of biological communities

Ex. Predator-Prey interactions

Flowers and pollinators

A Type of Co-evolution

Symbiotic relationships – two or more kinds of organisms live together in elaborate and permanent relationships

Example:

Fungi and roots of plants – fungi and expedite the plants’ absorption of nutrients and the plants in turn provide the fungi with carbohydrates

Kinds of Symbiosis

Commensalism Mutualism Parasitism Saprophitism

Commensalism

One species benefits while the other neither benefits nor is harmed

Example: Epiphytes on trees (epiphytes – plants that

live on other plants) Vermiliads and orchids in rain forest

Mutualism

Both participating species benefit

Example:Cattle egret on back of cow

Parasitism

One species benefits but the other is harmed Ex. Tapeworm in dog Tick on human

3 Types of Parasites

External – parasites that feed on the exterior surface ex. Lice

Internal – parasites that feed on the interior

*not bacteria of fungi*

Brood – ex. Birds lay eggs in nests of other species

Keystone Species

Species that have a particularly strong effects on the composition of communities

Examples:

Dung beetle

Beavers

Succession

Change in which one ecosystem is replaced by another

ex. Pond becoming a forest, field becoming a marsh

Primary Succession

where there has been no life previously

Occurs on bare, lifeless substrate when organisms gradually move into an area and change its nature

Ex. sand dune, lava, bare rock

Secondary Succession

where life has existed previously a wooded area is cleared and left

alone, plants will slowly reclaim the area

ex. After a forest fire, a fallow field

Why Succession Happens

Species alter the habitat and the resources available in it in ways that favor other species.