NOTES ECOLOGY

SPECIES INTERACTION & COMMUNITY DISTURBANCE

I. Populations in Communities INTERACT

A. Competition: struggle for resources between living things

1. Example: a. Interspecific competition: competition between species that depend on the same limited resource

2. Competitive exclusion is when 2 species are so similar in their requirements that the same resource limits both populations’ growth. One species may succeed OVER the other one and take away all the resource.

3. Niche: unique living arrangement of an organism defined by its habitat, food sources, time of day it is most active, and other factors

a. Example: 2 similar lizards, one eats

on tall shrubs, other low shrubs, * if niches

are similar, may see competitive exclusion *

B. Predation

1. One organism eats another

2. Predator --> the hunter

a. Fast and strong

b. Good senses- hearing, sight, smell

c. Camouflage

d. Sharp teeth, claws

3. The Prey --> the food

a. Good eyesight,

hearing, smell

b. Camouflage

c. Fast, agile, some are

poisonous or has

spikes

C. Symbiotic Relationships 1. A close interaction between species in which one of the species lives in or on the other 2. Parasitism: + - one organism benefits (parasite) the other is harmed (host) a. Intestinal worms and animals 3. Mutualism: + + both organisms benefit from each other a. E.coli and people; tube worms and bacteria 4. Commensalism: + 0 Only one organism benefits while the other is NOT harmed, or helped- rare a. Spider crab using seaweed to cover itself to hide from danger

Parasitism

Mutualism

Commensalism

II. Disturbances are Common in Communities

A. Disturbances to communities

1. Fires, volcanoes, floods, storms, droughts

2. Effects can be positive

i. Shipwreck- can be new habitat

ii. Forest fires- some plants sprout

B. Ecological Succession

1. Primary succession: process by which a community arises in a virtually lifeless area with no soil

ex: bare rock, “start from scratch”

i. bacteria, lichens --> moss --> “pioneer organism”

ii. Grasses --> shrubs --> trees

2. Secondary succession: when disturbance damages existing community but leaves the soil in tact

Ex. When a farmer ploughs down

field to dirt, then abandons it

CLIMAX COMMUNITY

When an ecosystem has reached a stage where it doesn’t change very much and the community is fairly stable.

This is the final step in Ecological Succession, although many communities never make it to thi step before another disturbance comes to start the process over.

Human Activity and Species Diversity

Human Disturbances can have a negative or positive effect on the community-- in most cases it is negative.

Examples are:

Clearing of land-- this can be done by making farms, clear cutting for lumber, building roads, buildings or parking lots.

Introduced species-- Species that are moved into an area that they do not normally grow either intentionally or unintentionally. Some of these species do not make it in their new environment but others take over the native (indigenous) species and strip the native species of their resources.