Biology UNIT 3

Life in a Community+ Succession

Recall: What is a community?

Limiting Factors in a Community

A limiting factor is any biotic or abiotic factor

that resists the existence, numbers, reproduction,

or distribution of organisms.

Common limiting factors include sunlight,

temperature, water, nutrients, fire, soil chemistry,

and space.

Limits of Tolerance

The ability of an organism withstand fluctuations

in the environment.

Too much fluctuation will surpass the tolerance

of the organism.

Limits of Tolerance

Succession

The orderly, natural changes and species

replacement that takes place in the

communities of an ecosystem.

Occurs in stages.

Often difficult to observe because it takes

centuries.

2 Types: Primary and Secondary

Succession

Primary Succession

Takes place on barren land. (No Life, No Soil)

Ex: Lava flows that destroy everything

Starts with pioneer species

Pioneer species are usually mosses and lichens.

Eventually enough moss/lichens will die and

create organic material for soil.

After many years, this area may become a

climax community

Secondary Succession

Takes place after an existing community is

disrupted.

Ex: Forest fires

Because soil already exists, it may take less time

to become a climax community.

Compare/Contrast a

Primary+Secondary Succession

Biomes

A large group of ecosystem that share the same

type of climax community.

Can be terrestrial or aquatic.

Aquatic Biomes

Marine: Saltwater

Estuary: Mixed salt and fresh

Freshwater: Self explanatory

Marine Biomes

Oceans contain huge amount of biomass.

Most of this biomass is tiny creatures like plankton

Separated into photic and aphotic zones.

Photic zone: Shallow waters near landmasses.

Light can reach these areas.

Aphotic Zone: Deepest, least explored parts of

the ocean. No light reaches here.

Estuary

Where river meets sea.

Salinity fluctuates with tides.

Often lush with grasses.

Serves as a nursery for many marine creatures

which in turn attracts many predators.

Freshwater

Often more shallow than marine biomes.

Smaller bodies of water are more prone to

temperature variation.

Greatest biodiversity is in the warmer more

shallow part of lakes and rivers.

Terrestrial Biomes

Affected by latitude and climate.

As climate becomes more temperate, it falls into

the range of tolerance for more organisms

leading to more biodiversity.

Tundra

Closest to the poles

Treeless

Soil lacks nutrients

Extremely short growing seasons for plants.

Home to many small animals, some large

animals may migrate there during summer.

Taiga

Just south of the tundra.

Home to many coniferous trees.

Much of Canada, Northern Europe, and Asia

Soil is acidic and poor in minerals.

Trees provide more shelter and food for animals.

Desert

Dry arid region with sparse plant life.

Less than 25cm of rain

Rain is the major limiting factor for organisms.

Large areas of bare ground.

Many organisms have adaptations to conserve

water.

Grasslands

Between 25cm and 75cm of rainfall

Covered with rich soils and grasses.

Few trees

Often populated by herds of grazing animals

Much more biodiversity than desert

Also called prairie

Temperate Forest

70 to 150 cm of rain annually.

Dominated by broad leafed hardwood trees.

Settlers cleared much of this for lumber.

Soil usually consists of fertile top layer on top of

clay.

Rainforest

200cm to 600cm of rain

Lush plant growth

The most biodiversity of all biomes.

Most nutrients are tied up in biotic factors.

Support a multitude of habitats and niches for

diverse organisms.