3 Communities and Biomes

V. Hassell Biology: The Dynamics of Life

Objectives

Identify Common

Limiting Factors

Explain how limiting

factors and ranges of

tolerance affect

distribution of

organisms

Sequence the stages

of ecological

succession

Describe the

conditions under

which primary and

secondary succession

take place.

Predict

Why do weeds grow

in areas where other

plants die?

Lack of rainfall causes

most plants to die

Life in a Community

Limiting factors restrict the

Existence

numbers

Reproduction

distribution of organisms

What are the limits of tolerance below?

Mouse

population

is

decreasing.

Limiting Factors

What factors could

cause the fish to look

like this

Ecological Succession

an existing community is gradually replaced by another communityEach new community makes it harder for previous ones to survive

primary succession

Occurs in an area where there has been no previously living community—Weathering rock erodes to soilTakes 200 – 1000 years to make 1 inch of topsoil

climax community

- final stable community that forms if land is left undisturbed. It is relatively stable

pioneer species

First species to move

into an area

Lichens

Small plants

Grasses

secondary succession

Secondary succession is the sequence of changes that takes place after an existing community is severely disrupted in some way Re-establishment or replacement of an existing ecosystem

Mt. St Helens- Washington- 44,460 acres burned and flattened Yellowstone-fire

Iceland- by 1850, all trees were gone- left barren and tundra like- seeds had to be imported

Secondary succession

occurs in areas that previously

contained life, and on land that

still contains soil.

Secondary succession occurs in

areas that previously contained

life. Soil must be present on

this land, and the species that

grow will differ from pioneer

species

Yellowstonebefore & after the fireFire is now recognized as necessary to some ecosystems

Primary and Secondary Succession

What type of succession?

What type of succession?

Which type of succession?

1. Filling a lake or pond to be replaced with a (marsh, dry land, forest).2. abandoned farms3. fires or other disasters- 4. diseases & droughts

Think-Pair-Share

Plan an investigation by writing two

questions that would test temperature as

a limiting factor for an organism in an

ecosystem.

High temperatures

Low temperatures

Dynamic Entity

- there is a constant addition of new members through reproduction & a constant loss through death. balance = reproduction = death

Biotic Potential- maximum growth rate in ideal conditions- how big- how many offspring?Environmental Resistance- all factors which cause early death-

lack of space, food, waste buildup

Population size & arrangement

Population sampling- Instead of counting all the objects, a representative number is counted

Counting populationsTagging animals Marked w ear tagsTransmittersTrees w paint or ribbonsClumping groups together

Population changes flu map

Human Population- It took 10,000 years to reach 1 billion

Billions/date/time taken1 1830 10,000yrs2 1930 100 years3 1960 30 years4 1975 15 years5 1986 11 years6 1999 13 yearsFuture- 10-30 billion estimated by 2100.

0

1

2

3

4

5

6

8,000

BC

1500 Future?

What causes population changes?

Problems w increasing human pop. Producing food for everyone. Should countries with surpluses give it to those without enough?Countries don’t grow at same rate. Should gov. control family size?Poisons used to control pest are poisoning food. Should they be banned?

Population changes due to

disease Mid 14th Century- Black Plague Reduced England's pop. By 50% from 1348 - 1379.FamineStarvation Irish Potato Famine of the 1840’s killed 1 millionA Famine in China during 1877- 1888 killed 9 million

Pop. Change due to Disease The more densely populated- the faster the disease spreadsHeld pop. In check for thousands of years

Population

Emigration- moving out of an area- decreases pop.Immigration- moving into an area- increases pop

Legal immigration in US 1820-1987

Reproductive rate-only long term method of control

Problems with an increasing Human Population

½ of the humans that die each year are under the age of 5Problems feeding all the peopleEspecially in the countries where there is hungerChemicals used to increase food production

Aquatic- Covers 75% of Earth divided into

Freshwater

zones of a lake

Estuaries

salt marshes

Marine (Saltwater)

sea shores

coral reefs

ocean