V. Hassell Biology: The Dynamics of Life

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.

Why do weeds grow in areas where other plants die? Lack of rainfall causes most plants to die

Limiting factors restrict the Existence numbers Reproduction distribution of organisms

Mouse population is decreasing.

What factors could cause the fish to look like this

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

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

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

First species to move into an area Lichens Small plants Grasses

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

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

1. Filling a lake or pond to be replaced with a (marsh, dry land, forest). 2. abandoned farms 3. fires or other disasters- 4. diseases & droughts

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

- 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 sampling- Instead of counting all the objects, a representative number is counted Counting populations Tagging animals Marked w ear tags Transmitters Trees w paint or ribbons Clumping groups together

Billions/date/time taken ,000yrs years years years years years Future billion estimated by 2100.

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?

disease Mid 14th Century- Black Plague Reduced England's pop. By 50% from Famine Starvation Irish Potato Famine of the 1840’s killed 1 million A Famine in China during killed 9 million Pop. Change due to Disease The more densely populated- the faster the disease spreads Held pop. In check for thousands of years

Emigration- moving out of an area- decreases pop. Immigration- moving into an area- increases pop Legal immigration in US

Reproductive rate -only long term method of control

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

Freshwater zones of a lake Estuaries salt marshes Marine (Saltwater) sea shores coral reefs ocean