Ecology. Part 4. Populations Part 5. Communities Part 6. Biodiversity and Conservation

Transcription

1 Ecology Part 4. Populations Part 5. Communities Part 6. Biodiversity and Conservation

2 Population Ecology: Population Characteristics Population Characteristics 1. Population Density: The number of organisms per unit area 2. Spatial Distribution: Dispersion: The pattern of spacing a population within an area 3 main types of dispersion Clumped Uniform Random The primary cause of dispersion is resource availability

3 Population Ecology: Population Characteristics Population Limiting Factors 3. Population growth rate How fast a given population grows Factors that influence this are: Natality ( birth rate) Mortality ( death rate) Emigration (the number of individuals moving away from a population) Immigration (the number of individuals moving to a population)

4 Population Ecology: Density-independent factors Population Limiting Factors Density-independent factors Factors that limit population size, regardless of population density. These are usually abiotic factors They include natural phenomena, such as weather events Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

5 Population Ecology: Density-dependent factors Population Limiting Factors Density-dependent factors Any factor in the environment that depends on the number of members in a population per unit area Usually biotic factors These include Predation Disease Parasites Competition

6 Population Ecology: Population Growth Rate Understanding Exponentials Put your pens down for a minute & think about this: An employer offers you two equal jobs for one hour each day for fourteen days. The first pays $10 an hour. The second pays only 1 cent a day, but the rate doubles each day. Which job will you accept?

7 Population Ecology: Population Growth Rate Understanding Exponentials Job 1 Job Job 2 lags for a long time before exponential growth kicks in! Now, how much would your employer owe you if you stayed at this job for another 2 weeks? What would happen if this type of growth took place within a population?

8 Population Ecology: Population Growth Rate Population Limiting Factors Population growth models Exponential growth model Also called geometric growth or J-shaped growth. First growth phase is slow and called the lag phase Second growth phase is rapid and called the exponential growth phase Bacteria can grow at this rate, so why aren t we up to our ears in bacterial cells?

9 Population Ecology: Population Growth Rate Population Limiting Factors Population growth models Limits to exponential growth Population Density (the number of individuals per unit of land area or water volume) increases as well Competition follows as nutrients and resources are used up The limit to population size that a particular environment can support is called carrying capacity (k) When you re done writing, put your pens down

10 Population Ecology: Population Growth Rate What population do you think this is?

11 So, what do you think is going to happen to the human population? We will probably reach our carrying capacity. Our growth rate will start to look like most organisms, which is the Logistic Growth Model Carrying Capacity (k) What letter does this curve kind of look like?

12 Population Ecology: Population Growth Models Population Limiting Factors Population growth models Logistic Growth Model Often called the S-shaped growth curve Occurs when a population s growth slows or stops following exponential growth. Growth stops at the population s carrying capacity Populations stop increasing when: Birth rate is less than death rate (Birth rate < Death rate) Emigration exceeds Immigration (Emigration > Immigration)

13 Population Ecology: Population Growth Models Population Limiting Factors Population growth models Logistic Growth Model The S-curve is not as pretty as the image looks 1. Carrying capacity can be raised or lowered. How? Example 1: Artificial fertilizers have raised k Example 2: Decreased habitat can lower k 2. Populations don t reach k as smoothly as in the logistic graph. Boom-and-Bust Cycles Predator-Prey Cycles

14 Community Ecology: Communities Communities Review: A community is a group of interacting populations that occupy the same area at the same time.

15 Community Ecology: Communities Communities Limiting Factors Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.

16 Community Ecology: Communities Communities Range of Tolerance The limits within which an organism can exist.

17 Community Ecology: Ecological Succession Ecological Succession Ecological Succession The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

18 Community Ecology: Ecological Succession Ecological Succession Ecological Succession Consists of 2 types: Primary Succession Secondary Succession

19 Community Ecology: Ecological Succession: Primary Succession Ecological Succession Ecological Succession: Primary The establishment of a community in an area of exposed rock that does not have topsoil is called Primary Succession. It occurs very slowly at first

20 Community Ecology: Ecological Succession: Primary Succession Ecological Succession Ecological Succession: Primary The first organisms to arrive are usually lichens or mosses, which are called pioneer species. They secrete acids that can break down rock Their dead, decaying organic materials, along with bits of sediment from the rock make up soil.

21 Community Ecology: Ecological Succession: Primary Succession Ecological Succession Ecological Succession: Primary Small weedy plants and other organisms become established. As these organisms die, additional soil is created

22 Community Ecology: Ecological Succession: Primary Succession Ecological Succession Ecological Succession: Primary Seeds brought in by animals, water and wind begin to grow in the soil. Eventually enough soil is present for shrubs and trees to grow.

23 Community Ecology: Ecological Succession: Primary Succession Ecological Succession Ecological Succession: Primary The stable, mature community that eventually develops from bare rock is called a climax community.

24 Community Ecology: Ecological Succession: Secondary Succession Ecological Succession Ecological Succession: Secondary Disturbances (fire, flood, windstorms) can disrupt a community. After a disturbance, new species of plants and animals might occupy the habitat.

25 Community Ecology: Ecological Succession: Secondary Succession Ecological Succession Ecological Succession: Secondary Pioneer species in secondary succession are usually plants that begin to grow in the disturbed area. This is much faster than primary succession

26 Community Ecology: Ecological Succession Ecological Succession Ecological Succession: End point? Cannot be predicted Different rates of growth & human involvement make it impossible to know if a true climax community has been reached.

27 Biodiversity and Conservation: Introduction On the left side of your IntNB, address the following: What would happen if all of the jackrabbits in a food web died suddenly? Is the disappearance of one species from Earth important, or will another species fill its niche?

28 Biodiversity and Conservation: What is biodiversity? What is Biodiversity? Biodiversity The variety of life in an area that is determined by the number of different species in that area. There are 2 main types: Genetic Diversity Species Diversity

29 Madagascar Periwinkle: Used to treat childhood forms of leukemia Biodiversity and Conservation: Why is biodiversity important? Biodiversity Penicillin: Derived from bread mold Teosinte: A distant relative of corn Domestic corn plant

30 Biodiversity and Conservation: Extinctions Extinction Rates The gradual process of becoming extinct is known as background extinction. Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time. 250 MYA: Over 90% of species died

31 Biodiversity and Conservation: Extinctions Group Estimated number of Extinctions since Mainland 1600 Island Ocean Total Approximate Number of Species Percent of Group Extinct Mammals Birds Reptiles Amphibians Fish , Invertebrates ,000, Flowering Plants ,

32 Biodiversity and Conservation: Extinctions Five Most Recent Mass Extinctions Cretaceous Period (65 MYA) Triassic Period (200 MYA) Permian Period (250 MYA) Devonian Period (360 MYA) Ordovician Period (444 MYA)

33 Activity: Understanding Geological Time Working in your groups, you will get the following supplies: A meter stick A roll of 5 meters of paper Colored pencils Using the worksheet, plot out the dates. 1 million years is a millimeter 1 billion years is a meter