Ecology – Part 3 – Honor’s Biology Carrying Capacity Population Growth Human Population Biodiversity

What is a population? Groups of individuals that belong to the same species and live in the same area.

3 characteristics of a population: 1.Geographic distribution: the area inhabited by a population. 2. Population density: the number of individuals per unit area. 3. Population growth: Affected by the # of births, the # of deaths and the # of individuals entering (immigration) or leaving (emigration) the population.

Populations grow if the birthrate is greater than the deathrate. Under ideal conditions with unlimited resources, a population will grow exponentially. This is called exponential growth.

This is represented by a J-shaped curve.

Exponential Growth Curve Population Growth of Houseflies 1 million 500, One year Population size

Carrying Capacity: the largest # of individuals that a given environment can support indefinitely.

Exponential growth does not occur in natural populations for long. Eventually resources (food and space) become less available and growth slows down. This is called logistic growth.

The J-shaped curve levels off as the population reaches carrying capacity (K). This is represented by an S- shaped curve.

In an undisturbed environment (no human intervention), populations will fluctuate around carrying capacity (equilibrium).

Carrying Capacity vs. Exponential Growth J-shaped curveS-shaped curve

Carrying Capacity The maximum number of organisms of a particular type that can be supported in an area…

Carrying Capacity This graph shows an S- curve As the population size approaches the carrying capacity (dashed-line), the growth slows down (note the blue arrows) Time Population

Figure Population cycles in the snowshoe hare and lynx

What limits population growth and maintains balance (equilibrium) in an ecosystem? Density-dependent and density- independent limiting factors

Limiting Factors Limit the organisms that can live in an area: can be biotic can be abiotic

A. density-dependent limiting factors: factors that depend on the population size. The impact increases as the population size increases

What are some factors that would keep the population at a steady level? Competition - organisms struggling for limited resources

A. density-dependent limiting factors: 1. Competition: when the demand for resources such as food, water, space, and other essentials exceeds the supply. Some organisms avoid competition by migrating seasonally to areas where climate is better and more food is available

A. density-dependent limiting factors: 2. Predator-prey relationships: controls numbers of predators and prey. Out-of-Phase Fluctuation

Figure 41.9 Bulk-feeding: a python

A. density-dependent limiting factors: 3. Parasitism and Disease: crowding leads to an increase in parasitism and resistance to disease.

B. density-independent limiting factors: affects all populations in similar ways, regardless of the population size 1. Unusual weather: such as extreme hot or cold temperatures

2. Natural disasters: such as hurricanes, tornados, floods, or droughts. 3. Human activity: such as damming a river or clear-cutting a forest.

PBL Task #3 Before climate change activities such as acid rain and ground level ozone appeared, did your organism display a J-shaped or S-shaped growth curve? What about now? How long will it be or do you think it will be before your organism may be close to reaching their carrying capacity? What are some reasons they may or may not be able to regain their original population? Please be specific with your answers! Explain how the biodiversity of your organism’s environment has changed in the last years. Look at the slides about Human Population and do the Age Structure Activity with your group members. Everyone must have their OWN graph!

4.2 Human Population Demography – the study of human population size –Census –Birth rate (live births/1000 people) –Death rate (deaths/1000 people) –Birth rate – death rate = Population Growth Rate (PGR)

Human Population

Human Population (con’t)

Age Structure Graph – number of people at each different age - see p.103 in textbook

Age Distribution Graphs Activity You will get this from your teacher.

Really cool Population Website!!

Population Biology

Biodiversity A wide range of different species of organisms living in an ecosystem More biodiversity = More stability in the ecosystem –Biodiversity – forest –No biodiversity – corn field Biodiversity allows ecosystems to better survive a catastrophic environmental event If an invasive species enters an ecosystem what happens to biodiversity and why? –It decreases because this affects the food chain of the organism it invades!

Figure Which forest is more diverse?

Biodiversity Smart Board See p.8, 9

Biodiversity – True or False?

Answers –9. true –10. false –11. false –12. true –13. false –14. true –15. true

Let’s go over Bioaccumulation! See Ecology GP #4

Complete the Age Distribution Graphs Activity At some point you need to answer any questions from the back of the paper and turn yours in!

Please read about succession on the following slides We may/may not briefly discuss succession This information will help you understand the process and possibly help with the Succession lab and worksheet Please let me know if you have any questions

Ecosystem Formation Ecological Succession –Replacement of one community by another Pioneer organisms –The first organisms in an area (lichens, algae) –They make a more favorable environment for other plants –Lichens, algae, grass Climax community –The final community –Remains until nature destroys

Forest Succession

Primary Succession- takes place where no life has existed before.

Lake Succession

Secondary Succession – occurs where life has previously existed

Pioneer Species

Think-Pair-Share Which kind of succession would take place? – A forest that has had a fire – A volcano erupting and leaving open rock – A beach affected by a hurricane – A Sand dune in a former desert where the temperature has dropped drastically the last 10 years.

Think-Pair-Share Which kind of succession would take place? – A forest that has had a fire – A volcano erupting and leaving open rock – A beach affected by a hurricane – A Sand dune in a former desert where the temperature has dropped drastically the last 10 years.

Succession Lab Activity and Worksheet Make sure you are working on this in your groups and for homework! You will turn in the completed Lab Activity on the day of or the day after the test! Then, you will begin PBL Task #4!! See the Ecology Part 4 Powerpoint!