Population Growth

ECOLOGY

Ecology -

 The study of the interactions

between living things and their environments is known as ecology.

Population Ecology

 Is the study of how populations change.

Three factors can affect population size:

the number of births, the number of deaths, and the number of individuals that enter or leave the population.

Population Properties

 We are going to discuss the different population properties:

 Population Growth

 Age Structure of a Population

 Density and Dispersion

 Limiting Factors of Populations.

Population Growth

 The growth of a population is (without migration) = Birth Rate – Death Rate.

 In a perfect environment, with limitless resources, the population growth would be exponential.

Quiz

 1) Define Ecology.

 2) If there is no migration, what does the population growth equal?

Population Growth

 Exponential growth occurs when a

population is in an ideal environment.

Growth is unrestricted because there are lots of resources, space, and no disease or predation.

Population Growth

 However, the resources aren’t limitless, so each environment has a limit of the number of individuals that it can

support. This is called the CARRYING CAPACITY.

 The population will however around the carrying capacity and form a new curve called the logistic.

Population Growth

 Logistic growth is when a population becomes restricted in size because of limited resources.

Population Growth

 Logistic growth forms an S-

shaped curve because it

reaches carrying capacity.

Quiz

 3) When is the population growth exponential?

 4) When is the population growth represented by a logistic?

Age Structure

 Age Structure: look at the different ages of males and females in a population.

Density and Dispersion

 Density: Number of individuals per area or volume.

Density and Dispersion

 Dispersion: How the organisms are distributed

Limiting Factors: Density Independent

 Density independent factors affect the population regardless of the size.

 Some examples would be unusual weather, natural disasters, seasonal cycles, and human activities such as

damming rivers and clear-cutting forests.

Limiting Factors: Density Dependent

 Density dependent factors depend of the density of the population.

 Resource depletion, competition, disease, and predation are all examples of density dependent factors.

Quiz

 5) Define: Density

 Define : Dispersion

 6) What is a Density dependent limiting factor?

What we know and where we’ll go

 We learned about populations, but how do the populations interact?

 Competition

 Predator/Prey

 Symbiosis

Competition

 Competition – occurs when organisms of the same or different species attempt to use a resource in the same place at the same time.

Predator/Prey

 Predation – interaction in which one organism (the predator) captures and feeds on another organism (the prey).

Examples of predators include cheetahs, anglerfish, snakes, whales, etc.

Predator/Prey Cycle

 When the prey are in high numbers, the predators eat and reproduce (have lots of kids).

 The predator numbers are high, they eat a lot of prey, the prey numbers drop.

 When the prey numbers drop, the predators can’t find food, they will die.

 When the predator numbers drop, the prey will be able to reproduce a lot, the prey

numbers increase.

Predator/Prey Cycle

Quiz

 7) Define Competition

 8) Define Prey

Symbiosis

 Symbiosis: when two species interact with each other. There are three

symbiotic relationships:

 Mutualism

 Parasitism

 Commensalism

Symbiosis: Mutualism

1. Mutualism – where both organisms benefit. (ex: flowers and insects, anemones and clownfish)

Symbiosis: Parasitism

 Parasitism – where one organism harms the other organism (the host). (ex: dogs and ticks, mammals and tapeworms)

Symbiosis:Commensalism

 Commensalism – where one organism lives off another with no harm to the

“host” organism. (ex: orchids and trees, barnacles and whales)

Ecological Succession

 As populations interact, they can interact together. The different populations can

move the ecosystem in a direction called Ecological Succession.

 Overtime, the populations will change in a predictable fashion.

 Ecological succession looks at the change of plant life over time.

Quiz

 9) What are the three types of symbiotic relationships?

 10) What does Ecological Succession look at over time?

Primary Ecological Succession

 There are two types of Ecological

Succession: Primary: starts with no life in an area

 Secondary: starts with an area that has been cleared out.

 Primary: Lichens break down rock into soil. Moss grow, then grasses, flowering plants are next, pine trees and finally

deciduous trees.

Primary Succession

Secondary Succesion

 Life was in an area, but the area was cleared.

 Start with dirt, then moss, grasses, flowering plants, pine trees and

deciduous trees.

 Climax community: stable community that will not change anymore.

Secondary Succession

As populations interact, there is a flow of energy.

 All organisms need energy in order to survive. Without energy, the organism will die?

 How do organisms and the ecosystem get energy?

Ultimate source of energy:

 The sun!

 The sun provides the energy that creates wind, starts the water cycle, creates

weather, and allows plants to photosynthesize.

Quiz

 11) What is a climax community?

 12) What is the ultimate source of energy?

Sun

 Wind: The sun will heat up air. The air rises. Other air rushes in to take the place of the rising air…wind.

Sun

 The sun powers the water cycle by

evaporating the water. The wind and the rain fall causes weather. The sun also

creates weather.

Sun

 Sun powers photosynthesis.

Photosynthesis is how the sun’s energy can be transferred to living organisms.

 Organisms that photosynthesize are called PRODUCERS.

 Organisms that eat producers are called CONSUMERS.

Quiz

 13) How does the sun create wind?

 14) What are producers?

Energy Transfer

 The transfer of energy is from producers to consumers. Other consumers can eat consumers.

 From this we can form a food chain that shows the transfer of ENERGY from

organism to organism.

 Grass Cricket Mouse Wolf

 Energy is transferred from the Grass to the Cricket to the Mouse to the Wolf.

Energy Transfer

 The cricket is called the primary

consumer (first consumer), the mouse is a secondary consumer (second

consumer), the wolf is the tertiary consumer (third consumer).

 The primary consumer can be a

herbivore or omnivore. The secondary consumer can be an omnivore or

carnivore.

Food Web

 A number of food chains can form a food web.

Trophic Pyramid

 We can also show the amount of energy found in a food web in a TROPHIC

PYRAMID.

 The different levels of a trophic pyramid represent the amount of energy in each link of the food chain.

 In the food chain, you always start with the Producers. They are the base of the pyramid. The primary consumers will be on top of the Producers and so on…

Trophic Pyramid, part 2

Quiz

 15) Create a food chain with these organisms:

 Hawk, Mouse, Blueberries.

 16) With those animals, create a trophic pyramid.

Trophic Pyramid, 3

 The size of the bar represents the amount of energy at each level.

 Only about 10% of the energy is

transferred from one level to the next, so the levels get smaller and smaller.

Where do the populations live?

 Biosphere – the entire part of the earth where living things exist. This includes soil, water, light, and air. The biosphere can be divided into different biomes.

 Examples of biomes include tundra, grassland, deciduous forest, etc.

 Ecosystem – regions that include both

abiotic and biotic factors. For example, a lake, the surrounding forest, the

atmosphere above it, and the organisms that live in or feed off the lake all count as an ecosystem.

 Community – a group of plants and animals that show some

interdependence. For example, you, your dog, and the fleas on your dog, would all be members of the same community.

 Populations – group of the same organisms, that can successfully

reproduce, that live in the same area.

Ex: pride of lions, troop of gorillas, gaggle of geese.

Levels of Organization



Biosphere



Biomes



Ecosystem

Community

 Population

 Organism

 Habitat – The area where an

organism lives. A habitat includes both biotic and abiotic factors.

Quiz

 17) How much of the energy is passed on from one trophic level to the next?

 18) Provide the levels of organization

from Biosphere  Organism

WHAT SHAPES AN ECOSYSTEM?

 Biotic Factors – anything living that might affect other organisms within an

ecosystem (ex:

birds, trees, mushrooms, bacteria, etc.).

 Abiotic Factors – Physical, or non-living

factors that shape

ecosystems (ex:

temperature, precipitation, wind, soil type, sunlight, etc.).

Part of abiotic Factors: Elements

 Elements cannot be created nor

destroyed. They are cycled. You learned about the water cycle (we’ll go over it

again), and you’ll learn about the sulfur, phosphorus, nitrogen, carbon, oxygen and water cycle.

Sulfur cycle

Phosphorus Cycle

Nitrogen Cycle

Quiz

 19) What is a Biotic Factor?

 20) Where does the nitrogen come from?

Carbon/Oxygen Cycle

Water Cycle

 Niche – The

ecological role and space that an

organism fills in an ecosystem.

 The niche involves both the place

where an organism lives and the roles that an organism does in its habitat.

 Biodiversity – the total of all the different species/organisms in the biosphere.

 Biodiversity is one of Earth’s greatest

natural resources. Species of many kinds have provided us with food, industrial

products, and medicines (painkillers, antibiotics, anticancer drugs, etc.).

Human Impact

 Unfortunately, humans have disturbed the existing ecological balance. Here are some of the consequences.

Quiz

 21) What two process are involved in the carbon and oxygen cycle?

 22) What is Biodiversity?

1. Deforestation - destruction of forests Effects of deforestation:

 soil erosion

 loss of habitat

 species extinction

 global warming

 disease

 pollution

 oxygen reduction.

2. Biological Magnification- concentrations of a harmful substance increase in organisms at higher trophic levels in a food chain or web

Biological Magnification

(ex: build up of DDT threatened

populations of fish-eating birds (ospreys, brown pelicans, and eagles) by making their eggs fragile.

Rachel Carson wrote Silent Spring to let people know of the danger of biological magnification.

3. Global Warming - increase in the

average temperature of the biosphere.

(Climate Change)

 an increase in CO₂ and other

greenhouse gases in the atmosphere

causes heat to be trapped by the ozone layer.

Quiz

 23) List 3 consequences of deforestation.

 24) What is “Climate Change?”

4. Acid Rain - rain made acidic by nitrogen and sulfur in the air, results from burning fossil

fuels.

Acid rain can kill plants by damaging their

leaves and changing in the chemicals in the soil. It may also dissolve and release toxic elements from soil.

5. Loss of Biodiversity – human activity can reduce biodiversity by destroying habitats, hunting species to extinction, introducing toxins into food chains, and introducing invasive species

(ex: Kudzu is considered a noxious weed that climbs over trees or shrubs and grows so

rapidly that it kills them by heavy shading).

6. CFC’s (chlorofluorocarbons) – group of chlorine-containing chemicals once found in aerosol cans, plastics, and coolants.

CFCs are responsible for causing thinning of the ozone layer. The U.S. began reducing the use of CFCs in 1987, but the effects will still be seen for another 50 years.

What Can We Do?

 Sustainable development – using

renewable resources at a rate that does not deplete them. (ex: replanting

harvested trees, prevention of over fishing or hunting). Sustainable

development also emphasizes the use of renewable resources over non-renewable resources.

 Renewable resource – a resource that can be replaced by natural processes

(trees, water, wind, solar)

 Nonrenewable resource – a resource that cannot be replenished by natural processes (fossil fuels: coal, oil, natural gas)

 Conservation – the wise management of natural resources, including the

preservation of habitats and wildlife.

Today, conservation efforts focus on

protecting entire ecosystems as well as single species.

Quiz

 25) What is Sustainable Development?

Quiz Answers:

 1) The study of the interactions between living things and their environments is known as ecology.

 2) Birth Rate – Death Rate

 3) In a perfect environment, with limitless resources, the population growth would be exponential.

 4) Logistic growth is when a population becomes restricted in size because of limited resources.

Quiz Answers:

 5) Density: Number of organisms per area or volume. Dispersion: How the organisms are distributed.

 6) Density dependent factors depend of the density of the population.

 7) when organisms of the same or different species attempt to use a resource in the

same place at the same time.

 8) Organism that is captured and used for food.

Quiz Answers

 9) Mutualism, Parasitism, and Commensalism.

 10) Change of plant life over time.

 11) A stable community that will not change anymore.

 12) The sun.

 13) The sun heats up air, the air rises, air rushes in to replace the rising air.

 14) Producers will photosynthesize.

Quiz Answers

 15) Blueberries  Mouse  Hawk

 16) Hawk

 Mouse

 Blueberries

 17) 10%

 18) Biosphere  Biome  Ecosystem  Community  Population  Organism

 19) Biotic Factors – anything living that might affect other organisms within an ecosystem (ex: birds, trees, mushrooms, bacteria, etc.).

Quiz Answers

 20) From the atmosphere.

 21) Photosynthesis and Respiration

 22) Biodiversity – the total of all the different species/organisms in the biosphere.

 23) soil erosion

 loss of habitat

 species extinction

 global warming

 disease

 pollution

 oxygen reduction

Quiz Answers

24) increase in the average temperature of the biosphere. (Climate Change)

 an increase in CO₂ and other

greenhouse gases in the atmosphere

causes heat to be trapped by the ozone layer.

 25) using renewable resources at a rate that does not deplete them.