Chapter 35 Population

Population Density• Population-members of the same

species living in a specific area• Population density –

The number of individuals

of a particular species divided by area

or volume. Ex: the number of fish per square kilometer of swamp

Pop. Density = # of Individuals

Unit Area

Population Density• Example:

–What is the population density if there are 500 people in a 100km2 area?

•500/100 = 5 people/km2

Niche• Niche – An organisms unique

living place defined by food, habitat, activity times, breeding, etc.

• A habitat is an organism’s environment (biotic and abiotic).

• No two species can occupy the same niche. But they can occupy the same habitat.

Predation - one organism eats another. Predators are the organisms doing the eating.The organism being eaten is the prey.

Symbiotic Relationships• Symbiosis - A close interaction

between two species.

–Ex: the clown fish and sea anemone.

Types of symbiotic relationships• Parasitism: 1 benefits, the other

is harmed (tapeworm in intestinal tract)

• Mutualism: Both benefit. (Us and bacteria in our intestinal tract)

• Commensalism: 1 benefits, the other not affected (crab which uses seaweed for camouflage)

Symbiosis

Disturbances in Communities • Ecological succession: Process of

community change.

–Primary succession: a community arises

out of a formerly

lifeless area

(no soil).

Ex.:New islands

• Secondary succession: a community changes after a dramatic change in an area where there is soil.

•Fire, volcano, clearing forest

Kudzu kills other plants by smothering them under a solid blanket of leaves, by girdling woody stems and tree trunks, and by breaking branches or uprooting entire trees and shrubs through the sheer force of its weight. Once established, Kudzu plants grow rapidly, extending as much as 60 feet per season at a rate of about one foot per day

Introduced species – humans move species from native location to new areas they’re not native to. Ex: Kudzu, Brazilian Pepper plant.

Energy Flow• How an organism feeds

determines the path of energy in the ecosystem.

–Producers (autotrophs): organism that makes if own food. Ex: Plants

–Consumers (heterotrophs): organisms that eat producers

•Ex: Animals, bacteria

ConsumersConsumers may be:

• Herbivores: animals that eat plants

–Ex: Cows

• Carnivores: animals that eat other animals. Ex: Lions

• Omnivores: eat plants and animals

–Ex: Humans

• Decomposers: organism that breaks down organic waste

–Ex: Bacteria and fungi

Consumer - Decomposer

ConsumersAlso categorized by their position in a particular food chain.

Primary consumer: when a consumer feeds directly on producersSecondary consumer:

eat primary consumersTertiary consumers:

third level, eat secondary consumers

Trophic LevelsTrophic level: feeding level in the ecosystemFood chain: the pathway of food transfer from one trophic level to anotherFood web: A pattern of feeding in an ecosystem consisting of interconnected and branching food chains.

Trophic Levels

Food Chain

Food Web

Energy Flows Through Ecosystems

Ecological Energy Pyramids:

• Illustrates how the energy transfers between trophic levels

-only 10% of the energy of the previous trophic level is

utilized by the next level

–90% is lost as heat.

Biological Magnification

• Pollutants become more and more concentrated as they move up the food chain–Pollutants concentrate in the muscle,

which is eaten. As organisms consume more and more contaminated muscle much pollutant accumulates in their tissues.

–Example: see fig 36-17 PCB’s and DDT pg. 802

Threats to Biodiversity• Habitat destruction is the number

one threat to biodiversity• Other threats to biodiversity

1) Introduced species (like kudzu in Florida)

2) Habitat destruction

3) Overexploitation (killing elephants for ivory)

4) Pollution

Nutrients Cycle Through Ecosystems

• Carbon cycle

–During cellular respiration consumers break down sugars and release carbon dioxide into the atmosphere

–During photosynthesis producers take in carbon dioxide and form sugars

Water Cycle• Condensation-gaseous water

becomes liquid water.• Precipitation-raining• Transpiration-water exits the leaves• Evaporation-liquid water becomes

gaseous water.

-

Nitrogen Cycle• Nitrogen in the atmosphere

• Nitrogen cycle relies heavily on bacteria.

• Bacteria convert ammonium into Nitrates (NO3¯) in the soil for plants to use.

• Animals eat plants and get Nitrogen.

Human Impacts on the Environment

• Burning of fossil fuels –Greenhouse effect - Carbon dioxide

gets trapped in the atmosphere and causes the Earth to heat up.• Caused by the destruction of the ozone layer by chlorofluorocarbons or CFC’s

• In excess this can lead to global warming

LET’S REVIEW1. What is a producer?

• Organism that makes its own food (plants)2. What is a consumer?

• Organism that eats producers (animals)3. How do producers fit into the food chain?

• Producers supply all the energy.4. How does a herbivore differ from a carnivore?

• Herbivore –eats only plants• Carnivore – eats only meat

5. What is an omnivore?• Eats both plant and meat

6. In which category of consumers would we find bacteria?

• Decomposer

7. How does a food chain differ from a food web?– Food chain shows one energy pathway – food

web shows interconnected energy pathways8. Explain the rule of 10%.

In a food chain, 10% of the energy made by theproducers is available to the consumer (trophiclevel above it) 90% of the energy is lost as heat.

9. What causes the greenhouse effect?CO2 gets trapped in the earth’s atmospherecaused by destruction of the ozone layer by CFC’s

10. Why is it bad to spray DDT on crops?• Biological Magnification

11. What is the #1 threat to biodiversity?• Habitat destruction