Download Chapter 35 – Population and Community Ecology

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
Introduced species – humans
move species from native
location to new areas they’re
not native to. Ex: Kudzu, Brazilian
Pepper plant.
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
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
Consumers
Consumers 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
Consumers
Also categorized by their position in a
particular food chain.
Primary consumer: when a consumer
feeds directly on producers
Secondary consumer:
eat primary consumers
Tertiary consumers:
third level, eat secondary
consumers
Trophic Levels
Trophic level: feeding level in the
ecosystem
Food chain: the pathway of food transfer
from one trophic level to another
Food 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 REVIEW
1.
2.
3.
4.
5.
6.
What is a producer?
• Organism that makes its own food (plants)
What is a consumer?
• Organism that eats producers (animals)
How do producers fit into the food chain?
• Producers supply all the energy.
How does a herbivore differ from a carnivore?
• Herbivore –eats only plants
• Carnivore – eats only meat
What is an omnivore?
• Eats both plant and meat
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 pathways
8. Explain the rule of 10%.
In a food chain, 10% of the energy made by the
producers is available to the consumer (trophic
level above it) 90% of the energy is lost as heat.
9. What causes the greenhouse effect?
CO2 gets trapped in the earth’s atmosphere
caused 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