1. Population Growth What is Population Growth?
An increase in the size of a population over time
Some things exhibit Linear Growth
As time goes by, growth occurs at a steady rate
when graphed, it is a straight line
These slides coincide with the Smartboard titled, “02 Bio 6.2 Population Growth and Limiting Factors”
H – 18.4 p , 19.1 – 19.2 p , 20.2 p
CP – 4.3 p.90-93, 5.1 p
Concepts:
Density Dependent / density independent
Exponentiual growth
Carrying capacity
Biotic / abiotic

2. How do Populations Grow?
Populations show a J-shaped curve
Initial increases are slow, but as the population gets larger, it grows faster
Why? There are more organisms available to reproduce
This pattern is called Exponential Growth

3. Can it go on Forever?
Eventually, population growth will be affected by limiting factors
Such as: availability of food and space
The number of organisms an environment can support is called the Carrying Capacity
In time, the population growth will level off making an s-shaped logistical growth
curve

4. Environmental Limitations
Two main types of Limitation Factors
Density-Dependent
Density-Independent
Density-Dependent Factors have an increased effect as population increases (more organisms, more risk)
Disease
Competition
Parasites
Predation

5. Environmental Limitations
Density-Independent Factors affect all populations regardless of their density (more organisms, same risk)
Temperature
Storms
Natural Disasters
(floods, hurricanes, etc)
Drought
Habitat Destruction
Pollution
Most are abiotic factors

6. Energy Flows through an Ecosystem in a Complex Network of Feeding relationships called a FOOD WEB.
This slide deck corresponds to the Smartboard titled, “3.6 Energy Flow in Ecosystem parts 1-2”.
Reading
H – 18.3 p
CP – 4.2 p.86-89, 20.1 p. 474
Concepts:
Food Chain / Food Web
Producers/consumers/autotrophs/heterotrophs
Trophic levels
Pyramids – biomass/number/energy

7. Food Web

8. Food Chain Food chain: one series of trophic levels
Food chain is one series of trophic levels

9. Obtaining Energy
Autotrophs - use the continuous supply of energy from the sun
Heterotrophs – must consume their energy, relying on the flow of energy from one population to another
Herbivores
Carnivores
Omnivores
Detritivore (AKA decomposers)

10. Herbivores
Eat plants (autotrophs)

11. Carnivores Eat other heterotrophs Predators – kill their own food
Scavengers – eat animals that are already dead

12. Omnivores
Eat both autotrophs and heterotrophs (plants and animals)

13. Detritivore
AKA decomposers – decompose organic matter and return nutrients to soil, water, and air
Ex. fungus, bacteria

14. Energy Pyramid The energy pyramid is made of several trophic levels
A Trophic Level (or feeding level) is a group of organisms whose feeding source is the same number of steps from the Sun.
Primary Producers (Autotrophs) are the First Trophic Level.
Primary Consumers (Herbivores) are the Second Trophic Level.
Secondary and Tertiary Consumers (Carnivores and Omnivores) are the Third and Fourth Trophic Levels.
Most Animals feed at more than one Trophic Level.

15. Trophic Levels
Energy is Lost or Used as it Flows through the Trophic Levels of an Ecosystem.
Producers (Plants) absorb Energy from the Sun, but only about ½ of the Energy capture from the Sun becomes part of the Plants Body. The other ½ is used for Living and Growing or Lost as HEAT.
At each Trophic Level, the Energy stored in an organism is about 1/10 that of the Level Below it. (10%).

16. Trophic Levels
Because Energy diminishes at each successive Trophic Level, Few Ecosystems can contain more than 4 or 5 Trophic Levels.
Organisms at Higher Trophic Levels, Large Carnivores, tend to be Fewer in number than those at Lower Trophic Levels, Producers.

17. Number and Biomass Pyramids
The number of organisms at each trophic levels decreases as you step up the pyramid.
Biomass (living organic matter) is reduced at each trophic level as well

18. Bioaccumulation/Biomagnification
Energy is not the only thing that is passed along through the food web.
If contaminants are introduced at any level, those organisms that consume the contaminated food, will absorb the contaminants as well.
Because the amount of energy required gets higher at each level, those organisms have to consume more and thus can accumulate higher levels of the contaminants in their bodies – bioaccumulation.
Example – A pesticide that you put of your yard is consumed by the grasshoppers that live there. The partridge eats grasshoppers. The hawk eats 3 partridges.
If the grasshopper consumed 1 mg of the pesticide, the partridge ingested 10mg, and the hawk consumed 30mg.