Population, Energy Pyramid & Trophic Levels

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

How do Populations Grow?

• 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

• Populations show a J-shaped curve

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 growthcurve

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

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

Population

Community

Biome

Biosphere

Ecosystem

Organism A single living thing

A group of organisms of the same species that live together.A group of Populations that live together

Communities and their physical environments

A group of ecosystems that have the same climate.

All the biomes on Earth. Thus, all the living areasof the planet.

Levels of Organization

Energy Flow Concept Map

ChemicalCyclesFeeding

Relationships

Energy Flow

TrophicLevels

Key Concept:

One of the ways in which energy flows through an Ecosystem is by feeding. Different living organisms eat each other, and the food is energy moving from one organism to the next.

What is a Food Web?

• The feeding relationships in an ecosystem. Also called a food chain.

Energy Flows through an Ecosystem in a Complex Network of Feeding relationships called a FOOD WEB.

http://www.brainpop.com/science/ecologyandbehavior/foodchains/

Food Web

Trophic level: ConsumersConsumers is a trophic level of heterotrophs

Consumers are heterotrophs which eat other organisms for energy,such as snails and pigs. There are many trophic levels of consumers.

Herbivores eat plants only. (cows)

Carnivores eat animals only. (sharks)

Omnivores eat plants and animals.(humans, mice)

Decomposers break down dead, rotting remains.( bacteria, mushrooms)

Trophic level Pyramid

ProducersAutotrophs

Primary ConsumerHeterotrophsHerbivores

SecondaryConsumer

TertiaryConsumer

Uses the sun’s energy to make its own food- photosynthesis

About 10% of available NRGis passed up

1000

100

10

Trophic level Pyramid

ProducersAutotrophs

Primary ConsumerHeterotrophsHerbivores

SecondaryConsumer

TertiaryConsumer

Uses the sun’s energy to make its own food- photosynthesis

About 10% of available NRGis passed up

1000

100

10The rest is lost asHeat and Waste

Energy Pyramid Further Explainedhttps://www.youtube.com/watch?v=ScizkxMlEOM

Food ChainFood chain: one series of trophic levels

Obtaining Energy

• Autotrophs - use the continuous supply of energy from the sun

• Heterotrophs – must consume their energy, relying on the flowof energy from one population to another– Herbivores– Carnivores– Omnivores– Detritivore (AKA decomposers)

Herbivores

• Eat plants (autotrophs)

Carnivores

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

Omnivores

• Eat both autotrophs and heterotrophs (plants and animals)

Detritivore

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

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 morethan one Trophic Level.

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%).

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.

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

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 10 grasshoppers. The hawk eats 3 partridges. – If the grasshopper consumed 1 mg of the pesticide,

the partridge ingested 10mg, and the hawk consumed 30mg.