Biotic and Abiotic Influences on Ecosystems

(textbook section 2.7)

Today’s Goals

1.Understand how abiotic factors affect ecosystems

2.Be able to describe some interactions between organisms

3.Describe how humans can affect these interactions

Limiting Factor

Any factor that restricts the size of a population or where it can live

e.g. food availability, disease, predation

Tolerance Range

The range of abiotic conditions within which a species can live

e.g. temperature, light, moisture

Carrying Capacity

• As a population grows, it requires more food, water and space. At some point, the population reaches a maximum number of organisms that can survive. This limit is called the carrying capacity.

Carrying Capacity

The maximum population size of a particular species that a given ecosystem can sustain

e.g. temperature, light, moisture

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Fire and tree cutting can remove shade and expose organisms to more light

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Damming rivers and draining wetlands reduces water availability

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Water Damming rivers and draining wetlands reduces water availability

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Water Damming rivers and draining wetlands reduces water availability

Farming practices can change nutrient levels in soil

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Water Damming rivers and draining wetlands reduces water availability

Nutrients Farming practices can change nutrient levels in soil

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Water Damming rivers and draining wetlands reduces water availability

Nutrients Farming practices can change nutrient levels in soil

Global warming can reduce available habitat for cool-adapted species.

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Key Abiotic Factor

Human action and result

Light Fire and tree cutting can remove shade and expose organisms to more light

Water Damming rivers and draining wetlands reduces water availability

Nutrients Farming practices can change nutrient levels in soil

Temperature Global warming can reduce available habitat for cool-adapted species.

What are some ABIOTIC factors in Ecosystems? How do humans affect

those factors?

Think-pair-share

Try filling out the ‘Aquatic Ecosystems’ chart on your own,

then compare with a partner.

What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?

Key Abiotic Factor

Human action and result

Light Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths

Fertilizer runoff can increase nutrients in the water and cause algal blooms.

Pollution from burning fossil fuels increases acid rain in aquatic ecosystems

Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.

Salting highways and irrigation can increase the concentration of salt.

What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?

Key Abiotic Factor

Human action and result

Light Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths

Nutrients Fertilizer runoff can increase nutrients in the water and cause algal blooms.

What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?

Key Abiotic Factor

Human action and result

Light Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths

Nutrients Fertilizer runoff can increase nutrients in the water and cause algal blooms.

Acidity Pollution from burning fossil fuels increases acid rain in aquatic ecosystems

Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.

Salting highways and irrigation can increase the concentration of salt.

What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?

Key Abiotic Factor

Human action and result

Light Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths

Nutrients Fertilizer runoff can increase nutrients in the water and cause algal blooms.

Acidity Pollution from burning fossil fuels increases acid rain in aquatic ecosystems

Temperature Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.

Salting highways and irrigation can increase the concentration of salt.

What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?

Key Abiotic Factor

Human action and result

Light Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths

Nutrients Fertilizer runoff can increase nutrients in the water and cause algal blooms.

Acidity Pollution from burning fossil fuels increases acid rain in aquatic ecosystems

Temperature Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.

Salinity Salting highways and irrigation can increase the concentration of salt.

What are some ways that BIOTIC factors interact in Ecosystems?

1. Competition• Two or more individuals try to get

enough of one resource• It is a negative relationship because both

organisms are harming each other.• Example: foxes and coyotes feed on common

prey such as mice and rabbits.

Symbol: -/- Symbol: -/-

• Elephants fight each other so that the dominant elephant will get to breed with the female (intraspecific competition – within a species)

• Barnacles competing for space on rocks

• Frogs and lizards compete for the same insects (interspecific competition – among different species)

• Trees compete for light in the forest

CompetitionExamples

2. Predation

• One predator eats and kills its prey.

• Example: lynx catch, kill, and eat snowshoe hare.

Symbol: +/- Symbol: +/-

Predation Examples

• Leopard killing a buschbock (gazelle)

• Venus fly trap – traps and digests flies

• Gypsy moths eat leaves• Baleen whales eat plankton

3. Mutualism

• Mutualism occurs when two individuals benefit each other

• Example: a bee and a flower, seed dispersal by animals, cleaner fish

Symbol: +/+ Symbol: +/+

Mutualism Examples

• Red-billed oxpecker eats insects on impala

• Clownfish live among anemones

• “Devil’s Garden”: ants poison all the plants except a single species –fending off competition and herbivory. The tree provides hollow stems for the ants to live in.

http://en.wikipedia.org/wiki/File:Impala_mutualim_with_birds_wide.jpg

4. Commensalism

• Commensalism occurs when one individual benefits, the other one neither benefits nor is harmed

• Example: Barnacles live on humpback whales but feed on other organisms in the water; birds building nests in trees.

Symbol: +/0 Symbol: +/0

Commensalism Examples

• Orchids and mosses make their homes on tree trunks

• Cattle egrets forage in fields with livestock

5. Parasitism

• Parasitism is when one individual lives on or in a host organism and feeds on it

• Parasites are generally smaller than their hosts

• Example: tapeworms are parasites of lynxes and wolves.

Symbol: +/- Symbol: +/-

Parasitism Examples

• Botfly larvae are internalparasites of small mammals• Strangler figs are parasites of trees• Heartworms are parasites of dogs• Cowbirds have a form of nest

parasitism

https://en.wikipedia.org/wiki/File:Eastern_Phoebe-nest-Brown-headed-Cowbird-egg.jpg

Summary Table

Type of Interaction Sign EffectsCompetition -/- Both species affected negatively

Predation +/- One species benefits, one species dies

Mutualism +/+ Both species benefit

Commensalism +/0 One species benefits, one is unaffected

Parasitism +/- One species benefits, one species is disadvantaged

Practice!

Classify each of these species interactions based on its description:•flatworms live attached to the gills of horseshoe crabs obtaining bits of food from the crabs’ meals. The crabs are unaffected.

Practice!

Classify each of these species interactions based on its description:•Lichens found on tree bark consist of algae and a fungus. The fungus obtains food from photosynthesis of the algae and the algae has a place to live.

Practice!

Classify each of these species interactions based on its description:•A flea feeds on the blood of a ground squirrel.

Practice!

Classify each of these species interactions based on its description:•Both bluebirds and starlings are cavity nesters (nest in holes in trees, poles, and fence posts). Neither species is able to dig holes. Both must rely on holes that already exist.

Practice!

Classify each of these species interactions based on its description:•A wood turtle lays its eggs on sand or gravel-sand beaches and banks along streams. A raccoon eats the turtle’s eggs.

Homework:

• p.55 # 1,7,8