IB Ecology

Ecology

Study of how an organism interacts with its environment both living and nonliving

Biotic factors

Living factors in an ecosystem

Abiotic factors

Non-living factors in an ecosystem

Food chain

Pathway of energy transfer between organisms in an ecosystem

Food web

Shows all food chains in an ecosystem

Exponential growth

• Rapid growth

• J-shaped

Logistic growth

• At the carrying capacity there is 0 growth

• Density dependent factors cause the slowing of the population growth and ultimately causes the population growth to stop

• S-shaped growth

Carrying capacity

The maximum amount of individuals an ecosystem can sustain of a specific population

Plant distribution

Factors that affect the distribution of plants

Range

Temperature

Light

Soil pH

Salinity

Plant nutrients

Range

Where an organism can be found in nature

Temperature

How hot or cold

Light

Amount of brightness

Soil pH

How acidic or alkaline the soil is

Salinity

Concentration of dissolved salt in the water

Plant nutrients

Chemicals within the soil that a plant needs in order to live (nitrates and phosphates)

Wet biomass

Measures both mass of the organism and the mass of the water

Dry biomass

Measures only the mass of organism after all water has been removed

Biodiversity

The degree of variation of life forms within a given ecosystem, biome or an entire planet; consists of species richness and evenness; higher the biodiversity = healthier ecosystem

Species richness

Total number of species in an ecosystem

Species evenness

How close each of those populations are in size to each other

The Shannon-Weiner Index

• The Shannon-Weiner Index is used to measure biodiversity (H’)

  • The higher the value the higher the biodiversity

• H’ = -𝚺 Pi (ln Pi)

• Pi = proportion of individuals found in the population

• Range of S-W index usually between 1.5 and 3.5 and rarely surpasses 4.5

• Shannon-Weiner is typically used to aquatic ecosystems

• Takes into account richness and evenness

• Presence of a dominant species is less impactful

Simpson Index

• The Simpson Index also can be used to determine biodiversity

• Lower value means more diverse

• Can be used in either situation

• Simpson index is typically used for terrestrial ecosystems

• Richness better keep evenness constant

• Presence of a dominant species is more impactful

Alien Species

Organisms that have established themselves in an area where they are not normally found

Invasive Species

An alien species that disrupts the ecosystem by causing extinction in some of the native species; detrimental because there will be a less diverse ecosystem (can be alien in one spot and invasive in another)

Kudzu

• Invasive species in southeast U.S.

• Naturally found in China

• It blocks sunlight over native plant species

Eucalyptus

• Invasive in Hawaii

Snakehead

• Invasive throughout most of the U.S. 

• Native to Asia (Thailand)

• They eat all of the fish in a body of water (predators)

• They can survive outside of water → wriggle their way to other bodies of water and eat all the fish there

Zebra Mussel

• Native to Europe

• Invasive to most of the U.S. 

  • Started in the Great Lakes

• Invasive due to ballast water that transported planktonic larva

• Detrimental because they reproduce much faster than the native species

  • Taking all zooplankton out of the water and causing the natives to go extinct

• Zebra mussels constantly sticking to pipes and boats (everything) → huge economic impact on humans

Grey Squirrel

• Red squirrel native to the U.K.

• Forests with no red squirrels

• Grey squirrels were brought to the U.K. by humans

  • Native to east coast of North America

  • Brought by hunters because they were bored

  • Outcompetes the red squirrels for food and habitats

Biological Control

Using a natural predator to control an unwanted or invasive species

Risk Benefit Analysis

Process in which one determines the likelihood of benefit and detriment a species will cause when introduced into an ecosystem

Why do a risk benefit analysis?

• There is a risk when introducing a new organism to an ecosystem

• Scientist must do experiments to determine risk benefit analysis and make a decision

Ex:  

1. Mongoose did not eat rats

2. Mongooses are diurnal and rats are nocturnal

3. Mongooses ate the native Hawaiian birds and made them go extinct