Ecology

IB Biology

Ecology

• The study of living organisms in the natural environment, how they interact with one another and how the interact with their nonliving environment

Levels of organization

atoms

molecules

organelles

cells

organs

tissues

systems

organism

species

population

community

ecosystem

biosphere

ECOLOGY

Species

• A group of organisms that can reproduce and produce fully fertile offspring

Great White Pelican Pelecanus onocrotalus

Population

• A group of organism of the same species which live in the same habitat at the same time where they can freely interbreed

• Habitat: the environment in which a species normally lives or the location of a living organism

The black-veined white butterfly(Aporia crataegi) mating

Community

• All the populations of the different species living and interacting in the same ecosystem

7-spotted lady bird

(Adephagia septempunctata)

Bean aphids

(Aphis fabae)

Red ant

(Myrmica rubra)

Broom plant

(Cytisus scoparius)

Ecosystem

• Community (Biotic) interacting with environment (Abiotic )

Components of an Ecosystem• Biotic Factors: living or once living organisms• Abiotic Factors: nonliving factors that have an effect on living thingsExamples:- Water: organisms have water in their bodies (50-95%) and chemical

reactions need water to happen.- Soil: type of soil determines which plants and other organisms live in

that location- Light and Temperature: affect photosynthesis (plant growth is limited

to amount of sunlight)

Energy + CO2 + H2O → C6H12O6 + O2

Energy and Organisms• Autotrophs: organisms which can synthesize their own complex,

energy rich, organic molecules from simple inorganic molecules (e.g. green plants synthesis sugars from CO2 and H2O; bacteria in deep sea vents doing chemosynthesis) - PRODUCERS

• Heterotrophs: organisms who must obtain complex, energy rich, organic compounds form the bodies of other organisms (dead or alive).

– Ex: consumers and decomposers (saprotrophs and detritivores)

Decomposers• Detritivores: heterotrophic organisms who ingest dead organic matter.

(e.g. earthworms, woodlice, large scavengers). Ingest first, then digest.

• Saprotrophs: heterotrophic organisms who secrete digestive enzymes onto dead organism matter and absorb the digested material. (e.g. fungi, bacteria). Digest first, then absorb.

Earthworm(Lumbricus terrestris)

Chanterelle

(Cantherellus cibarius)

Consumers

• Omnivore: eats both plants and animals

• Carnivore: meat eater

• Herbivore: plant eater

Food Chains• Sequence of relationships

between trophic levels.

• Show the flow of energy from the SUN to the heterotrophs

• Trophic level: an organism’s feeding position in a food chain

• Producers: essential to every single food chain

Food Web• Shows the feeding relationships in a community. Arrows show the flow of

energy.

Read the article and generate a food web: http://ehp.niehs.nih.gov/members/2004/112-8/focus.html

Growth (new biomass)

CellularrespirationFeces

100 J

33 J

67 J

200 J

Plant materialeaten by caterpillar

How much is available to the caterpillar’s predator?

Energy and Nutrients

• Energy enters ecosystems as light and usually leaves as heat.

• Nutrients do not usually enter an ecosystem and must be RECYCLED. Nutrients include: carbon, nitrogen, phosphorus, magnesium...

The Carbon Cycle

The Nitrogen Cycle

Pyramids of Energy

Biomass

• Amount of dry matter in one organism• Each bar represents: dry weight of all organisms in one

trophic level

Trophic level Dry weight(g/m2)

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

1.5

11

37

809

Populations• Characteristics:

– Size: number of individuals at a certain time– Density: number of individuals in a certain space at a particular time– Spacing: clumped, uniform, random– Age Structure

• Pop. Change = (birth + immigration) – (death + emigration)

• Limiting factor: prevents the continuing growth of a population in an ecosystem– Can be: - water, air, light, food- diseases, competitors, predators, parasites

Population Growth

• Exponential Phase: population increases exponentially because the natality rate is higher than the mortality rate.

• Transitional phase: difference between natality and mortality rates are not as great, but natality is still higher so population continues to grow, but at a slower rate.

• Plateau phase: natality and mortality are equal so the population size stays constant.

• Carrying Capacity: the maximum population size that can be supported by the environment

The Greenhouse Effect• Light from the sun has short wavelengths and can pass through most of the

atmosphere.• This sunlight warms the earth which in turn emits long wave radiation.• This long wave radiation is bounced back by the greenhouse gases, such as carbon

dioxide, methane, water vapor, oxides of nitrogen and sulphur dioxide

The Greenhouse Effect

• Natural and essential to life• Human pollution is making it worse = causing global warming

– Oxides of nitrogen: industrial processes, burning fossil fuels, fertilizers

– Methane: cattle, waste disposal, natural gas leaks – CO2: burning fossil fuels

• Consequences:– Changes in climate = effects on the ecosystem– Extinction– Melting glaciers = rise in sea level– Increase in photosynthetic rates

Changes in atmospheric CO2

Precautionary Principle• Action should be taken to prevent harm even if there is not sufficient data

to prove that the activity will have severe consequences• If people want to do activities that may cause a change in the environment

they must prove first it won’t do harm

• We should take action now: reduce carbon emissions before it’s too late• Should people invest money to reduce carbon emissions if we are not

100% sure about the consequences of global warming?• More expensive to be eco-friendly• What should consumers do?

Arctic Ecosystems- North America, Greenland, Iceland, Norway, Russia- Example: polar bears/seals/algae affected- Loss of ice habitat - Increased success of pests/pathogens/mosquitoes- Increased decomposition- Expansion of temperate species/reduced range for arctic species- Rise in sea levels- Climate change- Disturbance of food chains- Melting of permafrost