EcologyIB 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

The Niche Concept• Ecological niche-the unique role of a species within an

ecosystem• Spatial habitat• How the species obtains food• Interaction with other species

All of the above factors must be present in order for a species to reside in a particular area.

Types of Niches• Fundamental

• Potential mode of existence, given the adaptations of a species• Refers to the broadest range of habitats it can occupy and roles it

can fulfill

Types of Niches• Realized

• Actual mode of existence• Results from combination of adaptations and competition with

other species

Competitive Exclusion Principle

• Two species cannot survive indefinitely in the same habitat if their niches are identical

• One species will lead to the decline of another or both will narrow their niche to avoid competition.• This leads to realized niches.

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)

Interspecific Interactions• Competition:

• Occurs when two species require the same resource and the amount obtained by one species reduces the amount available for the other.

• Example: Red and grey squirrels• Compete for food in Britain where they occur together• Grey squirrels usually obtain much more food• Red squirrels disappear (or do they?)

Interspecific Interactions• Herbivory:

• Primary consumers feed on producers• Predation:

• Consumer feeding on another consumer• Parasitism:

• One organism feeds off another but does not kill that organism• Mutualism:

• Two species live in close association where both organisms benefit from the relationship

Keystone Species• A keystone species is one that has a disproportionate effect on

the structure of an ecological community.• Drastic changes usually occur when this species is removed.• Examples: Sea Star, Sea Otter, Elephant, Mountain Lion,

Prairie Dog (p. 612—IB)

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 things• Distribution of species is affected by limiting factors.

• Can be biotic or abioticExamples:- 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

Use of Transects• Transects are used to correlate distribution of plant or animal

species with an abiotic factor.• A transect is a method used to insure that there is no bias when a

scientist is sampling.

Types of Transects• Line transects

• Tape laid along ground• Sampling can be done by

recording all the organisms that touch the line or a distance from the line

Types of Transects• Belt Transect

• Sampling is carried out between two lines separated by a fixed distance

• Often done between two different types of environments

Types of Transects• Point Transect

• Researcher stands at a certain point and makes observation within a certain radius of that point

• Often used in bird studies

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 from 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.

http://commons.wikimedia.org/wiki/File:Nutrient_cycle.svg

Gersmehl diagrams were first developed in 1976, by P.F. Gersmehl, to show the differences in nutrient flow and storage between different ecosystems

Sinks for nutrient storage:• Biomass (flora and fauna)• Litter• Soil

http://commons.wikimedia.org/wiki/File:Nutrient_cycle.svg

Gersmehl diagrams were first developed in 1976, by P.F. Gersmehl, to show the differences in nutrient flow and storage between different ecosystems

Nutrient inputs into the ecosystem:• Nutrients dissolved in raindrops• Nutrients from weathered rock

Nutrient outputs (losses) from the ecosystem:• Nutrients lost through surface runoff• Nutrients lost through leaching

C.2.S3 Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores and flows between taiga, desert and tropical rainforest.

• Litter (pine needles) is the main store

• Slow rate of nutrient transfer between stores

• Soil is the main store• Slow rate of nutrient

transfer between stores (except for the transfer from biomass to litter)

• Biomass is the main store (soil is nutrient poor)

• Fast rate of nutrient transfer between stores

tagia(temperate forest)

desert

tropical rainforest

Image source: Allott, A. (2014). Biology: Course companion. S.l.: Oxford University Press.

C.2.U3 The percentage of ingested energy converted to biomass is dependent on the respiration rate.

Growth (new biomass)

CellularrespirationFeces

100 J

23 J

67 J

200 J

Plant materialeaten by caterpillar

How much is available to the caterpillar’s predator?

Biome is a geographical area that has a particular climate and sustains a specific community of plants and animals (i.e. a type of ecosystem)

Biosphere is the total of all areas where living things are found (i.e. the totality of biomes)

• The main factors affecting the distribution of biomes is temperature and rainfall• These factors will vary according to latitude and longitude, elevation and proximity to the sea• Temperature is influential because it affects the rate of metabolism – the phases in the life cycles

of many organisms are temperature dependent• In the same way, the availability of fresh water (both in the soil and in rivers and lakes) is critical to

the growth and nutrition of organisms• Rainfall and warmer temperatures are more common near the equator and less common at the

poles

Climate and Ecosystem Type• The type of stable ecosystem that will emerge in an area is based on

climate.• Climate is a property that emerges from the interaction of a number of

variables including temperature and precipitation.• Temperature and precipitation influence:

• Distribution of organisms• Rates of cell respiration• Productivity • Photosynthesis• Plant life• Decomposition rates

Six Major Biomes

Whitaker Climograph

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

Types of Ecosystems• Open systems: Matter and energy

freely flows with the environment• Closed system: energy ONLY flows

into and out of an environment

C.2.A2 Consideration of one example of how humans interfere with nutrient cycling.

Humans practices can accelerate the the flow of matter into and out of ecosystems. This by implication (and often design) alters the nutrient cycling in ecosystems.

Biomass (including

phosphates and nitrates)

removed from the

agricultural ecosystem

Phosphates and nitrates

removed from the

agricultural ecosystem and

added to adjacent aquatic

ecosystems

phosphates added to

the agricultural

ecosystem

phosphates added to

the agricultu

ral

ecosystem

Phosphate mined and

converted to fertiliser.

Nitrate fertiliser produced from

atmospheric Nitrogen

(by the Haber process)

Agriculture

Harvesting of crops

Water run-off (leaching) from

agricultural fields results in build-

up of phosphates and nitrates in waterways and

leads to eutrophication.

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

Biomagnification• Pollutants become concentrated in the tissues of organisms at

higher tropic levels.• Happens when toxins are fat-soluble and not easily excreted• Why does this happen?

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

Alien and Invasive Species• Introduced species that are not native to an area

• Endemic: species that are native to an area• Alien: human introduced species• Invasive: species that increase in number and spread rapidly

Why? Accidental; biological control; economic

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

A CREDIBLE Threat? Absolutely!

• Changes in arctic conditions (reduced permafrost, diminished sea ice cover, loss of tundra to coniferous forests)

• Rising sea levels • Expansion of temperate species increasing competition with native

species (e.g. red fox vs arctic fox)• Decomposition of detritus previously trapped in ice will significantly

increase greenhouse gas levels (potentially exacerbating temperature changes)

• Increased spread of pest species and pathogens (threatening local wildlife)

• Behavioral changes in native species (e.g. hibernation patterns of polar bears, migration of birds and fish, seasonal blooms of oceanic algae)

• Loss of habitat (e.g. early spring rains may wash away seal dens)• Extinction and resultant loss of biodiversity as food chains are disrupted