ECOLOGY

Chapter 4

Ecology

Ecology is the study of the interactions between living things and their environment.

The Biosphere

The biosphere is the part of the planet (air, water, soil) in which life is found.

Population

A population is all the members of the same species in an area.

Community

A community contains many different populations in an area (animals, plants, fungi, micro-organisms).

Ecosystem

An Ecosystem is a group of clearly distinguished organisms that interact with their environment as a unit.

Habitat

A Habitat is the place in which an organism lives.

Examples: Hedgerow, Forest.

4 Environmental factors affecting distribution of organisms

1. Abiotic Facrors

2. Biotic Factors

3. Climatic Factors

4. Edaphic Factors

Abiotic Factors (Non-Living)

• Altitude

• Aspect

• Steepness

• Currents

• Exposure

Biotic Factors (Living)

• Food• Competition• Predation• Parasitism• Pollination• Seed Dispersal• Human activity

Climatic Factors (Long-term weather)

• Temperature• Rainfall• Humidity• Day length• Light intensity• Wind

Edaphic Factors (Soil)

• pH

• Particle size

• Organic matter

• Water/air/mineral content

Aquatic (Water) Habitats have several problems compared to terresterial habitats.

• Light may not penetrate

• Currents move organisms

• Wave action moves and damages organisms

• Salt content (salinity) means organisms adapt to freshwater or saltwater

• Oxygen is in lower concentration

The Sun is the main source of energy for the planet. Energy flows in one direction from the sun to producers to consumers.

• Producers are autotrophic (they make their own food).

• Primary consumers feed on producers. They are herbivores (plant eaters).

• Secondary and tertiary consumers feed on animals. They are carnivores (meat eaters)

A food chain

A food chain is a list of organisms in which each organism feeds on the next member.

A grazing food chain starts with a producer.

Each feeding stage is a trophic level.

Usually the number of organisms decrease as go move up a trophic level. A foodchain is limited in length by the loss of 90% of the energy at each trophic level.

Energy Flow – About 90% is lost at each link in a food chain.

The Pyramid of Numbers

A pyramid of numbers is a representation of the numbers of organisms at each trophic levels

A Food Web

A food web is a series of interlinked food chains

Niche

A niche is the role an organism plays in the community.

Organisms with identical niches will compete with each other.

Energy flows through the ecosystem, whereas nutrients (minerals) are recycled.

The carbon cycle and nitrogen cycle must be studied for this course.

In The Carbon Cycle

• Carbon dioxide is removed from the environment by photosynthesis in plants.

• Carbon dioxide is returned to the environment by:

• Respiration in plants, animals and micro-organisms.

• Decay caused by microorganisms.

• Combustion.• Weathering.

Role of micro-ogganisms in the Nitrogen Cycle

Type Location Acts on Product

Nitrogen fixingFree in Soil or in nodules in legumes

N2gas Nitrates (NO3)

Bacteria and Fungi of Decay

SoilDead organic matter

Nitrogenous waste (e.g. ammonia)

Nitrifying SoilNitrogenous waste (e.g. ammonia)

Nitrates

Denitrifying Soil Nitrates N2 gas

3 ways Humans affect ecosystems

Pollution

Waste Management

Conservation

Pollution

Pollution is any undesirable change in the environment caused by pollutants.

E.g. CFC’s cause ozone depleation.

C

D A

B

Say what A, B, C & D stand for in the nitrogen cycle? (20)

Ecological pyramids

Pyramid of numbers are limited because:

•The size of the organisms can change the standard shape.

•It may not be possible torepresent large numbers of organisms correctly.

•Include pyramids of numbers, mass or energy.

•Allow different communities to be compared according to different trophic levels.

•They indicate that the number of organisms falls as you ascend each pyramid.*

•The body size of the organisms increases as you ascend each pyramid.*

Population

A population is all the members of the same species in an area.

The factors that control the numbers in a population act mainly on the birth and death rates.

Factors controling population include competition, predation, parasitism and symbiosis.

Competition

Competition occurs when two or more organisms seek a scarce resource.

Intra-specific competition takes place between members of the same species.

Inter-specific compeittion takes place between different species.

Competition reduces population numbers

The 2 main types of competition are:

Contest Competition where one organism gets the resource while the second is left without.

Scramble Competition which means that all of those competing get some (but often not enough) of the resource.

Predation

Predation is the catching, killing and eating of another organism. A predator catches, kills and eats other organisms (prey

Predation initially increases the number of predators and decreases the number of prey.

The numbers of predators and prey often show repeated cycles of rising and falling numbers.

Parasitism

A parasite is an organism that feeds from and harms another organism.

Exo- or ectoparasites live on the outside of the host.

Endoparasities live inside the host.

Parasites sometimes reduce the numbers in a population, but often have little effect on the host numbers.

Symbiosis

Symbiosis (Mutualism) occurs when two organisms from a different species live in close association for the benefit of at least one of the organisms.

Population dynamics

Population dynamics refers to factors that cause changes in population numbers.

Predator-Prey numbers interact due to:

Availability of food, which increases predator numbers when high but reduces them when low

Concealment, which means that some prey survive by hiding from predators

Movement of predators, which means that move to new areas when prey numbers are low.