Chapter 4 – Ecology

Learning Objectives:

1.4.1 - 1.4.4 Ecology,

Ecosystem, Biosphere,

Habitat

1.4.5 Environmental

Factors

1.4.6 Energy Flow

1.4.7 Niche

1.4.8 Nutrient

Recycling

1.4.9 Human Impact on

an Ecosystem

1.4.10.H Pyramid of

Numbers

1.4.11.H Ecological

Relationships

1.4.12.H Population

Dynamics

1. Define the terms; ecology, ecosystem, biosphere, habitat.

2. Name a range of ecosystems demonstrating diversity.

3. List examples of habitats.

4. Define and give examples of the following as applied to terrestrial (land) and

aquatic (water) environments: Abiotic, Biotic, Climatic and Edaphic factors

5. Name the sun as the primary source of energy.

6. Name feeding as the pathway of energy flow.

7. Present a grazing food chain and a food web.

8. Construct a pyramid of numbers and explain its use.

9. Explain the term: niche and give examples.

10. Define the term nutrient recycling (by organisms).

11. Outline and draw the Carbon Cycle.

12. Outline and draw the Nitrogen Cycle.

13. Define Pollution, state areas affected and mechanisms to control it.

14. Explain the difference between the terms pollutant and pollution.

15. Discuss the ecological impact of one human activity.

16. Define Conservation.

17. Outline any one practice of conservation from agriculture, forestry or fisheries.

18. State problems associated with waste management & disposal.

19. Explain the importance of waste minimisation.

20. Explain the role of micro-organisms in waste management and pollution control

21. Explain the limitation of their use

22. State two inferences that can be made regarding the shape of the pyramid. For

example large tree or parasites

23. Explain the energy loss shown in the pyramid.

24. Name factors that can control populations.

25. Define and give one example of the following factors:

Competition. Predation, Parasitism, Symbiosis

26. Outline the contributory factors or variables in the Predator/Prey Relationships

27. State the effects on the Human Population due to:

War, Famine, Contraception, Disease

Ecology - is the study of living organisms, their interactions with each other and their

environment

Biosphere – the part of the planet which contains living things.

Ecosystem - is a community of organisms and their interactions with their environment.

Large ecosystems include temperate deciduous forest, grassland, freshwater pond, seashore, hot

desert, tropical rain forest.

Need to study one ecosystem in detail

Environment Types

Terrestrial Environment is a land-based habitat. E.g.: Forest, Grassland, Desert.

Key environmental factors include biotic, abiotic, climatic and edaphic.

Aquatic Environments are water based habitats. E.g.: Ponds, Lakes, Oceans.

They face special problems compared to terrestrial environments.

Plants are limited to upper levels of water due to lack of light.

Plants and smaller animals can be carried away by strong currents.

Waves can physically damage plants and animals.

Most animals can survive in either salt or fresh water, if the salt concentration

changes it can damage them (osmoregulation).

Organisms must be able to extract oxygen from water. Pollution can reduce oxygen

levels.

Environmental factors affecting living organisms.

Abiotic factors

Altitude: (Height above sea level) Higher altitudes have more extreme weather

conditions which many trees and animals cannot live in.

Aspect: (Direction a slope faces) North-facing slopes are cooler and darker than

south-facing, more plants grow on south-facing slopes.

Currents: Plants and animals are washed away by strong currents, only those that can

attach can survive.

Biotic Factors

Community- is the populations of different species living and interacting with each other in the

same habitat

Population - a group of individuals of the same species living and breeding in the same habitat.

Habitat - the place where an organism lives and to which it is adapted.

Abiotic Factors are non-living factors.

Biotic Factors are living factors.

Food: The more food available the more animals that will survive to feed on them.

Competition: Plants compete for light and space, animals for food, shelter and mates.

Humans: Some humans set up conservation areas, others cause pollution or hunt.

Predation: Predators reduce the number of prey in an area.

Climatic Factors

Temperature: higher temperatures increase plant growth, colder slow it down and

cause hibernation of animals.

Rainfall: Some plants/animals are adapted to low rainfall but all need water to survive.

Wind: Helps spread pollen and seeds, however can cause damage and evaporates water.

Edaphic Factors

Soil pH: different plants prefer acidic, alkaline or neutral soils, the presence of

particular plants also affects which animals are present.

Mineral Content: Different soil types have different minerals that are required by

plants for photosynthesis and growth.

Air/Water content: The size of soil particles determines the levels of water and air

present, both are essential to plants.

Energy

The sun is the primary source of energy for our planet.

Light energy from the sun is converted to chemical energy in plants which is passed to animals

when they eat the plants.

Feeding allows energy to flow from one organism to another.

Energy moves in only one direction.

Feeding Relationships

Primary consumers: feed on producers. They include:

o Herbivores: plant eaters

o Decomposers: feed on dead plants

o Detritus feeders: feed on dead plants and animals

Secondary consumers: feed on primary consumers. They include:

o Carnivores: Meat eaters

Climatic Factors involves weather over a long period of time.

Edaphic Factors involve soil; its pH, moisture, mineral and air content.

Producers (Autotrophs): organisms that make their own food (plants carry out photosynthesis).

Consumers (Heterotrophs): organisms that take in food from another organism.

o Scavengers: Feed on dead animals

Tertiary/Top consumers: feed on secondary consumers. Can be called Top consumers.

o Organisms that feed on both plants and animals are omnivores.

Only about 10% of energy in each level gets passed onto the next consumer.

As the energy decreases from each consumer to the next this limits the length of the

food chain.

The first member is always a producer (green plant).

A Trophic Level is a feeding stage in a food chain.

- 1st trophic level = producer

- 2nd trophic level = primary consumer

- 3rd trophic level = secondary consumer

- 4th trophic level = tertiary consumer

They show the inter-feeding relationships in an ecosystem.

Two inferences/conclusions can be drawn from this pyramid;

o The number of organisms declines as you go up the pyramid, due to the large loss of

energy at each trophic level.

o Organisms body size usually increases as you go up the pyramid

Limitations

They do not take into account the size of the organisms.

One million microscopic plankton may be represented by the same sized

rectangle as a thousand beetles.

A grazing food chain is a sequence of organisms in which each one is eaten by the next member

in the chain.

A Food Web consists of two or more interlinked food chains.

A pyramid of numbers represents the number of organisms at each trophic level in a food chain.

One oak tree is represented by a narrow triangle.

I.E. Numbers cannot be drawn to scale on a pyramid of numbers, it is simply a

simple representation.

Inverted Pyramids involve large producers, where only one producer feeds many primary

consumers.

This includes what it eats, what it is eaten by and how it interacts with both its

environment and other organisms.

In order for most species to live in one habitat they must have different niches.

Populations

Many factors combine to increase or decrease the numbers of any given population in a

habitat.

These factors mainly effect birth rates and death rates of organisms.

4 key factors include; 1. Competition, 2. Predation, 3. Parasitism, 4. Symbiosis

Competition: Occurs when organisms actively struggle for a resource that is in short supply.

o As a consequence the number of organisms is reduced.

o Plants compete for light, space and water.

o Animals compete for food, water, shelter, mates and territory.

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

(Buttercups compete for water & space).

o Inter-specific competition occurs between members of different species. (Blackbirds

& Thrushes compete for insects & snails).

Two key types of competition include; Contest & Scramble

Contest Competition: An active physical contest between two individual organisms, resulting in

one organism getting the resource, while the other is left without.

An Ecological Niche is the functional role an organism plays in the community.

A Population comprises all the members of a species living in an area.

o Examples; Deer/Hares/Starling Fighting for territory or mates. Hawks compete for

prey. Foxes compete for rabbits.

Scramble Competition: Competition in which all of the competitors get some of the resource,

generally reducing population numbers.

o Example; Seedlings overcrowded in a seedbed compete for light, water, minerals and

space.

Predation

A Predator: An organism that catches kills & eats another organism.

Prey: The organism eaten by the predator.

o Examples; Rabbit & Fox

o Mouse & Owl

o Aphid & Ladybird

o Whelks & Muscles

Adaptations: Features/characteristics developed by organisms to make them better suited

for survival in a particular habitat.

o Adaptations in predators:

Hawks & birds of prey have excellent sight to locate small prey.

Foxes & dogs have excellent sense of smell.

Ladybirds have strong mouth parts to help digest aphids.

Cheetahs & other wild cats are extremely fast to outrun prey.

o Adaptations in prey:

Frogs, fish and many insects are camouflaged to make them hard to see.

Ladybirds contain large amounts of formic acid, to discourage predators eating

them.

Mice are fast and flexible to evade predators.

Parasitism

o Exoparasites (ecto) live outside the host.

Example: Fleas on a dog, Aphids on a rosebush, Leeches on a human

o Endoparasites live inside the host.

Example: Liver fluke in sheep & cattle, Potato blight on plants, Disease-causing

bacteria in humans

Parasites differ from predators because;

They are smaller than the host

They often attack from within

They are usually dependent on one individual host

They do small levels of damage to the host but don’t usually kill host thus don’t reduce

population numbers

Predation involves the catching, killing & eating of another organism.

Parasitism: involves 2 organisms of different species living in close association, where one

organism (parasite) benefits at the expense of the other (host).

Parasitism is a form of symbiosis in which only the parasite benefits but at the expense

of the host.

Mutualism involves a mutually beneficial relationship, where both benefit.

Intestinal bacteria; breakdown cellulose in the intestine & produce vitamins,

benefit from food, warmth and shelter

Lichens; (algae & fungus) algae get protection, minerals & support, fungi get food

Nitrogen-fixing bacteria in plants; Plant gets nitrates, bacteria get food, shelter

& anaerobic conditions

Population Dynamics

PREDATOR-PREY RELATIONSHIPS

Variables that contribute to this interaction include;

o Availability of Food: A large number of prey can cause an increase in the number of

predators. As the prey is killed off the number of prey declines, allowing the prey numbers

to increase again.

o Concealment: Prey can prevent themselves from being wiped out completely by

hiding/concealing themselves until predators relocate.

o Movement of Predators: When predators need to compete for smaller numbers of prey

they often choose to relocate to areas where prey are in larger numbers.

Human Populations

Human population growth has increased rapidly in recent centuries (increasing by ~ 85 million

each year, 230, 000 per day).

The increasing populations is not due to an increase in birth rates, but by a reduction in death

rates.

4 key factors affecting human population numbers are; War, Famine, Contraception, Disease

Symbiosis occurs when two organisms live in close association in which one or both benefit.

Population Dynamics refers to the factors that cause population numbers to change.

War

o War can drastically reduce populations due to high death rates, however effects are

usually short lived due to the increased birth rates that come after.

Famine

o Although first world countries are no longer affected, third world countries suffer

from vast shortages of food and water, resulting in large numbers of people dying due

to malnutrition and starvation. Advancements in agriculture are beginning to improve

this for many countries.

Contraception

o Increased education around and availability of contraception has reduced birth rates

since the 1960s.

Disease

o The advancements in modern day medicine have led to increased life spans. Vaccines

have reduced the incidences of diseases such as Cholera, TB, Polio & Typhoid. Surgery

methods and drug treatments have also improved.

Nutrient Recycling

Two keys elements recycled are Carbon and Nitrogen.

The Carbon Cycle involves converting carbon from the environment to carbon in living things.

1. Burning of fossil fuels releases carbon dioxide into the air.

2. Plants take in Carbon Dioxide from the environment and use it in photosynthesis.

3. Animals eat the plants and take in the carbon they contain.

4. Micro-organisms breakdown animal waste and dead plants and animals releasing carbon back

into the environment.

The Nitrogen Cycle involves taking nitrogen from the air and making it useable for living things.

Nutrient Recycling is the way in which elements are exchanged between the living and non-living

components of an ecosystem.

Nitrogen Fixation is the conversion of nitrogen gas into ammonia (NH3), ammonium (NH4+) or

nitrate (NO3-).

Nitrification is the conversion of ammonia and ammonium to compounds of nitrite and then nitrate.

Denitrification is the conversion of nitrates to nitrogen gas.

Nitrogen makes up 78% of the air around us.

They cannot use nitrogen as it is present in the air and must convert it into nitrates and other

usable forms.

o Nitrogen fixation is an anaerobic process carried out by bacteria on the nodules on

roots of legumes. It is a symbiotic (mutually beneficial) relationship between the

bacteria and legumes.

1. Nitrogen-fixing bacteria convert nitrogen in the air into nitrates.

2. Plants absorb and use these nitrates to make protein and DNA and RNA.

3. Animals then eat these plants and use the nitrates for the same purpose.

4. When plants and animals die, bacteria convert these decaying nitrates into ammonia.

5. Nitrifying bacteria then convert this ammonia into nitrites and then nitrates.

6. Some nitrates are reabsorbed by plants, some are denitrified by bacteria in the soil and re-

enter the atmosphere.

Pollution

Examples: Dumping, sewage disposal, burning of fossil fuels, transport, noise production,

radioactive processes, etc.

Pollutants are the substances that cause pollution.

Examples: Household waste, fertilisers, herbicides, slurry, silage effluent, rubbish, smoke,

aerosols, etc.

Effects of a Pollutant - Ozone

Ozone is a gas that protects the earth from UV radiation.

The Ozone layer is 10-45 km above the earth.

Depletion is resulting in holes forming and is caused by chemicals such as CFCs

(Chlorofluorocarbons), aerosols and Freon gas (fridges).

EFFECTS:

Ozone absorbs UV rays from the sun. Depletion means more UV can penetrate to the

earth’s surface.

Pollution involves causing harm to the environment.

This results in: Increased skin cancers, Damage to crops and plants, Damage to plankton so

reducing aquatic life.

CONTROL:

Reduce the use of CFCs

Replace CFCs with HFCs (breakdown faster)

Stop using aerosols that contain CFCs

Dispose of fridges safely

Ecological Impact of one Human Activity – Global Warming/Greenhouse Effect

Conservation

- Human activity constantly alters the environment we live in, it is important we reduce and

reverse the damage we do to our environment to prevent damage to and extinction of species.

- Examples of damage: use of fossil fuels, peat and gas, overfishing, deforestation, global

warming & destruction of habitats such as rainforests.

Why Conserve?

Prevents extinction of species

Protects vulnerable organisms

Maintains the balance of nature

Maintains biodiversity (variety)

Organisms may be useful in the future

Habitats are enjoyable to visit

It is unethical and irresponsible to destroy the world we live in for future generations

Example of Conservation – The Fishing Industry

The Fishing Industry suffers from many problems including:

1. Pollution of waterways resulting in reduced numbers of fish

2. Overfishing resulting in reduced fish numbers

The Fishing Industry has a number of practices in place to help conserve fish stocks including:

- Monitoring and analyses of water for pollution

Conservation is the wise management of our existing natural resources.

- Setting fishing quotas so stocks do not get depleted

- Setting size limits on net mesh to allow small fish escape

- Checking fish stocks regularly

-

- The most obvious way to do this is to recycle the waste.

- In households we can recycle our plastic, paper, cans and bottles.

AGRICULTURAL INDUSTRY – Waste Management

- There are main waste products from farms, the worst of which include: slurry, silage effluent

and fertilisers.

- These are often washed into rivers and lakes.

- Eutrophication is the addition of nutrients to fresh water resulting in a shortage of oxygen to

plants and fish causing them to die.

- By storing slurry and effluent in leak proof tanks and only spreading them on dry land we can

prevent this pollution.

FISHING INDUSTRY – Waste Management

- In fisheries the unwanted parts of fish (heads, tails, intestines, fins, blood, etc.) are highly

alkaline and cannot simply be dumped back into the water.

- They are neutralised by formic acid, pulped and dried and sold as fertilisers or pig feeds.

FORESTRY INDUSTRY – Waste Management

- In forestry tree stumps, tree tops, small branches and roots are all waste products.

- The small branches are spread onto the forest floor to help firm soft ground.

- Branches and stumps are allowed to rot naturally, this returns nutrients to the soil.

- Tree tops and larger branches are turned into sawdust and used to make MDF.

PROBLEMS with Waste Management

- Disease-causing microorganisms may be present and spread to drinking water or food sources.

- Toxic chemicals may be washed into water sources killing plants and animals.

- Eutrophication may occur resulting in loss of aquatic life.

- Waste in landfills can be unsightly and attract rats and seagulls.

- Incinerators release smoke and poisonous gases into the atmosphere.

CONTROL of Waste

Waste production can be easily managed using the three R’s.

Reduce: Use less, minimise waste

Reuse: Use again for a different purpose

Recycle: Change, recover some material, use again

Waste management involves the safe disposal of waste materials so as not to damage the

environment.

Micro-organisms – Importance of Waste Management

o In landfill sites, biodegradable rubbish is broken down over time by bacteria and fungi and

provides nutrients for the soil.

o Sewage and waste water enter treatment plants or septic tanks. The waste has bacteria

added which breaks down much of the organic matter reducing a build up of waste.

o Compost heaps involve bacteria and fungi breaking down the waste into what eventually forms

compost.