5.1 What Is An Ecosystem

Question 1

Biosphere

Answer 1

The part of the Earth inhabited by living organisms, including the land, the oceans and the lower part of the atmosphere.

Question 2

Abiotic

Answer 2

An ecological factor that is part of the non-living or physical environment of an organism. Abiotic factors include climatic features (such as rainfall and temperature), solar energy input and edaphic factors. Edaphic factors relate to the soil.

Question 3

Biotic

Answer 3

An ecological factor that is part of the living environment of an organism. Biotic factors are determined by living organisms and include predation and competition. Biotic factors are usually density-dependent as their effects are related to the population density of the organism concerned.
Includes disease

Question 4

Predation

Answer 4

Predator An organism that feeds on another organism, killing it before eating it. Most familiar examples of predators, such as foxes and ladybirds, are animals and they usually prey on other animals. However, the term is sometimes used to describe animals that feed on plants, and carnivorous plants that feed on animals.

Question 5

Competition

Answer 5

Compete A relationship between different organisms that require the same resources. Interspecific competition occurs between different species. Weeds, for example, compete with crop plants for resources such as water, mineral ions and light. Intraspecific competition occurs between organisms of the same species, such as when seedlings of a particular species of plant compete with each other when they are growing close together.

Question 6

Photosynthesis

Answer 6

Photosynthesis, Photosynthesise
The process by which plants and certain other organisms are
able to convert carbon dioxide into carbohydrates using light energy. Although photosynthesis can be summarised in a simple equation: carbon dioxide + water > glucose + oxygen, it is a much more complex process consisting of two sets of reactions, the light- dependent reactions and the light-independent reactions.

Question 7

Habitats

Answer 7

Habitat The particular place where a community of organisms is found. Peat bogs, coral reefs and cultivated fields are all habitats for particular communities of organisms.

Question 8

Population

Answer 8

A group of individuals belonging to one species. Members of a population are generally found in one place at a particular time and are able to breed with one another. Daisy plants on a sports field or frogs in a pond are examples of populations.

Question 9

Community

Answer 9

All the living organisms – animals, plants and microorganisms – found in a particular place at a particular time. The community found on a coral reef, for example, consists of the corals themselves and the algae that live within their cells, together with all the other different species of animals – the fish and worms and crabs – as well as the bacteria.

Question 10

Niche

Answer 10

A description of the precise role of an organism in its environment. In simple terms, an organism’s niche is where it lives and what it does there. The niche of the two-spot ladybird would be described in terms of the abiotic aspects of its habitat such as the temperature range it can tolerate. A full description would also cover the biological aspects of its ecology such as the size of its aphid prey. An important biological principle is that no two different species have exactly the same ecological niche.

Question 11

Solar energy input

Answer 11

The amount of incident sunlight, that is, the amount of energy from sunlight reaching a given area of the Earth’s surface.

Question 12

Climate

Answer 12

All the weather-related conditions such as rainfall, wind exposure, and extremes of temperature make up the climate that affects an ecosystem.

Question 13

Topography

Answer 13

Characteristics of the physical
environment such as altitude, slope and aspect (direction land is facing)

Question 14

Ecosystem

Answer 14

An ecological term referring to all the organisms living in a particular area as well as the non-living features of their environment.

Question 15

Oxygen concentration

Answer 15

Oxygen availability The amount of oxygen, dissolved in water or otherwise, available for organisms (e.g. fish, invertebrates, bacteria).

Question 16

Edaphic

Answer 16

An ecological factor which is part of the abiotic or non-living environment of an organism and relates to the soil. Edaphic factors include soil pH, soil texture and mineral ion availability.

Question 17

Pollution

Answer 17

Damage to the environment through the presence of unnaturally large amounts of certain substances (e.g. carbon dioxide, oil, mercury), nearly always as a result of human activity.

Question 18

Catastrophes

Answer 18

A sudden and violent occurrence: earthquakes, floods, volcanic eruptions and fires are examples of catastrophes. These infrequent events affect the conditions in an ecosystem. These types of catastrophe are an abiotic (non- living) feature of the ecosystem.

Question 19

Competition

Answer 19

A relationship between different organisms that require the same resources. Interspecific competition occurs between different species. Weeds, for example, compete with crop plants for resources such as water, mineral ions and light. Intraspecific competition occurs between organisms of the same species, such as when seedlings of a particular species of plant compete with each other when they are growing close together.

Question 20

Interspecific

Answer 20

Between different species. Interspecific competition is competition between different species of organism. Weeds compete interspecifically with crop plants for resources such as water, light and mineral ions. Interspecific hybrids are made by crossing two species. For example, wheat and rye are two different species of cereal. Plant breeders have crossed these two species to produce an interspecific hybrid called triticale. Triticale combines the high quality and yield of wheat with the resistance to fungal infection of rye.

Question 21

Intraspecific

Answer 21

Between members of the same species. Intraspecific competition is competition between members of the same species of organism. Wheat plants growing in a field compete intraspecifically with each other for resources such as water, light and mineral ions.

Question 22

Grazing

Answer 22

A form of predation where the predator consumes part or all of a plant or other immobile organism. Usually applied to predation of plants by herbivores, but can apply to grazing of bacterial or algal lawns, or immobile animals, e.g. corals.

Question 23

Predation

Answer 23

Predator An organism that feeds on another organism, killing it before eating it. Most familiar examples of predators, such as foxes and ladybirds, are animals and they usually prey on other animals. However, the term is sometimes used to describe animals that feed on plants, and carnivorous plants that feed on animals.

Question 24

Parasite

Answer 24

An organism that lives in or on a host organism. The parasite gains an advantage from this relationship while the host suffers a disadvantage. Parasites of humans include malarial parasites and tapeworms, bacteria such as those which cause food poisoning, and viruses such the genital wart virus. Witchweed is a parasitic weed that infects crops such as maize in Africa.

Question 25

Mutualism

Answer 25

Relationship between two different organisms which is to the benefit of both.

Question 26

Density dependent

Answer 26

An ecological factor whose effects are related to the population density of the organism concerned is said to be density dependent. Biotic factors such as grazing, predation and competition are density dependent. The larger the population of rabbits in a particular area, for example, the greater the competition for food.

Question 27

Anthropogenic factors

Answer 27

Ecological factor arising from human activity that affects the organisms living in an ecosystem. Anthropogenic factors may be abiotic or biotic.

Question 28

How is the distribution of organism in a habitat affected?

Answer 28

that the numbers and distribution of organisms in a habitat are controlled by biotic and abiotic factors.

Question 29

How does the concept of niche accounts for distribution and abundance of organisms in a habitat.

Answer 29

A species niche will affect distribution because a species will only be located in an area that matches its niche.

Question 30

Herbivore

Answer 30

An organism that feeds on plants or other photosynthesising organisms. Cattle, sheep and rabbits are herbivores, so are seed-eating birds such as sparrows, and invertebrates such as butterflies and snails.

Question 31

Succession

Answer 31

The ecological process in which one community progressively changes into another. The first organisms to colonise bare rock, for example, are algae and lichens. They are the only organisms which can survive in the demanding conditions. These pioneers start to break up the rock surface allowing organic material to accumulate and soil to form. In this way they change the habitat and make it suitable for other species.

Question 32

Primary succession

Answer 32

Succession is the change of one community of organisms into another. A primary succession is a succession that starts in a place where there has not been a community before. Successions that start on bare rock or sand, or in open water are examples of primary successions.

Question 33

Pioneer species

Answer 33

The first organisms to colonise a newly formed habitat or a habitat which has been cleared of vegetation. On bare rock, for example, the pioneer species are algae and lichens. They are the only organisms that can survive in the demanding conditions. These pioneer species start to break up the rock surface allowing organic material to accumulate and soil to form. In this way they change the habitat and make it suitable for other species.

Question 34

Climax community

Answer 34

The different species of organisms that make up the final stage of an ecological succession. The nature of the climax community depends on environmental conditions such as the climate. In Britain, the climax community below approximately 500 metres is woodland, often dominated by oak.

Question 35

Secondary succession

Answer 35

Succession is the change of one community into another. A secondary succession is a succession which starts where an existing community has been cleared. Successions that start after fires are examples of secondary successions.

Question 36

Deflected succession

Answer 36

Succession is the change of one community into another. A community which remains stable only because of human activity is called a deflected succession. In Britain, succession would normally result in lowland grassland changing to woodland. The keeping of sheep on such ground prevents woodland developing. Grazing results in deflected succession.