Chapter Seven - Ecology

Question 1

What is community?

Answer 1

The relationships between all the living species in that area

Question 2

What is an ecosystem?

Answer 2

The relationship between all living species in their environment

Question 3

What is an environment?

Answer 3

The surroundings in which an organism lives

Question 4

What is a habitat?

Answer 4

The place where each organism lives and breeds

Question 5

What is population?

Answer 5

The number of organisms of a single species in a given habitat

Question 6

Give an overview of how to study the environment?

Answer 6

A range of sampling techniques can be used. Some techniques use apparatus that can be used to measure biotic (living) data, e.g. Distribution of plant or animal species.

Question 7

What is a pitfall trap? How is it used?

Answer 7

A jar or pot is sunk in a hole in the ground, stones are placed above to prevent rain flooding the trap or birds or other predators from removing trapped animals

How to use - a hole is dug to accommodate a container and a raised lid is places on top to prevent entry of rain/predators. The trap is then left for a period of time (e.g 24 hours). Useful for collecting small ground-living animals such as beetles.

Question 8

What is a quadrat?

Answer 8

Square frame of sides 1m or 50cm that can be placed at a series of randomly chosen coordinates. The abundance of plant species is often measured in this way - if individual plants can’t be identified (grass) then percentage cover can be used.

Question 9

What is a pooter?

Answer 9

Allows small animals to be sucked into an observation chamber so they can more easily be identified

Question 10

What are abiotic factors?

Answer 10

To understand an ecosystem fully, the abiotic (non-living) factors in the environment must be measured.
Includes
1. light intensity - light meter to measure
2. Temperature - thermometer
3. Wind speed - anemometer
4. Water availability - rain gauge
5. pH - pH meter or soil testing kit
6. Extent of cultivation
Also - space, shelter, predators, mineral availability

Question 11

Features of classifications of organisms you must know;

Answer 11

1. Chordates - animals with backbones: mammals, reptiles, fish amphibians, birds MRFAB
2. Insects - animals with an exoskeleton and body divided into three sections (head, thorax, abdomen) two pairs of wings, three pairs of jointed legs, body temp not constant
3. Annelids - animals with a segmented body and hairlike structures called chaetae for grip, body temp not constant
4. Flowering plants - plants with true roots, stems and a highly developed transport (vascular) system. Rely on flower, seed and fruit production to facilitate reproduction.

Question 12

The five kingdoms of organisms

For each state; group, nutrition, cell wall and cellular organisation

Answer 12

Protoctista
Nutrition - saprophytic or photosynthetic
Cell wall - cellulose / no cell wall
Cellular organisation - single-called sigh nucleus/ algae that are not truly multicellular

Bacteria
Nutrition - saprophytic
Cell wall - non-cellulose
Cellular organisation - single celled, lacking nucleus

Fungi
Nutrition - saprophytic or parasitic
Cell wall - non-cellulose
Cellular organisation - single or multicellular, sometimes difficult to distinguish cells and so are referred to as acellular

Plants
Nutrition - photosynthetic
Cell wall - cellulose
Cellular organisation - multicellular

Animals
Nutrition - heterotrophic
Cell wall - none
Cellular organisation - multicellular

Question 13

Explain the characteristics of protoctista

Answer 13

It is a kingdom containing organisms hard to classify e.g some contain plant and animal characteristics

Question 14

What is saprophytic nutrition?

Answer 14

A form of external digestion - enzymes act outside the organism and the products of digestion are then absorbed

Question 15

Why do viruses pose a problem for biologists?

Answer 15

They can only reproduce through invading host cells. For this reason they are hard to classify as true living organisms

Question 16

How are similar species classified into different species?

Answer 16

If they can breed to produce fertile offspring and look similar then they are the same species. E.g a horse and a donkey look very similar and can breed to produce a mule but mules are infertile so therefore horses and donkeys are different species.

Question 17

1. Population equation

2. Equation if immigration is not involved

Answer 17

Change in population size = (birth rate + immigration) - (death rate + emigration)

2. • No pop. Change - birth rate = death rate
     - pop. decrease - birth rate < death rare
     - pop. increase - birth rate > death rate

Question 18

Explain transfer of energy.

Answer 18

As plants are capable of photosynthesis they are able to harness the Suns energy and use this to produce food for themselves and other organisms that consume them. The flow of energy to plants can be represented in food chains.

Question 19

Give a food chain with examples and definitions

Answer 19

Tropic level 1–>tropic level 2–>tropic level 3–>tropic level 4
Producers> primary consumers>2nary consumers>tertiary c.
Plant ——> caterpillar ——> bird —-> bird of prey

Producers - make food by photosynthesis

Consumers - feed on other living things

Question 20

What is a pyramid of numbers?

Answer 20

A simple diagram used to represent numbers of organisms at each tropic level. It is common that numbers decrease as the food chain progresses from producer to tertiary consumer.

Question 21

Why would an atypical pyramid of numbers occur?

Answer 21

As one producer could provide food for many primary consumers. E.g. A single rose bush can sustain hundreds of aphids - greenflies.

Question 22

What is a pyramid of biomass?

Answer 22

A diagram used to represent the mass of living material at each trophic level. The steps of the pyramid always become shorter as you progress through the food chain.

Question 23

Guidelines for drawing a pyramid of biomass

Answer 23

• never change the order of the food chain - the producer is always at the bottom and the final consumer at the top
• keep it symmetrical
• bars should all have the same depth
• if required ensure you have an appropriate scale for the length of bars
• if converting from an atypical period of numbers to a pyramid of biomass remember pyramids of biomass are always proper pyramids

Question 24

Why are food chains are so short?

Answer 24

Food chains never exceed four or five levels because not all energy from one trophic level is transferred to the next. Reasons for this are:

• respiration of organisms at each stage releases heat energy that cannot be passed through feeding
• excreted waste contains some energy
• faeces also contains energy that cannot be digested
• not all parts of an organism can be eaten

Question 25

Why might countries suffering from famine only have one consumer?

Answer 25

Less chance for energy to be lost

E.g rice –> human

Question 26

Explain the process of decomposition

Answer 26

A key process in the recycling of carbon and nitrogen. The decay process releases the nutrients back into the soil. The bacteria and fungi responsible for this recycling feed on dead plant and animal material as well as waste materials released by egestion and excretion of animals.

Question 27

What is biodiversity?

Answer 27

A measure of the range of different species of organisms living in an area

Question 28

What is humus?

Answer 28

The result of decomposition. It is a component of the soil in which plants grow and from which they extract minerals. For this to happen, the bacteria and fungi involved release digestive enzymes on to the material. Following this extracellular digestion (meaning outside the body or cell) the soluble products are absorbed by the organism.

Question 29

Draw a diagram of the carbon cycle.

Answer 29

Carbon cycle diagram in page 45 of revision guide.

Question 30

Explain the carbon cycle.

Answer 30

The amount of c02 in our atmosphere should stay constant but if the amount of respiration and combustion of fossil fuels increases and the amount of photosynthesis decreases (due to deforestation for example) then levels of c02 will increase.

Question 31

Why have carbon dioxide levels increased?

Answer 31

There is a vast amount of scientific research to suggest that human activities have resulted in increased c02 levels which have in turn led to the greenhouse gas effect and global warming.

Although there is much evidence to support this theory it should be remembered there are other possible explanations for some of the increase in global temps such as natural variations in temp due to solar activity

Question 32

What factors are monitored of global warming and what have governments done in response to increase in co2 levels?

Answer 32

Abiotic data used to monitor global warming includes c02 levels, extent and size of polar ice fields, ice density and sea levels.

Govts have put in place policies at national and local levels to reduce c02 emissions through placing a greater emphasis on use of renewable energy sources and changes in agricultural practises.

Question 33

Draw diagram of the nitrogen cycle including labels and explanations.

Answer 33

The nitrogen cycle diagram is on page 46 of revision guide.

1. Animals feed on plants and covert plant protein to animal protein.
   | - death and excretion
   | - decay bacteria and fungi break down dead plant and animals to
   | produce ammonia
   \/
2. Ammonia
   | - nitrifying bacteria convert ammonia to nitrate (in process called
   | nitrification) which can be absorbed by plants
   \/
3. Nitrate –>Denitrifying bacteria covert nitrates to nitrogen gas- denitrification occurs mainly in waterlogged soils –>4. Nitrogen in air
   3 & 4
   | | - nitrogen- fixing bacteria converts nitrogen gas to nitrates
   | | - nitrogen fixation takes place in root nodules of legumes, the
   V V plants use the nitrates for growth
4. Plants absorb nitrates and use them to make proteins–> 1.

Question 34

What three major minerals are required for healthy growth in plants and what do they do?

Answer 34

Magnesium - for making chlorophyll
Calcium - for the production of new cell walls
Nitrogen - in the from of nitrates for the formation of protein

Question 35

What are root hair cells?

Answer 35

These are cells with an extended cell wall that increases the surface area for effective absorption of minerals and water.

Question 36

Why do farmers use fertilisers?

Answer 36

To improve growth of their crops. Fertilisers can be natural of artificial and argue designed to increase the levels of minerals magnesium, calcium and nitrogen and other minerals.

Question 37

Give an overview of natural fertilisers.

Answer 37

E.g manure, compost

• low cost
• release nutrients throughout growing season and do not leach easily
• amount of minerals contained in them vary
• they can be difficult to store and spread

Question 38

Give an overview of artificial fertilisers.

Answer 38

• more expensive than natural fertilisers
• more easily applied to fields
• more accurate level of each mineral can be applied
• soluble and can leach easily leading to pollution
• for food to be labelled organic, only natural fertilisers can be used during growing

Question 39

Explain mineral absorption.

Answer 39

The absorption of minerals from the soil relies on a process called active uptake. This process uses energy to move the minerals from low concentration to high concentration (against the concentration gradient).

Energy required for active uptake is derived from respiration - oxygen is required. If soil becomes waterlogged oxygen levels are too low goal low sufficient energy to be released. Results in minerals are not being absorbed and poor plant growth.

Question 40

What is eutrophication?

Answer 40

A form of water pollution and can be the result of sewage entering water ways. It’s a problem associated with incorrect use of fertilisers.

Question 41

Draw diagram of results of eutrophication

Answer 41

Additional nutrients to water from sewage, slurry and fertilisers run-off.
|
V
Leads to increased aquatic plant and algal growth. Many die due to shading
|
V
When algae die they are decomposed by bacteria
|
V
The bacteria use up the oxygen in the water
|
V
Fish and other animals die without oxygen

Question 42

Draw diagram summarising acid rain

Answer 42

Combustion of fossil fuels
V
Sulphur dioxide released
V
Sulfur dioxide dissolves in water vapour forming sulphuric acid
V
Water vapour forms clouds that are carried long distances
V
When rain falls it can cause a range of problems
V V V
- river and lakes become acidic, can lead to fish poisoning
- trees can lose their leaves (defoliation) and therefore die
- stonework (statues and buildings) can be corroded

Question 43

Where are the effects of acid rain seen? What is being done

Answer 43

The problems caused by acid rain are often not seen in the country that released the original pollutant as prevailing winds carry the rain clouds long distances before the rain falls.

International action is being taken to filter emissions from combustion of fuels and the increased used of renewable energy sources such as wind, solar and hydroelectric power has vastly reduced emissions of gases that cause acid rain.

Question 44

How is environmental change best monitored by biologists?

Answer 44

Indicator species
1. Lichen - simple plants that cannot tolerate air pollution. Their presence on brick, stone and roofing indicates low levels of pollution. They are rarely found in towns and cities where air pollution is high

2. Bloodworms - water-dwelling animals that can only survive when oxygen levels are low. They are therefore good indicators of instances of eutrophication