unit 4 revision

31
UNIT 4 REVISION

Upload: phil

Post on 24-Feb-2016

58 views

Category:

Documents


0 download

DESCRIPTION

Unit 4 revision. Chapter 1 - Populations. Define the following words: Ecosystem All the interacting biotic (living) and abiotic (non-living) features in a specific area. Population A group of individuals of the same species in a habitat Community - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Unit 4 revision

UNIT 4 REVISION

Page 2: Unit 4 revision

Chapter 1 - PopulationsDefine the following words:• Ecosystem• All the interacting biotic (living) and abiotic (non-living) features in

a specific area. • Population• A group of individuals of the same species in a habitat• Community• The organisms of all species that live in the same area• Habitat• The place where an organism normally lives• Niche• All the conditions and resources required for an organism to

survive and reproduce (its ‘role’)

Page 3: Unit 4 revision

Chapter 1 – Investigating Populations• List 3 factors to consider when using a quadrat• Size of quadrat, the number of quadrats to record, the

position of each quadrat• How can you get a random sample?• Create a grid on the area (lay out 2 long tape measures)

and obtain a series of co-ordinates using a random number generator and sample at each of those co-ordinates.

• How can we measure abundance?• Frequency – if a species is in 15 out of 30 quadrats then

its frequency is 50%. Percentage Cover – estimate the area within each quadrat that the species covers.

Page 4: Unit 4 revision

Chapter 1 – Investigating Populations• Explain the mark-release-recapture technique and how you

can use it to calculate an estimated population size1. A set of animals are caught and then marked in some

way.2. They’re then released back into the community.3. After a specified length of time, the community is revisited

and the same number or individuals is caught again. 4. The number of marked individuals is counted.

Estimated pop. = (Total number of individuals in the first sample x size Total number of individuals in the second sample)

number of marked individuals recaptured

Page 5: Unit 4 revision

Chapter 1 – Population SizeExplain how the following factors affect population size:pH:

light:

temperature:

water and humidity:

Label and explain the stages of the population growth curve:

Slow growth

Rapid growth

Stable, no growth

Slow growth – initially the small number of individuals reproduce slowly to build up numbers.Rapid growth – the ever-increasing number of individuals continue to reproduce rapidly. Stable state – factors limit the size of the population, e.g. food, predation

Affects enzymes. Populations are larger in areas of optimum pH.

Increasing light intensity increases photosynthesis, meaning faster plant growth and more food for animals.

Affects enzymes. Slow action at low temps, denaturation at high temps. Warm-blooded animals have to spend more energy keeping warm if the temp is too low, so a smaller pop size.

If water is scarce then populations are small. Humidity affects transpiration and evaporation.

Page 6: Unit 4 revision

Chapter 1 – Competition and Predation• What is intraspecific competition?• Competition between members of the same species• What is interspecific competition?• Competition between members of different species

Explain the predator-prey graph• When there are higher numbers of prey

the predators have more food. • This increases the numbers of

predators.• As there are more predators they eat

more prey.• This reduces the numbers of prey.• With less prey available the predators

have less food.• This reduces predator numbers. • With less predators the prey numbers

can increase again.

Page 7: Unit 4 revision

Chapter 1 – Human PopulationsUse the graphs to helpyou explain:Stable population:

Increasing population:

Decreasing population:

Explain the following factors that affect human population, and how they are calculated:Migration:

Birth rate:

Death rate:

Immigration – individuals join a population from outsideEmigration – individuals leave a population

Affected by economic conditions, cultural and religious backgrounds, social pressures and conditions, birth control, political factors.Birth Rate = number of births per year x 1000

total population in the same year

Affected by age profile, life expectancy, food supply, safe drinking water, medical care, natural disasters, war.Death Rate = number of deaths per year x 1000

total population in the same year

Birth and death rates are in balance. No change in population size.

High birth rate and fewer older people.

Lower birth rate and a lower death rate, so more elderly people.

Page 8: Unit 4 revision

Chapter 2 - ATP• Why do organisms need energy?• Metabolism, movement, active transport, maintenance, repair and division

of cells, production of substances, maintenance of body temperature• How does ATP store energy? • ATP has 3 phosphate groups. The bonds between these groups are

unstable and have a low activation energy. They break easily and when they do, they release energy.

• How is ATP synthesised?• Adding a phosphate to ADP. Via photophosphorylation (in photosynthesis),

oxidative phosphorylation (in the electron transport chain) and substrate-level phosphorylation (in glycolysis).

• Why is ATP a good immediate energy source?• It cannot be stored, but is rapidly re-formed. It releases energy in small,

manageable amounts. The hydrolysis of ATP is a single reaction, releasing immediate energy.

Page 9: Unit 4 revision

Chapter 3 – The Light Dependent ReactionWhat do plants capture light energy for?1. Making ATP

• Chlorophyll absorbs light energy and excites a pair of e-s• e-s leave the chlorophyll and are passed along a series of

carriers (redox reactions) in the membrane of the thylakoids• e-s lose energy at each stage• This energy is used to combine ADP + Pi ATP

2. Photolysis of water• Chlorophyll is now short of e-s• Water provides replacement e-s from water molecules that are

split using light energy• 2H2O 4H+ + 4e- + O2

• H+ ions are taken up by NADP, which becomes reduced NADP

Page 10: Unit 4 revision

Chapter 3 - The Light Independent Reaction

CO2

RuBP

2x TP

2x GP

ATP

ADP + Pi

Reduced NADPNADP

ATP

ADP + Pi

Glucose etc.

= a product from the light dependent reaction

Explain the Calvin Cycle

Page 11: Unit 4 revision

Chapter 3 - Factors Affecting Photosynthesis

What is a limiting factor?• The rate of a process is limited by the factor that is at its least favourable value

Limiting factors in photosynthesis?• Light intensity• CO2 concentration• Temperature

Page 12: Unit 4 revision

Chapter 3 - Limiting Factor Graphs – What is happening here?

Light Intensity

Rate of Photosynthesis

Low [CO2]Low Temp

High [CO2]Low Temp

High [CO2]High Temp

Page 13: Unit 4 revision

Chapter 4 - Glycolysis• Where does glycolysis take place?• In the cytoplasm of cells• Describe the process of glycolysis

P P

P P

Glucose is phosphorylated (USES 2 ATP)

Glucose splits into 2x Triose Phosphate (TP)

NAD

Reduced NAD

2x ADP + Pi

2x ATP

2x ADP + Pi

2x ATP

NAD

Reduced NAD

Hydrogen is removed from TP and given to NAD to form reduced NAD

TP is converted into pyruvate. This generates 4x ATP

Page 14: Unit 4 revision

Chapter 4 – The Link Reaction• What are the products of glycolysis?• 2x ATP, 2x reduced NAD, 2x pyruvate• Where does the link reaction take place?• In the matrix of the mitochondria• What is the overall equation for the link reaction?

• Pyruvate + NAD + CoA acetyl CoA + reduced NAD + CO2

Page 15: Unit 4 revision

Chapter 4 - The Krebs Cycle

Acetyl CoA

6 carbon molecule

Combines with a 4C molecule4 carbon molecule

NAD

Reduced NAD

Carbon DioxideCarbon Dioxide

FAD

Reduced FAD

ATP

2H2H

Describe the Krebs Cycle

Page 16: Unit 4 revision

Chapter 4 – The Electron Transport Chain• Using the diagram, explain the stages of the ETC and

how ATP is generated

1 23

4

5

6

Page 17: Unit 4 revision

Chapter 4 – Anaerobic Respiration• If no oxygen is present which part(s) of respiration can

take place?• Glycolysis only (only generates small amounts of ATP)• What products does this leave you with?• Pyruvate and reduced NAD• What is the equation for how plants deal with these

products?• Pyruvate + reduced NAD Ethanol + CO2 + NAD• What is the equation for how animals deal with these

products?• Pyruvate + reduced NAD Lactate + NAD

Page 18: Unit 4 revision

Chapter 5 – Energy and EcosystemsExplain the following terms:Trophic level:

Food chain:

Food web:

Producer:

Consumer:

Decomposer:

Describe how energy enters an ecosystem:

Describe how energy is lost from the food chain:

Each stage in a food chain

Showing feeding relationships and transfer of energy

Linking together all the food chains in an area

An organism that manufactures organic substances by photosynthesis

An organism that obtains its energy by feeding on other organisms

An organism that breaks down dead plant/animal matter to release nutrients

Energy from the Sun is trapped by producers. Plants only convert 1-3% of the Sun’s energy into organic matter.

Not all the organism is eaten, some parts cannot be digested easily (e.g. cellulose), loss by excretion, loss by heat from respiration.

The efficiency of energy transfers is calculated using the following equation:

Calculate the energy efficiency for this example:Energy available after the transfer = 50kJm-2year-1

Energy available before the transfer = 250kJm-2year-1

(50/250) x 100 = 20%

Page 19: Unit 4 revision

Chapter 5 - PyramidsExplain what a pyramid of numbers is:

Explain the advantages of using a pyramid of numbers:

Explain the disadvantages of using a pyramid of numbers:

Explain what a pyramid of biomass is:

Explain the advantages of using a pyramid of biomass:

Explain the disadvantages of using a pyramid of biomass:

Explain what a pyramid of energy is:

Explain the advantages of using a pyramid of energy:

Explain the disadvantages of using a pyramid of energy:

A pyramid drawn with bar lengths proportional to the numbers of organisms present

Can be easy to be accurate in some food chains, simple to construct

No account is taken of size, some food chains are hard to represent accurately (e.g. if millions of insects living on one tree)

A pyramid drawn with bar lengths proportional to the mass of plants/animals

More reliable than using numbers, fresh mass is easy to assess

To get dry mass the organisms need to be killed and a sample may not be representative of the population, does not show seasonal differences

A pyramid drawn with bar lengths proportional to the energy stored in organisms

Most accurate representation, much more reliable

Collecting data for pyramids of energy can be difficult

Page 20: Unit 4 revision

Chapter 5 – Agricultural EcosystemsDescribe what an agricultural ecosystem is:

Describe what is meant by productivity and give the formula:

Complete the table to show how natural and agricultural ecosystems differ:

An ecosystem made up of domesticated animals/plants to produce food for human consumption. Attempts are made to keep energy losses low.

Productivity is the rate at which something is produced.Net productivity = gross productivity – respiratory losses

Natural Agricultural

Input of Energy

Rate of Productivity

Amount of Species Diversity

Amount of genetic diversity within a

species

Nutrient Recycling

Control of Populations

Point in Succession

Solar energy only

Solar energy + energy from food

Lower Higher

More Less

More Less

Natural recycling of nutrients

Limited recycling of nutrients, fertilisers used

Natural means e.g. climate, competition

Natural means and use of pesticides etc.

Natural climax community

Artificial community prevented from reaching climax

Page 21: Unit 4 revision

Chapter 5 - Pests• What are pests and pesticides?• Pests are organisms that compete with humans for food/space.

Pesticides are poisonous chemicals that kill pests.• State 4 features of an effective pesticide• Specific, biodegradable, cost-effective, will not accumulate• What is a biological control?• Using predators of a pest to control its numbers. It is specific but

slower and the predator may become a pest itself. • Explain what an integrated pest-control system is• A system that integrate all forms of pest control to try and keep the

pest at an acceptable level. It does not eradicate the pest. • How does controlling pests affect productivity?• Removing pests increases productivity e.g. weeds take nutrients from

crops, slowing growth, so removing these increases growth of crops.

Page 22: Unit 4 revision

Chapter 5 – Intensive Farming• Explain how rearing animals intensively increases the

efficiency of energy conservation• Movement is restricted so less energy used in muscle

contraction• The environment is kept warm, so less heat lost from the

body• Feeding is controlled to give animals the optimum

nutrients for growth• Predators are kept out so energy is not lost to another

organism• Selective breeding has produced varieties of animal that

are better at converting food eaten into body mass

Page 23: Unit 4 revision

Chapter 6 – The Carbon Cycle• Describe the carbon cycle

CO2 in the atmosphere

AnimalsPlants

Photosynthesis

Feeding

Respiration

Decomposers

Death

Decay

Fossil Fuels

Decay Prevented

Combustion

Page 24: Unit 4 revision

Chapter 6 – The Greenhouse EffectDescribe what the greenhouse effect is:

State the main greenhouse gasses and describe where they come from:

Describe what global warming is:

Explain the consequences of global warming:A natural process. Some radiation from the Sun

reaches the Earth’s surface and is reflected back as heat. Greenhouse gases trap this heat and keep it close to the Earth’s surface, keeping us warm.

CO2 – comes from human activities mainlyMethane – from decomposers or the intestines of primary consumers such as cattle

The rising of the Earth’s average temperature. Human activities have increased the CO2 levels in the atmosphere from 270ppm before the industrial revolution to 370ppm today, trapping more heat.

Melting of polar ice capsRise in sea level, causing floodingHigher temperatures and less rainfall could lead to crops failing and changes in the distribution of plantsGreater rainfall and storms in some areas would alter the distribution of plants and animals Life cycles of insects would alter, insects carrying diseases could spread northwards

Page 25: Unit 4 revision

Chapter 6 – The Nitrogen Cycle

N2 in the atmosphere

Plants

Nitrogen fixation by mutualistic bacteria

AnimalsFeeding

Decomposers

Death

Ammonium ions Ammonification

Nitrite ions

Nitrate ions

Nitrification

Nitrification

Absorption

Denitrification

Nitrogen fixation by free-living bacteria

Describe the Nitrogen Cycle

Page 26: Unit 4 revision

Chapter 6 - FertilisersExplain why fertilisers are needed in agricultural ecosystems:

Explain how natural and artificial fertilisers differ:

Explain how fertilisers increase productivity

All plants need mineral ions from the soil. Repeatedly using the same land for crops will remove these minerals from the soil. Fertilisers can replace them.

Natural = Dead and decaying remains of organisms and waste materials.Artificial = Mined from rock deposits and blended together to give the best balance of minerals (NPK).

Minerals are needed for growth e.g. Nitrogen is needed for proteins. Plants that have sufficient minerals grow quicker, taller and have bigger leaves.

Explain Eutrophication:

1. Leaching of fertilisers increases nitrate concentrations in lakes and rivers2. Nitrate is no longer limiting and so algae and plants grow very quickly3. Results in an ‘algal bloom’ across the top of the water4. This prevents light reaching the lower depths5. Plants below the surface die6. Decomposers grow quickly with lots of dead plants for food7. Decomposers use up the oxygen for respiration8. Fish etc die due to lack of oxygen9. With less competition anaerobic organisms increase quickly10. These anaerobic organisms further decompose dead material releasing toxic wastes, making the

water putrid.

Page 27: Unit 4 revision

Chapter 7 - Succession

Explain what changes occur in the variety of species that occupy an area over time:

Explain what is meant by the terms:succession:

climax community:

conservation:To start with there are very few species, and only those that can survive the hostile conditions (pioneer species). Gradually more species will colonise the area and conditions improve (plants die and nutrients added to the soil). These will gradually be larger plants and trees until the stable state is reached.

The changes in an ecosystem, over time, of the species that occupy it

The stable, final, community that exists in a balanced equilibrium

Management of the Earth’s natural resources in such a way that maximum use can be made of them in the future

Explain how you can conserve habitats by managing succession:

You can help to keep a community at a stage before the climax community. This will keep different species present that would be lost in the climax community. E.g. the moorland in the UK is kept from becoming deciduous woodland by burning heather and sheep grazing.

Page 28: Unit 4 revision

Chapter 8 - InheritanceExplain what is meant by the following key terms:Genotype:

Phenotype:

Allele:

Homozygous:

Heterozygous:

Dominant:

Recessive:

The genetic composition of an organism

The characteristics of an organism (often visible), resulting from its genotype and the environment

One form of a gene

When the alleles are the same for a particular gene

When the alleles are different for a particular gene

An allele that is always expressed in the phenotype

An allele that is only expressed in the phenotype when there is another identical allele

Monohybrid Crosses.Complete the cross for green and yellow plants. Green is dominant. Both parents are heterozygous. What is the probability of a yellow offspring?

G g

G

g

GG

Gg

Gg

gg

Probability of yellow offspring = ¼ or 25%

Page 29: Unit 4 revision

Chapter 8 – Sex Linkage and Co-dominanceSex LinkageWhat do we mean by sex linkage?

Why are sex-linked diseases more common in males?

Complete a cross to show the chances of a child having haemophilia from a female carrier and a normal male.

Co-dominanceWhat is co-dominance?

An example of co-dominance is in the snapdragon flower, which can be red, white or pink. Complete a cross for a red flower and a pink flower.

A gene carried on the X or Y chromosome

If recessive, males only need 1 copy of the allele to suffer the disease, females need 2.

XH Xh

XH

Y

XHXH XHXh

XHY XhY

25% of children suffer, but 50% of sons suffer

Both alleles are equally dominant and are both expressed in a phenotype

CR CR

CR

CW

CRCR CRCR

CRCW CRCW

50% of offspring are red, 50% are pink

Page 30: Unit 4 revision

Chapter 8 – Multiple Alleles and Hardy-Weinberg

Multiple AllelesWhat are multiple alleles?

An example of multiple alleles are blood groups in humans. Alleles = IA, IB, IO. IA and IB are co-dominant whilst IO is recessive to both. Complete a cross to show the offspring of a female with blood group O and a male who is blood group AB.

Hardy-WeinbergWhat is the Hardy-Weinberg equation?

What can it calculate?

State the assumptions of H-W

Work out, using the Hardy-Weinberg equation, the allele frequencies of cystic fibrosis, a recessive condition affecting the lungs. In a population of 15,000 people, 1 person suffers from the disease.

More than 2 possible alleles for a particular gene

IA IB

IO

IO

IAIO IBIO

IAIO IBIO

50% blood group A, 50% blood group B

p2 + 2pq + q2 = 1

The frequencies of alleles in a population

No mutations, isolated population, no selection, large population, mating is random.

Recessive, so the frequency of tt = 1/15000So, q2 = 1/15000 = 0.000067So, q = square root of 0.000067 = 0.0082p + q = 1.0So, 1.0 – q = pp = 1.0 – 0.0082 = 0.9918 (This is the frequency of allele T)

Page 31: Unit 4 revision

Chapter 8 – Selection and SpeciationExplain directional selection

Explain stabilising selection

Selection that favours individuals at one extreme. Often occurs when environmental conditions change. Phenotypes at one extreme may be more suited to the conditions and so survive and breed more, passing on their genes. Over time the mean will move in the direction of these individuals.

Selection that favours average individuals. Occurs if the environmental conditions are stable. Those individuals closest to the mean survive and breed more, passing on their genes. Phenotypes at the extremes will be eliminated.

What is speciation?

Explain how geographical isolation leads to speciation.

The evolution of new species from existing species

1. Populations become separated2. Therefore they stop interbreeding3. Selection pressures will be different in

different areas4. Allele frequencies will change in the

different populations5. Over time they become so different

that they can no longer interbreed