YEAR 10 LIFE SCIENCE EXAM Revision Solutions

TOP I C 1: GEN E T I CS ( C H A P T ER 1 A N D BO O K L E T )

1. How many chromosomes are in a human somatic (or non sex) cell? 46 chromosomes2. How many chromosomes are in a human gamete (sex cell)? 23 chromosomes3. Draw a diagram of a DNA strand labelling the following parts: Phosphate, Sugar, hydrogen bond, adenine,

thymine, cytosine and guanine.

4. What is dominant and recessive inheritance? Give an example of a dominant inheritance over a recessive.Dominant inheritance: Alleles inherited from parents that are represented in the phenotype and override the recessive genes eg brown hair overrides blonde hairRecessive inheritance: Alleles that are inherited from parents but don’t show through as a phenotype if a dominant gene is present (masked) eg blonde hair and blue eyes.

5. What is the difference between co-dominance and incomplete dominance inheritance?Co – dominance is the inheritance of two dominant alleles that are both represented in the phenotypeTOGETHER eg parent 1 homozygous dominant white mouse parent 2 homozygous dominant black mouse =offspring black and white mouse.Incomplete dominance is the inheritance of two dominant alleles that are BLENDED in the phenotype eg parent1 is a homozygous dominant black mouse parent 2 is a homozygous dominant white mouse = offspring grey mouse.

6. Name the 4 nitrogenous bases and show which bases pair up.Adenine + Thymine and Guanine + Cytosine

7. a) What is a mutation? An error that occurs in mitosisb) What is a mutagen? A factor that causes a mutation to occurc) Name 2 mutagens? UV rays, Chemicals, X-Raysd) Explain how a mutation can be an advantage or a disadvantage. Mutation can be beneficial to the organism

eg fly’s become resistant to fly spray overtime therefore extending their life. Disadvantage can cause disease.

8. What is the difference between a gene and chromosomal mutation? Gene Mutation: when a base is added, altered or deleted resulting in a change in the DNA structure Chromosomal Mutation: when a codon is added,altered or deleted resulting in a change in the DNA structure.

9. Discuss the differences between mitosis and meiosis by completing the following table:Meiosis Mitosis

Where does it occur Gametes Somatic cellsNumber of divisions 2 1Number of daughter cells produced 4 2Number of chromosomes in eachdaughter cell

23 46

Identical to parent cell? (yes or no) No Yes

10. Define the following terms:a. Phenotype A characteristic or trait expressed in the individual (such as blue eyes or brown hair)b. Genotype The combination of the 2 genes inherited for a particular characteristicc. Alleles Different forms of the same gene i.e. if you inherit brown eye gene and a blue eye gene –

they are classed as allelesd. Homozygous alleles for a particular trait are the same, there is no competition between these genes. e. Heterozygous alleles for a particular trait are different, one will override the other.f. Y chromosome a sex chromosome which is normally present only in male cells, which are designated

XY.g. X chromosome a sex chromosome which is normally present in male and female cells, which are

designated XY or XX.11. A heterozygous red fox mates with a homozygous silver fox. Red “R” coat colour in foxes is dominant to silver-

grey “r” coat. For each of the crosses shown below(i) Write the genotype of each parent Rr and rr(ii) Draw a Punnet square

R rr Rr rrr Rr rr

(iii) Write the genotypes of the offspring Rr or rr(iv) Write the percentage of each phenotype expected. 50% red and 50% grey

12. Red (CR) flowers crossed with a white flower (CW) produce pink flowers (CRCW). a. What is this type of inheritance called? Incomplete dominanceb. What offspring are produced when 2 pink flowers are crossed?

CR CWCR CRCR CRCWCW CRCW CWCW

25% red25% white50% pink

13. What are sex-linked genes? Genes or mutations located on the X or Y chromosomes14. Colour-blindness is a X-linked recessive trait. A woman, who is a carrier of colour-blindness, has children with a

man with normal vision. What is the chance of getting a colour-blind boy?XN Xn

XNXNXN XNXn

Y XNY XnY

50% chance of having a colour blind boy

15. Why do sex linked traits occur more often in males than females?Males do not have another X chromosome to override the bad Xchromosome

16. A typical pedigree for a family that carries Falconi anemia. Note that carriers are not indicated with half- collared shapes in this chart. Individuals affected are represented with the lines.

To answer questions #a-e, use the letter "f" to indicate the recessive Falconi anemia allele, and the letter "F" for the normal allele.

a. What is Arlene's genotype? ffb. What is George's genotype? Ffc. What are Ann & Michael's genotypes? Ann: Ff Michael: Ffd. Most likely, Sandra's genotype is FFe. List 2 people from the chart (other than George) who are most likely carriers of Falconi anemia.

Ann, Michael

T OP I C 2: P S Y C H OLO GY

1. What is psychology? Is the study of the brain and behaviours of living organisms2. List 2 fields a psychologist may specialise in? Child and Sport psychology3. What are the 2 main divisions of the nervous system? Central Nervous System and Peripheral Nervous System4. What are the 2 parts of the peripheral nervous system? How are these two different? Autonomic and Somatic

Nervous systemsAutonomic is the body’s functions that happen AUTOMATICALLY eg breathing and heart rate and the somaticnervous system can be controlled and decided upon by the individual eg muscle movemen

5. What is the function of the following parts of the nervous system:a) central nervous system Transmits and receives messages to and from Peripheral Nervous System (PNS)b) peripheral nervous system Carries messages to and from CNS c) brain Organises, intergrates and interprets neural information d) spinal cord Connects brain and PNSe) autonomic nervous system Carries messages from the CNS to the internal muscles, organs and glandsf) somatic nervous system Carries messages between CNS and the body.

6. Why are reflexes important to animals? Give an example of such a response. A reflex is a rapid action that helps to protect the animal from being attacked or eaten by prey.

7. What is the difference between voluntary and involuntary responses? Give an example of each. Involuntary response is an action that the body does automatically such as moving the hand away from a

hot object. Voluntary response is an action that the body is conscious of and can choose to make it such as running or jumping.

8. Name the three types of neurones.Motor neurone, sensory neurones, interconnecting neurones.

9. What are the differences between sensory neurones and motor neurones? Sensory neurons are the nerves that are used in our sense such as feeling if something is hot. Motor neurons are the nerves that control movement such as moving the arm away from the hot object.

10. Draw and label a neurone or nerve cell. Make sure you label the cell body, axon, myelin sheath, dendrites andthe direction the nervous impulse travels..

Direction of the nervous impulse

11. Draw a stimulus response model for:a. Touching a hot plate b. Stepping on a pin

12. What are the 4 lobes of the cerebral cortex? What are each of the lobes responsible for? Frontal Lobe – movement of skeletal muscles, Parietal Lobe – Reading, writing and mental arithmetic, Temporal Lobe – Important role in memory and occipital lobe – processing visual stimuli

13. What connects the 2 hemispheres? Corpus callosum – bundle of nerves in the centre of the brain.14. What are neurotransmitters? Name 2 and describe their function. Chemicals that helps communication across

nerve synapses – Dopamine – controls the brains reward and pleasure centres. Serotonin – sleep regulation.15. What is a psychoactive drug? A drug that alters the function of the brain and results in a change in a persons

behaviour16. When does physical dependence (on a drug) arise? When the brains neurons become adjusted to the presence

of the drug.17. Name 4 dangers of drug abuse. Addiction, overdosing, erratic behaviour, harm to self and others and death.18. When does drug tolerance occur? After prolonged use the body becomes adjusted to the drug therefore

requires more to get the desired effects.19. What is drug addiction? When a person is convinced they cannot function without the drug or their body needs

the drug to function.20. Outline the steps involved in a stimulus passing through a synapse (you may want to show your answer as a

diagram of a synapse)

21. Define the following terms in relation to psychological research:a. aim b. hypothesis A testable prediction of the relationship between two variables. Must contain direction, population, IV and DVc. independent variables condition an experimenter manipulates. d. dependent variables The condition in an experiment that is affected by the IV and is used as a measure of the IV’s effect. DV depends on IV.

e. experimental group the group of subjects that have been “treated”f. control group a group that has not been manipulated at all. Used as a comparison for results. g. Controls anything that needs to be kept the same in the experiment (eg. Temperature)

22. What are the correct steps in research methods?Step 1: Identify the research problem. Step 2: Formulate a hypothesis. Step 3: Design the method. Step 4: Collect the data. Step 5: Analyze the data. Step 6: Interpret the results. Step 7: Report the findings.

TOP I C 3: G LO B A L S Y S T EMS ( C H A P T ER 6)

1. What is the Earth’s largest and oldest store of carbon? Limestone (calcium carbonate)2. Identify the roles of

a. nitrifying bacteria Converts ammonia in the soil into nitrates.b. denitrifying bacteria Releases nitrogen compounds in the soil back into the atmospherec. nitrogen fixing bacteria Converts atmospheric nitrogen into ammonia.

3. Identify the two forms of nitrogen that plants are able to take up.Nitrates and nitrites

4. Compare the greenhouse effect and the enhanced greenhouse effect.Greenhouse effect occurs by natural agents releasing gases into the atmosphere. The enhanced greenhouse effect is caused by human activit y. Similarities: both emit greenhouse gases.

5. Label each number of the cycle below and explain each process

1 = Evaporation2 = precipitation3 = run-off4 = transpiration5 = condensation

6. What is the original source of energy for the water cycle?

7. List 3 ways carbon is released into the atmosphereRespiration, burning fossil fuels, decomposers, combustion, formation of fossil fuels.

8. Contrast between a carbon sink and a carbon sourceCarbon Sink = store

9. List 2 ways that atmospheric nitrogen is returned into the soil.Nitrogen fixing bacteria, through urine from animals, lightening, decomposition

10. Why is nitrogen important for both plants and animals?Makes up protein and DNA in organisms

11. Why is recycling of carbon important to the continued functioning of an ecosystem?12. Trees need this for photosynthesis. Without it, oxygen is not produced.13. Describe what animals appeared to have done when faced with rising temperatures in the past.14. Move to cooler areas. Some animals moved towards the poles during the warmer months and moved

towards the equator when it was cooler.15. Name the main greenhouse gases16. Methane, nitrous oxide, carbon dioxide, water vapour.17. Discuss the effects of global warming.18. Rising sea levels, increase in disease, melted ice caps, increase in average temperatures, ocean acidification 19. Refer to the image below of the carbon cycle.

a. Which arrow represents carbon dioxide being released by animals through respiration? 3b. Which arrow represents carbon dioxide taken in by plants? 1

20. Draw a diagram explaining the greenhouse effect

21. Explain the importance of the ozone layer Absorbs UV radiation emitted by the sun22. Identify sources of ozone depleting substances CFCs and Halogens found in refrigerators, air con, deodorant

and fire extinguishers23. Explain how ozone depleting substance destroy ozone UV radiation from the sun breaks the chlorine atom

from the CFC molecule which then reacts with oxygen found in ozone. This process is repeated.

TOP I C 4: GE O LO G I C A L T I ME + N A T UR A L S E L ECTION AN D E V OL UTI O N ( C H A PT E R S 2 AN D 3 )

1.2. What was the most dominant life form 250 – 65 million years ago? Reptiles3. How are indirect fossils formed? A mould becomes filled with sediment that turns to rock4. Discuss the difference between absolute and relative dating. List the types for each.Relative dating compares the age of one fossil with another to determine which is older. It does not provide an actual time/date. Examples of relative dating: Index fossils, layer by layer, fluorine analysis.Absolute provides an actual age of rocks and fossil. Examples of absolute: Radioactive dating (potassium – argon dating), tree rings. Similarities: both are techniques used to date fossils.

5. Define the following terms:a. homologous: Structures controlled by some of the same inherited genesb. analogous Structures that appear similar but controlled by different genes (eg. shark and dolphin)c. evolution change in the characteristics of a species over many generationsd. natural selection the process where an environmental factor acts on a population and results in some

organisms having more offspring than otherse. variation differences in characteristics due to different genesf. resistance inherited ability to withstand chemicals such as pesticidesg. artificial selection process where people choose to breed organisms for desirable features h. speciation process by which one species splits into two or more separate speciesi. divergent evolution Formation of new speciesj. convergent evolution Where two organisms have similar structures but not related. Just lives in

similar or same areas (eg. dolphin and shark)6. What does genetic isolation refer to? Keeping potentially interbreeding groups apart by some barrier.

7. Discuss the following types of environments where soft tissues are likely to be preserved in fossils:a. amber: organisms become trapped by sticky plant sap that solidifies and excludes oxygen and

moistureb. permafrost: permanently frozen that prevents bacteria from growing and therefore stop decay.c. peat: decaying moss that is very acidic and low in oxygen.

d. dry air: Desert winds dehydrate animals quickly preventing bacteria from growing.

8. Identify three characteristics that determine if a fossil is a suitable index fossil Must be widespread; lived in a fairly narrow time; have been abundant; easy to identify

9. Consider the three strata shown below. They occur in three different sites: A, B and C. Each layer has been numbered.

a. Identify the oldest strata over the three sites. (Give site and layer number.) B3

b. Identify the youngest strata in the three sites. A1/C1c. Identify a layer from site A that you would expect to be

found at site B, but which did not occur there. A4d. Identify the type of dating used. Stratification

10. Propose a suitable dating method for each of the following:a. Proving that two human skulls were not from the same location Fluorine dating b. dating a dinosaur bone found in a volcanic ash layerPotassium datingc. dating primitive looking stone tool found in a rock layer near an extinct volcanoRadioactive

11. Discuss differences and similarities between natural selection and artificial selection. Similarities: both act onindividuals and affect their chances of producing offspring. Differences: Natural selection - environment acts on a population. Artificial selection – humans choose and decide to produce offspring with favourable characteristics.

12. Describe the 4 different types of fossils and how they are formed. Original. Replacement. Carbon Film. Indirect13. List the evidence that supports evolution. Comparative anatomy, DNA structure, embryology, fossils

14. What does Lamarck’s theory suggest? If any part of the body is repeatedly used, it will remain on the body ormay increase in size.

15. Describe two ways in which a population may become geographically isolated to form two populations. Continental drift, earthquakes, rivers, lakes.

16. Suggest two reasons why the two separated populations may evolve differently. Different environmental conditions17. How could you determine if two organisms were of the same species? Bring them together, if they breed and produce fertile offspring they are the SAME species18. Complete the following table comparing both Homo sapiens and ancestral forms of humans. You must discuss the importance.

Homo Sapiens Primitive form of humans.Skull size Bigger – increased intelligence Smaller -

Walking Biped – multitask Quadraped (4 feet)

Feet Flat – walk on 2 feet Opposable toes for gripping

Teeth Reduced canines – different diet, can cook meat

Large canines for tearing raw meat

19. Discuss the impact of Gondwanaland separating in terms of populations evolving into different species.

One large land mass, when tectonic plates moves – caused continental drift. Organisms became ISOLATED on different pieces of lands, these moved towards different environments. Speciation occurred

20. Explain why humans, cats and whales all have homologous structures yet are from different species.

Suggests we originated from a common ancestor