life science grade 12 assignment 2023 term 3

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Life Sciences TG SSIP sessions 21-33 (Term 3) 2023 RK SW

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Life sciences:, teacher guide.

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TABLE OF CONTENTS

A session 21: responding to the environment:, b session 22: introduction to evolution 8, c session 23: lamarckism and darwinism 11, d session 24: punctuated equilibrium and, artificial selection, e session 25: speciation and reproductive, isolating mechanisms, f session 26: evolution in present times 25, g session 27: our place in the animal kingdom 29, h session 28: shared characteristics and, anatomical differences of apes and humans, i session 29: lines of evidence of human, j session 30: ‘out of africa’ hypothesis 39, k session 31: revision of paper 2 – nucleic, acids and meiosis.

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SESSION 2 1:

Responding to the environment: plants, concepts, plant hormones, uses in agriculture, phototropism &, geotropism, plant defence mechanisms, exam guideline (13 marks), plant hormones, − general functions of the following:.

• Gibberellins
• Abscisic acid

− The control of weeds using plant hormones

− the role of auxins in:.

• Phototropism

Plant defence mechanisms

− role of the following as plant defence mechanisms:, exam tips and techniques.

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• Examiners like to use this topic to ask scientific investigative questions.

Learners should know what a hypothesis is, variables: independent and

Dependent, how to control other variables, how to write a conclusion as well, as how to ensure validity and reliability.

• Look at the practice question. Learners did not do well in these questions.

NOTE : in a graph if the question is:

Draw a bar graph based on the results in the table.., the caption of the graph will be based on the variables on the table and not on the variables, stated in the aim of the investigation., caption: average increase in plumule length at different auxin concentration..

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Remember to include units in the Axis labels on the graph

Answers typical exam questions, (4 x 2) (8), 2 weedkiller/herbicide✓, 2 positive phototropism✓, 2 geotropism✓, 2 abscisic acid✓ ( 6 ), 3 both a and b✓✓, 4 the stimulate cell elongation✓/cell divison (1), 4 − to prevent weeds from competing with crops✓, − for water✓/nutirents/space/sunlight (2), 4 − they may kill other organisms✓, − they may accumulate in ecosystems✓, − they may disrupt ecosystems ✓, mark first one only, 4 − the application of auxin-based herbicide is less labour, intensive✓✓/less time-consuming/less expensive than, mechanical removal.

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− Shorter trees ✓ /development of lateral branches

− - makes harvesting of fruit easier ✓ any, 7 − auxins ✓ in the block of agar jelly, − move downwards ✓ into the stem, − causing (cell) elongation ✓ /growth, − resulting in upward growth of the stem (3), homework questions, question 8 (gde, sept. 2019, paper 1), 8 − it is the control ✓, − to verify the results of the experiment ✓ / to allow for, one variable only. (2), 8 as a result of receiving light from one side only:, − auxins produced in the tip of the stem ✓, − are unequally distributed ✓, − auxins moved to the shaded side of the stem✓, − where the concentration increased ✓, − thus promoting growth ✓, − whilst the brightly lit side with the lower concentration✓, − inhibited growth ✓, − resulting in the stem bending and growing towards the, 8 − use same type / species of plant ✓ / seeds, − use same type and amount of soil in the trays ✓, − watering at the same time of day ✓, − same amount of water given when watering shoots ✓, − same environmental conditions ✓ / temperature /, − same nutrients ✓, mark first two only.

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QUESTION 9 (DBE, May-June 2022, P1)

− auxins move away from light ✓, − there is a higher concentration of auxins on the dark, side of the stem ✓, − growth is stimulated ✓ on the dark side which, − grows faster ✓, − causing the stem to grow/bend towards the light ✓ (5), session 2 2 :, evolution through natural selection, concepts, introduction, evidence for evolution, variation, exam guideline (54 marks), introduction, − definition of biological evolution- change in the characteristics of species over, − difference between a hypothesis and a theory, − the theory of evolution is regarded as a scientific theory since various, hypotheses relating to evolution have been tested and verified over time, evidence for evolution, − role of the following as evidence for evolution:.

• Fossil record – Link to Grade 10
• Biogeography – Link to Grade 10
• Modification by descent (homologous structures)

− Definition of a biological species and a population

− a review of the contribution of each of the following to variation that exists, amongst individuals of the same species:.

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2 Mitochondrion✓

2 homologous✓structures, 2 crosssing over✓, 2 fossil✓record, 2 biological evolution✓, 2 biogeography✓, 2 extinction✓ ( 7 ), ( 3 x 2) ( 6 ), 4 genetic✓ evidence (1), 2 - c✓ or a, 3 - b✓ b ( 3 ), question 5 (kzn, sept 2022, p2), 5. (a) biogeography✓, (b) ability to fly✓, 6 modification by descent ✓ ( 1 ), 6 (a) p✓ and r✓, (b) p✓ and s✓.

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SESSION 23:

Lamarckism and darwinism, origin of an idea about origins, (a historical development), − ideas on evolution in the order of their origin are as follows:.

• Punctuated Equilibrium

(Jean Baptiste de Lamarck – 1744 – 1829)

− lamarck used two 'laws' to explain evolution:.

• 'Law' of use and disuse
• 'Law' of the inheritance of acquired characteristics

− Reasons for Lamarck's theory being rejected

(charles darwin – 1809 – 1882), − darwin's theory of evolution by natural selection:.

• There is a great deal of variation amongst the offspring.
• Some have favourable characteristics, and some do not.
• When there is a change in the environmental conditions or if there is

competition,

• then organisms with characteristics, which make them more suited,
• whilst organisms with unfavourable characteristics, which make them less

suited, die.

• The organisms that survive, reproduce
• and thus, pass on the allele for the favourable characteristic to their
• The next generation will therefore have a higher proportion of individuals

with the favourable characteristic.

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TYPICAL EXAM QUESTIONS

( 4 x 2) ( 8 ), 2 variation✓, 2 (biologica)l evolution✓, 2 natural selection✓, 2 law of use and disuse✓ ( 5 ), 3 ambulocetus ✓ (1), 3 it had flipper-like large feet and a tail ✓✓ (2), 3 − they share characteristics ✓ /have intermediate characteristics, − of the ancestor/pakicetus and the present-day species ✓ / balaena, − they have legs like pakicetus✓ and, − flippers of the present day balaena✓, 3 − ancestral species of whales all had legs✓/lived on land, − as more time was spent in the water✓in search of food, − the legs were used less✓ and disappeared, − the acquired characteristic was passed on to the next generation✓ (3), question 4 (fs, sept 2022, p2), 4 − predators may mistake it ✓/avoid eating them, − because they resemble a. ochlea which has an unpleasant taste✓ ( 2 ), 4 − there was a variation in the appearance and taste of butterflies✓, − the amauris ochlea did have an unpleasant taste and the, hypolimnas deceptor that looks like the amauris ochlea did not, have an unpleasant taste✓, − predators feed on butterflies in this habitat✓.

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− Hypolimnas deceptor that look like the Amauris ochlea with the

Unpleasant taste were avoided by predators✓/ predators did not, prey on them, − they were mistaken by their appearance for unpleasant taste✓, − the hypolimnas deceptor survive✓, − they reproduced and✓, − passed the allele of appearance/allele of looking similar to amauris, ochlea to the offspring✓, − more hypolimnas deceptor butterflies is in the next generation that, look like amauris ochlea.✓.

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− the resistant viruses survive and reproduce✓

− passing the resistance to their offspring✓ (5), question 7 (dbe, may-june 2021, p2), 7 (a) lamarck, − he would use his law of use and disuse✓, − and the law of inheritance of aquired characteristics✓, − the ancestor of spider monkeys had short tails✓, − the ancestors continually stretched✓/used their tails, − to be able to hold on to tree branches✓, − as a result, their tails became longer✓, − and this characteristic was passed on to the next, generation✓, − evolution occurs by the natural selection✓, − there was variation in the ancestral population✓, − some spider monkeys had short tails✓, − and some had long tails✓, − those with short tails could not hold onto tree branches✓/, fell on the ground, − they died✓/were attacked by predators, − the spider monkeys with long tails were able to hold onto, tree branches✓/did not fall to the ground, − and survived✓/were not attacked by predators, − and reproduced✓, − the characteristic for long tails was passed to the offspring✓.

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SESSION 24:

Punctuated equilibrium and artificial selection, punctuated equilibrium (eldredge and gould – 1972), − punctuated equilibrium explains the speed at which evolution takes.

• Evolution involves long periods of time where species do not change or

change gradually through natural selection (known as equilibrium).

• This alternates with (is punctuated by) short periods of time where rapid

changes occur through natural selection during which new species may

Form in a short period of time., − artificial selection involving:.

• A domesticated animal species
• A crop species

ICT Resources

Gr 12 LS - Punctuated equilibrium artificial selection

Punctuated Equilibrium (Eldredge and Gould: 1972)

Punctuated equilibrium explains the speed at which evolution takes place:, artificial selection is the intentional reproduction of individuals in a population that, have desirable traits..

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4 − Rhodesian ridgeback✓

− is strong, athletic and fast✓, − to enable it to catch the prey✓, 4 − they will not be able to hunt✓/find shelter/defend themselves, − as well as wolves are able to✓, − therefore unable to survive in the wild✓ (3), question 5 (gde exemplar, nov. 2021 paper 2), 5 the purposeful selection of certain characteristics to make the species, more useful to humans/to satisfy human needs (2), 5 marino sheep /a (1), 5 − to increase the productivity and profit, − animals are selected for their characteristics to produce large, amounts of wool /milk/ meat, 5 − in artificial selection, humans select a desired characteristic, − in natural selection nature selects the characteristic, − in artificial selection, humans select organisms to breed whereas, − in natural selection breeding is random, − in artificial selection, more than one species may be involved, whereas in natural selection only one species is involved, − in artificial selection, the characteristics of the population do not, necessarily changewhereas, − in natural selection, the characteristics of the population change, mark first one only (any 1 x 2), 5 (a) advantage:, − it allows for higher profit /new varieties/ higher quality of, products/ fitter or stronger animals, (b) disadvantages:, − it can lead to loss of species variety, − it cannot control genetic mutations , − inbreeding of a species can lead to diseases and disorders, becoming prevalent, mark first two only (any 2).

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QUESTION 5 (GDE, Sept 2021, P2)

Natural selection artificial selection, nature selects the desired, characteristic✓ /the environment or, nature is the selective force, humans select a desired characteristic✓ /, humans represent the selective force, the characteristic improves chances, of survival✓, human needs are fulfilled✓, mating is random✓ humans select organisms to breed✓, the characteristics of the population, the characteristics of the population do not, necessarily change✓, occurs within a species✓ may involve more than one species✓, mark first three only any (3 x 2) + 1 table (7), 5 − evolution involves long periods of time where species do not change/or, change gradually through natural selection as shown by a✓✓, − these alternate with/are punctuated by short periods of time where rapid, changes occur through natural selection as shown by b. ✓✓ (4).

• Multiple Choice

Subject : Life Sciences

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