AQA AS Biology B10 Biodiversity Kerboodle Answers

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10.1 Species and taxonomy AQA AS Biology B10  Biodiversity Kerboodle Answers

Ans 1 Members of a species are capable of breeding and produce living and fertile offspring. This will result in more offspring production. When a species reproduces sexually then any of the genes of its individuals can, in theory, be combined with any other. Besides this they share a common ancestor.

Ans 2 Three features of phylogenetic system of classification are as follow:

• it is based upon the evolutionary relationship between organisms and their ancestors.
• Species are classified into groups using shared features which are derived from their ancestors. Groups are arranged into a hierarchy.
• In hierarchy groups are contained within larger composite groups with no overlap.

Ans3 Courtship enables individuals to recognise members of the same species to ensure that mating only takes place between members of the same species because only members of the same species will produce fertile offspring.

Ans 4. Courtship behaviour of one species is used to determine which of two other species is most closely related to it because courtship behaviour is species specific. Two closely related species will show more similar courtship behaviour.

Ans 5

Kingdom	Animalia
(1) Phylum	Chordata
(2) Class	Amphibia
(3) Order	Anura
(4) Family	Ranidae
Genus	(5) Rana
(6) Species	(7) tempporaria

Ans 6 a Lizards are closest relatives of the snakes.

b.Ans Dinosaurs are more closely related to birds.

1. Ans In this phylogenetic tree C represents most recent common ancestor for lizards and snakes.

d.

Ans Dinosaurs are not shown along the time line like all the other groups because they became extinct. They are not present on the Earth today.

The difficulties of defining species

 

Ans 1.1.  Fossil remains are often only the hard tissues and even then each specimen is often damaged in certain places so it is difficult to obtain enough specimens that are well preserved to compare them really well at this level. Even though soft tissues are sometimes discovered it may only be in one or two individuals. It is not possible to get an accurate understanding of natural diversity within a species from fossils. For example if you were looking at fossilized honeybees some time in the future, the queen is much larger than the workers – would you be able to guess that they were all the same species just from exoskeleton remains? It is much more likely that you would assign them to different species. The ultimate molecule for helping you work all of this out – DNA – is not present in fossils.

2. The DNA in fossils is extremely old and therefore highly likely to be damaged. If we cannot figure out the gene sequences and hence, variations which might occur within a species then we cannot easily distinguish between species that create superficially similar casts or have almost identical bone structure.

Ans It is difficult to classify organisms as distinct species because:

• Species changes and evolve with time. With time some individuals of a species may develop into a new species.
• There is considerable variation among individuals of same species. For example all dogs are grouped into same species but because of the variation artificial selection took place which led to a variety of different breeds.
• There are species which became extinct and have not left any fossil record.
• There are some species which rarely reproduces sexually such as lizards, sharks, and bacteria.
• There are geographical barriers, such as oceans which result in no sexual reproduction between same species.
• Some types of organisms are sterile.

A horse and donkey are capable of mating and producing offspring known as mules. Mules are infertile. Horse and donkey are two different species. Mules are sterile due to the number of chromosomes present in them which will result in abnormal first stage of meiosis. Horse has 64 chromosomes (32 pairs) and donkey has 62 chromosomes (31 pairs). When the gamete of horse fuse with gamete of donkey the resultant zygote has 32 horse chromosomes and 31 donkey chromosomes thus in total 63 chromosomes. Thus during meiosis due to the odd number of chromosome pairing will not occur, so the non functional gametes form. This is the reason why mules are sterile.

Figure: Horse, donkey and mule. Source: http://ib.bioninja.com.au/standard-level/topic-3-genetics/32-chromosomes/chromosome-number.html

Very rare chance is there that a mule can be fertile and that is once in a blue moon.

3.Ans In mules, only females are ever fertile. In males there is no spermatogenesis because of the failure of meiosis. Also, in the overwhelming majority of cases, fertile females produce viable eggs by discarding their donkey father’s chromosomes, doubling their horse mother’s chromosomes and starting meiosis from scratch. If then crossed with a horse, the offspring is a horse. So a mule is not a species as it doesn’t create offspring of its own kind and one sex is always sterile so is not part of the gene pool. In a few very rare cases, chimaera mule offspring have been found with a few donkey genes but these are just the exceptions that prove the general rule.

10.2 Diversity within a community AQA AS Biology B10  Biodiversity Kerboodle Answers

Ans1-Species is a basic unit of classification and is defined as a group of similar organisms that mate and produce offspring’s with one another and thus, share a common lineage. The numbers of species of plants and animals that are present in a region constitutes its species diversity.

Ans2 Total number of species are = 6,

Total number of individuals are (N) = 58.

Species	Numbers in salt marsh	n(n-1)
Salicornia maritime	24	24(23) = 552
Halimione portulacoides	20	20(19) = 380
Festuca rubra	7	7(6) = 42
Aster tripolium	3	3(2) = 6
Limonium humile	3	3(2) = 6
Suaeda maritima	1	1(0) = 0
	58	986

Thus for species diversity:

N= 58;  = 986.

d= 58(57)/986 = 3306/986 = 3.35.

Ans 3 A species diversity index gives a broader interpretation of the differences between two habitats because it takes the smaller and larger numbers into account.

Species diversity and ecosystems:

Ans Adverse environmental conditions such as changing climate will more affect communities with less species diversity than the communities with high species diversity. In a community with high species diversity it is much more likely that a species tolerate the changing condition and survive but not in case of community with low species diversity. Survived one member will maintain the community.

1. Ans There is a direct impact of changing environment can be seen on the communities with low species diversity. As the degree of change in environment increase the degree of change in community with low species diversity also increase. That means these types of communities are dominated by the climate rather than by the organisms living in it.

b.Ans Communities with low and high species diversity respond to environmental conditions differently because of the following reason:

Communities with low species diversity are dominated by the environment rather than by the organisms living in it. In this type of community only few of the organism will get adapt to the changed environmental conditions.

Communities with high species diversity are dominated by the organisms living in ti rather than by the environmental conditions. In a community with high species diversity it is much more likely that a species tolerate the changing condition and survive but not in case of community with low species diversity. Survived one member will maintain the community.

10.3 Species diversity and human activities AQA AS Biology B10  Biodiversity Kerboodle Answers

1.Ans In case of agriculture most of the area is taken up by the one species that the farmer consider desirable. Thus there is smaller area available for all the other species. These species need to compete for the resources and space available. Only few species will conquest the competition thus their population of the species would be considerable reduced. Because agriculture is focused towards only a single crop yield thus farmers use pesticides to get rid of these competitive species. Competition between different species with the major crop, use of pesticides and human intervention resulted in reduced species diversity and low species diversity in agriculture ecosystems.

2.Ans Forests are richer in species diversity index when compared to grassland. Cattle grazing will further result in decreases species diversity.

3.Ans Ponds provide a habitat for a large range of aquatic species that are unlikely to find alternative habitats because aquatic habitats are few and far between. Ponds may be a source of food and water for terrestrial species which may not survive without them.
Hedgerow species are likely to have a larger range of alternative habitats as most of the area around will be terrestrial with other sources of food and shelter thus fewer species will be lost.

Human activity and loss of species in the UK

1.Ans y= x-30% of x

Where y= current hedgerow is 350000 km

x= hedgerow in 1900

Hence 350000= x (1-30/100) = 350000 = 70x/ 100 = x= 350000*100/ 70 = 500000.

Thus the hedgerow in UK in 1900 was 500000 km.

2.Ans Low land mixed woodlands are rich in species diversity. If they are replaced by some other type of woodland it will result in lower species diversity because low land mixed woodland have a tendency to grow in any kind of soils thus when they are replaced by any other woodland there are chances that the new woodland species will not survive thus species diversity is lost in this change.

3.Ans Advantage of conserving hay meadows and chalk grasslands to highly productive grass and silage is that the species diversity remains high. Because in case of hay meadows and chalk grasslands, the species diversity index is higher than the maintained fields of productive grasses and silage.

One  risk associated with this in order to conserve hay meadows and chalk grassland one has to compromise with the crops and productivity in terms of yield and economy.

4.Ans By looking at the reasons why the habitats are becoming extinct one can make decision in order to prevent the habitats and biodiversity.

5.Ans Hedgerows increase the species diversity on farms because they provide shelter to many species which move to disperse themselves into hedgerows. Removal of hedgerows resulted in soil infertility and soil erosion also. Hedgerows act as natural boundaries in farms. Thus replanting hedgerows will create an impact on the species diversity of the farm and will restore the lost soil infertility.

Hedge rows!

1.Ans Intensive farming has increased dramatically in the last 50 years, due to technological developments. Three ways in which the removal of hedges might benefit the farmer by increasing crop yields are as following:

1. To get the biggest yield from their land, farmers must use heavy machinery such as combine harvesters.
2. The size of such machinery means that they can only be used efficiently in large fields, in order to minimise turning circles. = hedges removed to make big fields.
3. Removing hedgerows literally leaves more space for crops and saves time and money on hedge maintenance.

2.Ans Hedgerows increase the species diversity on farms because they provide shelter to livestocks which can move to disperse themselves into hedgerows. Removal of hedgerows resulted in soil infertility and soil erosion also. Hedgerows act as natural boundaries in farms. Thus replanting hedgerows will create an impact on the species diversity of the farm and will restore the lost soil infertility.

10.4 Investing diversity AQA AS Biology B10  Biodiversity Kerboodle Answers

1.Ans: DNA sequences of a gene changes over a period of time because of the mutations and environmental factors as well.

2.Ans Species 1 and 6, are more closely related species. Because these two species show more similarities and less number of differences at the level of amino acid sequence.

Establishing relationship: 

1Ans Starting from more closely related species and ending with most distantly related species: Chimpanzee; Gorilla; Orang-utan; Lemur; Gibbon.

2.Ans Chimpanzee and gorilla are closely related primates to human because the rate of precipitation in serum of both species is high with the human blood protein antibodies raised in rabbit. That means chimpanzee and gorilla shows similarities at the protein levels with human.

3.Ans Gibbon is the nearest relative of orang-utan because the percent precipitation is 85% in orang-utan and 82% in gibbon. Thus we can say that they are closer to each other rather than to human.

4.Ans. According to haemoglobin study human are closer to lemur than the gibbon but in case of immunological studies human are closer to gibbon than the lemur.

Scientist did study and compared the number of base differences in the first 200 bases of a gene found in five species of primates. Results of the study are shown in table 2.

All the study done to interpret the relationship between different primates illustrates the need to use a variety of evidence from different sources in drawing valid scientific conclusions.

5.Ans Table 2 shows the number of base differences in the first 200 bases of a gene found in five species of primates. That means less the differences more the primates are related to each other. When we compare human with Orang-utan and lemur, it is clear that human are more closely related to Orang-utan (number of differences are 29) than to lemurs (number of difference are 48).

6.Ans According to these data Gorilla is more closely related to human than the chimpanzees whereas the previous studies show that human are more closely related to chimpanzees rather than gorilla. Thus it is clear that all the studies show somewhere different relationships between all these five primates. This illustrates the need to use a variety of evidence from different sources in drawing valid scientific conclusions.

10.5 Quantitative investigations of variation AQA AS Biology B10  Biodiversity Kerboodle Answers

1.Ans In sampling measurements of individuals are taken. Individuals are selected from a population. According to the theories if these individuals are representative of the population as whole then the measurements can be relied upon. But it is not sure that the measurements are representative of the populations because:

• Sampling bias: selection of individuals may be biased. It may be possible that the investigator is making unrepresentative choices. This could be either deliberately or unwillingly. It may not be possible to collect buttercup plant sample from different locations.
• Chance: Even if sampling bias is avoided by investigator and the individuals chosen by pure chance but cannot represent the whole population. It could be possible that the 50 buttercup plants selected just happen to be the first tallest 50 plants of the population.

2.Ans By using sampling process we cannot completely remove chance from the sampling process but we can only minimise its effect by:

• Using a large sample size: The more the number of individuals selected the smaller the probability that chance will influence the result, and less influence anomalies will have. The greater the sample size the more reliable the data will be.
• Analysis o the data collected: by using statistical test the extent by which the chance may have influenced the data can be determine. These tests allow us to determine whether any variation observed is the result of chance or is more likely to have some other cause.

3.Ans The mean (arithmetic mean)

This is the sum of the sampled values divided by the number of items. In table 1, total number of children in all families and divided by the number of families:

Total children= 0+1+1+1+2+2+3+4+6+6+7 =33

Total number of families: A-K = 11

Mean = 33/ 11 =3.

The mode

 

This is the single value of a sample that occurs most often. In our example, more families have one child than any other number. The mode is therefore equal to 1.

The median

 

Median is the central value or middle value of a set of values. This requires arranging the values in ascending order. In our example, they are already arranged in ascending order of the number of children is each family. There are 11 families. The sixth family is therefore the middle family in the sample. This is family F and has two children. So the median is 2.

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Practice questions:

1.Ans (a) Basic unit of classification is a species. Species definition is not easy but members of a single species have one main thing in common: Members of a species are capable of breeding and produce living and fertile offspring. This will result in more offspring production. When a species reproduces sexually then any of the genes of its individuals can, in theory, be combined with any other.

Ans b (i) Total number of plant species = 8

Plant Species	Number of individuals	n(n-1)
Himalayan raspberry	20	20(19) = 380
Heartwing sorrel	15	15(14) = 210
Shala tree	09	9(8) = 72
Tussock	10	10(9) = 90
Read cedar	04	4(3) = 12
Asan Tree	06	6(5) = 30
Spanish needle	8	8(7) = 56
Feverfew	8	8(7)=56
	N=80	906

Thus for species diversity:

N= 80 ;  = 906.

d= 80(79)/986 = 6320/906 = 6.97.

Thus species diversity index of the forest is 6.97.

Ans b(ii) Clearing of forest will result in decreased variety of plants. Habitats will be lost. Because of this there will decrease in variety of food and food sources which will result in a sharp decrease in insects. Besides this to protect crops in the agriculture fields farms use pesticides that will further kill the insects.

2.Ans a(i) A group within a group; no overlap between the groups

Ans a (ii) Grouped according to evolutionary links/history/relationships/common ancestry

Ans b (i) Because the protein sequence of cytochrome c has only one difference in case of species A when compared to the cytochrome c sequence of human.

Ans b (ii) Here the table is showing the relation of all species with human. But not with the species B and C. Thus it is not valid point that species B and C are more closely related.

Ans b (iii) Because all organisms respire and therefore will have cytochrome c. Cytochrome c structure is is less varied between organisms. Thus cytochrome c is more useful than haemoglobin for studying how closely related different organisms are.

3Ans (a). Number of each species and 2. Total number of individuals of all species.

Ans (b) Clearing of forest will result in decreased variety of plants. Habitats will be lost. Because of this there will decrease in variety of food and food sources which will result in a sharp decrease in insects. Besides this to protect crops in the agriculture fields’ farms use pesticides that will further kill the insects.

Ans c (i) because in this case graph is used to read the intermediate values so it needs to be best fit. And straight lines are used to draw best fit curves.

Ans c(ii) To have a control ditch will be useful because we can see the change in pattern of number of breeding birds.

Ans Clearing the plants from one bank will not decrease the birds diversity. Clearing both the bank will decrease the bird diversity. Plants on one bank can provide shelter or habitat to the birds.

4.Ans  (a) More plants resulted in the high number of habitats and also they provide shelters to the different animals. The variety of food sources will also be available in high species diversity index.

Ans (b). Index of diversity is more useful measure of biodiversity because

1. it also measures number of individuals in a specie/different proportions of species;
   2. Some species may be present in low/high numbers;

Ans.c As it is stated that eggs are very small. Thus the rate of diffusion of pesticides into eggs is more and as frog can move out of water but eggs cannot. Thus frog eggs are very likely to be affected by pesticides in the water.

Ans ii) Evaporation of water resulted in increased concentration of pesticides in water thus evaporation may increase the effect of pesticides on frogs’ eggs.

.

5.Ans a) No, as the graph only shows the number of species that were resistant, not the names of the species

Ansb)No, as mutations are spontaneous and random Environmental factors only affect the rate at which mutations occur Species cannot interbreed as they do not produce fertile offspring
So the mutated allele for resistance to the toxin cannot be passed from one species to another

Ans c) 1. Initially, one one or a few individuals possessed the favoured mutated allele enabling resistance
2. This individual must then survive and reproduce to have more offspring
3. It takes time for the mutated allele to become the most common allele of a gene within a species.

Ans d) The actual area used to grow Bt crops is increased between 2000 and 2010. In 2000 it is 0 Bt crops/10⁶ ha but in case of 2010 it is 50 Bt crops/10⁶ ha.

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