3.4.5 - SPECIES AND TAXONOMY

Question 1

in taxonomy, an organism is identified by referring to the species name and genus name.

what term is used to describe this method of naming organisms? (1)

Answer 1

binomial system

Question 2

there are many different species of field mouse in europe. using a phylogenetic classification, all of these species have names that start with Apodemus

what information does this give about field mice? (2)

Answer 2

1. same genus
2. same evolutionary origin/common ancestor

Question 3

describe how breeding experiments could determine whether two populations are from the same species (2)

Answer 3

1. breed the two species together
2. if they are the same species they will produce fertile offspring

Question 4

some populations of animals that have never been hunted show very low levels of genetic diversity.

other than hunting, suggest two reasons why populations might show very low levels of genetic diversity (2)

Answer 4

1. inbreeding
2. population may have been very small - genetic bottleneck
3. population may have started with a small number of individuals - founder effect

Question 5

give three ways in which courtship behaviour increases the probability of successful mating (3)

Answer 5

any three:

1. recognise/identify/attract same species
2. stimulates/synchronises mating/production/release of gametes
3. recognition of opposite sex
4. indication of sexual maturity
5. formation of a pair bond

Question 6

what is meant by a hierarchy? (2)

Answer 6

1. small groups within larger groups
2. no overlap between these groups

Question 7

what is the effect of hunting on genetic diversity? (2)

Answer 7

1. hunting reduces population size (genetic bottleneck), so only a few alleles left (small gene pool)
2. inbreeding
3. population will be different to original, founder effect

Question 8

what is meant by genetic diversity? (1)

Answer 8

number of different alleles of each gene

Question 9

a zedonk is the offspring produced from breeding a mountain zebra with a donkey.

• the body cells of a mountain zebra contain 32 chromosomes
• the body cells of a donkey contain 62 chromosomes

use this information to suggest why zedonks are usually infertile (2)

Answer 9

1. zedonk has 47 (odd)number of chromosomes
2. so chromosomes cannot pair/are not homologous/chromosome number cannot be halved/meiosis cannot occur/sex cells not produced

Question 10

what is a species? (2)

Answer 10

1. group of similar organisms/organisms with similar features/same genes
2. that can produce fertile offspring

Question 11

explain what is meant by the term phylogenetic group (1)

Answer 11

grouped according to evolutionary links/history/relationships/common ancestry

Question 12

cytochrome c is more useful than haemoglobin for studying how closely related different organisms are. suggest one reason why (1)

Answer 12

1. all eukaryotic organisms have cytochrome c as they all respire
2. cytochrome c structure is more conserved/less varied between organisms

Question 13

state three comparisons of genetic diversity that a scientist would use in order to generate a classification (3)

Answer 13

1. the base sequence of DNA
2. the base sequence of mRNA
3. the amino acid sequence of proteins

Question 14

three of the bee species collected in the farmland areas were Peponapis pruinosa, Andrena chlorogaster and Andrena piperi

what do these names suggest about the evolutionary relationships between these bee species? explain your answer (2)

Answer 14

1. A. chlorogaster and A. piperi are more closely related to each other than P. pruinosa
2. because they are in the same genus

Question 15

haemoglobins are chemically similar molecules found in many different species.

differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.

explain how (5)

Answer 15

1. mutations change base sequence in DNA
2. causing change in amino acid sequence
3. mutations build up over time
4. there will be less differences in primary structure between closely related
5. closely related species have a recent common ancestor

Question 16

describe how organisms are grouped in a phylogenetic classification system (2)

Answer 16

1. hierarchy of smaller groups within larger groups with no overlap
2. grouped according to evolutionary history

Question 17

the classification system used in the early 20th century grouped different species of bacteria according to the position and shape of flagella on bacterial cells and by the number of flagella per cell. these were observed using an optical microscope. each species of bacterium has a characteristic cell shape and arrangement of flagella. these characteristics may be shared with other species within a genus. flagella are fragile, difficult to stain and may extend from the cell at any angle.

consider the accuracy and limitations of the early classification of bacteria using the arrangement of flagella (3)

Answer 17

1. can not identify/distinguish species
2. optical microscope resolution is too low
3. flagella are fragile so can be damaged OR artefacts may be misinterpreted for flagella
4. flagella difficult to stain, so not visible
5. flagella at an angle, so not visible
6. not all bacteria have flagella

Question 18

suggest why several bacteria species have been renamed in recent years (1)

Answer 18

ANY ONE:

1. DNA/mRNA/RNA base sequencing
2. amino acid sequencing
3. use of electron microscopes with greater resolution
4. use of electron microscopes and improved staining/preparation