3.4.5 Species and taxonomy ( 3.4 Genetic information , variation and relatoonships between organisms)

Question 1

what is a species

Answer 1

A group of organisms that can produce fertile offspring

Question 2

suggest why 2 different species are unable to produce fertile offspring

Answer 2

• different species have different chromosome numbers - offspring may have odd chromosome number
• so homologous pairs cannot form and meiosis cannot occur to produce gametes

Question 3

explain why courtship behaviour is a necessary precursor to successful mating

Answer 3

• allows recognition of members of same species - so fertile offspring produced
• allows recognition of opposite sex
• stimulates production of gametes
• indicates sexual maturity
• established a pair bond to raise young

Question 4

describe a phylogenetic classification system

Answer 4

• species arranged into groups called taxa based on their evolutionary origins and relationships
• uses a hierarchy :
- smaller groups are placed within larger groups
- no overlap between groups

Question 5

Name the taxa in the hierarchy of classification

Answer 5

1) domain
2) kingdom
3) phylum
4) class
5) order
6) family
7) genus
8) species

Question 6

suggest an advantage of binomial naming

Answer 6

universal so no confusion as many organisms have more than one common name

Question 7

how can phylogenetic trees be interpreted

Answer 7

• branch point = common ancestor
• branch = evolutionary path
• if two species have a more recent common ancestor, they are more closely related

Question 8

Describe two advantages that have helped to clarify evolutionary relationships between organisms

Answer 8

1) advances in genome sequencing - allowing comparison of DNA base sequences
• more differences in DNA base sequences - more distantly related / earlier common ancestor
• as mutations build up over time
2) Advanced in immunology - allowing comparison of protein tertiary structure
• higher amount of protein from one species binds to an antibody against the same protein from another species - more closely related
• as indicates a similar amino acid sequence and tertiary structure
• so less time for mutations to build up