4.5 Species And Taxonomy

Question 1

What is a species?

Answer 1

A group of organisms that can interbreed to 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 -> 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 / attraction of opposite sex
• stimulates / synchronises mating / production / release of gametes
• indicates sexual maturity / fertility
• establishes a pair bond to raise young

Question 4

Describe a phylogenetic classification system

Answer 4

• species attempted to be arranged into groups called taxa, based on their evolutionary origins and relationships
• uses a hierarchy:
  
  • smaller groups are places 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

How is each species universally identified?

Answer 6

A binomial consisting of the name of its genus and species e.g. homo sapiens

Question 7

Suggest an advantage of binomial naming

Answer 7

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

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 mutation (changes in DNA base sequences) build up over time
2. Advances in immunology -> allowing comparison of protein tertiary structure (e.g. albumin)
   - higher amount of protein from one species binds to antibody against the same protein from another species -> more closely related / more recent common ancestor
   - as indicates a similar amino acid sequence and tertiary structure
   - so less time for mutations to build