3.4.5 - species and taxonomy

Question 1

what are species?

Answer 1

organisms with similar features which can interbreed to produce fertile offspring

Question 2

what does a phylogenetic classification system do?

Answer 2

arrange species into groups based on their evolutionary origins and relationships

Question 3

how do phylogenetic classification systems work?

Answer 3

they use a hierarchy where smaller groups are placed within larger groups with no overlap between groups

Question 4

what is the name of a group in a phylogenetic classification system?

Answer 4

a taxon (plural taxa)

Question 5

what are the taxa within one hierarchy of a phylogenetic classification system?

Answer 5

domain, kingdom, phylum, class, order, family, genus, species

Question 6

how are species universally identified?

Answer 6

by a binomial which contains their genus and species eg. Homo sapiens

Question 7

what is speciation?

Answer 7

a process through which new species arise from an existing species

Question 8

how is natural selection involved in the process of speciation?

Answer 8

1. variation exists within a gene pool when DNA mutations result in new alleles
2. the best adapted survive and reproduce
3. the best alleles are passed on
4. the allele frequency increases

Question 9

which processes can lead to variation?

Answer 9

mutations
change in environment
meiosis
random fertilisation

Question 10

what is allopatric speciation?

Answer 10

speciation occurring due to geographic isolation of species

Question 11

how does allopatric speciation occur?

Answer 11

1. a population is separated from another population of the same species by a physical barrier preventing reproduction and hence gene flow between the population
2. the two populations experience different selection pressures
3. gradually, their allele frequency and type changes due to natural selection, so the population has evolved (adaptive radiation)
4. eventually they would not longer be able to interbreed if reintroduced, so they are different species

Question 12

what is sympatric speciation?

Answer 12

speciation occurring within a population in the same area, resulting in reproductive isolation

Question 13

why might sympatric speciation occur?

Answer 13

different breeding seasons (temporal)
courtship behaviour
anatomical differences (mechanical)
gametic

Question 14

how does genetic drift occur?

Answer 14

1. it takes place in small populations due to a smaller variety of alleles
2. the reduced genetic diversity means any advantageous mutations quickly affect the whole population
3. the population change more rapidly so they are more likely to develop into separate species
4. in large populations, the mutant allele will be diluted so development into a new species is slower

Question 15

what is courtship behaviour?

Answer 15

a necessary precursor to successful mating

Question 16

what are key features of courtship behaviour?

Answer 16

• it is species specific (only members of same species perform and respond to that behaviour)
• the more closely related species are. the more similar their courtship behaviour

Question 17

why is it important that courtship behaviour is species specific?

Answer 17

it allows for species recognition and prevents interbreeding to make reproduction successful

Question 18

what does courtship behaviour enable individuals to do?

Answer 18

• recognise members of their own species (as only members of same species can produce fertile offspring)
• identify a mate capable of breeding
• form a pair bond (leads to successful mating and raising of offspring)
• synchronise mating (occurs when max probability of sperm and egg meeting)
• become able to breed (brings member of opposite sex into physiological state for breeding to occur)

Question 19

how can genome sequencing clarify evolutionary relationships between organisms?

Answer 19

• it allows the entire base sequence of an organism’s DNA to be determined
• base sequencs of different organisms can be compared to see how closely related they are
• species with a higher percentage of base sequence similarity will be more closely related

Question 20

how can amino acid sequences clarify evolutionary relationships between organisms?

Answer 20

• the amino acid sequence is coded for by the base sequence
• organisms with similar DNA base sequences will have similar amino acid sequences in their proteins
• mRNA sequences can also be compared

Question 21

how can immunology clarify evolutionary relationships between organisms?

Answer 21

similar proteins will bind to the same antibody

Question 22

what does closely related mean?

Answer 22

two species have evolved from a common ancestor in the recent past