A3.1 - diversity within organisms (5a)

Question 1

why is variation considered a defining feature of life?

Answer 1

no 2 individuals are identical in all their traits
- the patterns of variation are complex and are the basis for naming and classifying organisms

Question 2

what is the biological species concept?

Answer 2

a species is a group of organisms that can interbreed and produce fertile offspring

Question 3

what are the 5 limitations of the biological species concept?

Answer 3

• not all individuals in a species are fertile, so a false negative outcome may occur
• may not be possible to see if two individuals can interbreed due to their extinct nature, inability to survive in captivity or inability to accurately track organisms
• hybrids (resulting from parents of closely related species) are infertile
• definition doesn’t apply to organisms that reproduce asexually as they do not interbreed
• arbitrary decision whether 2 populations are regarded as same or different species at a given time during speciation

Question 4

how can speciation occur?

Answer 4

during speciation, the divergence of non-interbreeding populations usually happens gradually rather than by a single act, demonstrated by:
- populations becoming more and more different in their traits
- gradual decline in the success rate of interbreeding

Question 5

what are the difficulties in distinguishing between populations and species?

Answer 5

• members of a species may be reproductively isolated in separate populations
• as there is no interbreeding between populations, speciation may occur if there are different selection in each population, causing the separate populations to become separate species

Question 6

what is the morphological species concept?

Answer 6

a species are a group of organisms with shared traits
- this concept was used by Linnaeus

Question 7

what is the genetic definition for species?

Answer 7

individuals in a species have the same chromosome number and the same types of chromosomes, which have the same sequence of genes

Question 8

what is the ecological niche definition for species?

Answer 8

species are a group of organisms based on where they live, what they eat and the molecules they produce

Question 9

what is binomial nomenclature?

Answer 9

• every species is given a binomial name
• the first part of the name identifies the genus, with the second part of the name distinguishing the species
• species in the same genus have similar traits, caused by having similar DNA and common ancestry

Question 10

how are binomial names formatted?

Answer 10

1. the genus name is given an initial capital letter but the species name is a small letter
2. the whole binomial name is italicised, if typed, or underlined, if hand-written

Question 11

what is a genome?

Answer 11

all the genetic information of an organism

Question 12

why do species in the same genus have similar traits to each other?

Answer 12

similar DNA sequence (genome)

common ancestory

Question 13

why are individuals of the same species more similar than those of another species?

Answer 13

within a species, all individuals (except those with genetic conditions) have the same number of chromosomes and genes, in the same locations on the same chromosomes

Question 14

what is the type of variation that gives diversity in the genomes within a species?

Answer 14

variations such as single-nucleotide polymorphisms (SNP’s) give some diversity