Species and Classification

Question 1

define species

Answer 1

a group of organisms that are similar to each other and are capable of reproducing sexually to produce fertile offspring

Question 2

what are some difficulties with defining species?

Answer 2

• species are not fixed
• considerable variation within a species
• lots of species extinct without fossil records or fossil records are incomplete
• some species rarely, if ever reproduce sexually
• some populations of organisms are isolated from each other may be classified as separate species but may be the same species

Question 3

describe the courtship process

Answer 3

• the male may perform a specific sign stimulus
• this will elicit a response from the female that encourages a further action from the male
• the process repeats in the stimulus response chain
• if at any point appropriate responses are not performed then the courtship ritual stops

Question 4

what do courtship behaviours allow individuals to do?

Answer 4

• recognise members of the same species to ensure that mating occurs only between members of the same species
• identify a mate that is capable of breeding both partners are sexually mature, fertile and receptive to mating
• form a pair bond leading to successful mating and raising of offspring
• synchronise mating ensuring that mating occurs when there is the maximum probability of the sperm and egg meeting

Question 5

what are the two types of classification?

Answer 5

• artificial classification, divides organisms by physical characteristics, such as size or number of legs, describes by the same function, not the same evolutionary origin
• phylogenetic classification based upon the evolutionary relationships, classifies species using shared features derived from their ancestors, arranges the groups into a hierarchy, groups contained within larger groups with no overlap

Question 6

what is taxonomy?

Answer 6

the most respected classification system (phylogenetic) it takes into account evolutionary origins of organisms. it is the universally accepted scientific method for classification of organisms

Question 7

what is a hierarchical system?

Answer 7

large groups split into smaller groups, which do not overlap

Question 8

whats the names of the taxa in order?

Answer 8

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 9

whats the mnemonic to remember the order of the taxa?

Answer 9

Dear
King
Philip
Came
Over
For
Great
Soup

Question 10

what are the three domains?

Answer 10

bacteria, archaea, eukarya

Question 11

what is the binomal system?

Answer 11

the naming system for each species, there are two parts to the name
- the genus to which the organism belongs
- the species to which the organism belongs

Question 12

what are the rules for naming through the binomal system?

Answer 12

• the names are printed in italics or underlined if handwritten
• the first letter of the generic name is capitalised and the specific name is not

Question 13

how can you determine the evolutionary relationship between two species by comparing the DNA base sequences?

Answer 13

closely related species will have a high% similarity
distantly related species will have a low% similarity
this is because members of the same species will have very similar DNA base sequences.

Question 14

how can you determine the evolutionary relationship between two species by comparing the base sequence of mRNA?

Answer 14

you can find the similarity of the DNA base sequence in one gene, rather than a genome. it can indicate how closely related a species is.
it doesn’t tell you about introns because mRNA has none

Question 15

can you determine the evolutionary relationship between two species by comparing the amino acid sequences in proteins?

Answer 15

it can only give information about how similar the DNA is. however it doesn’t tell you about introns and the genetic code is degenerate so the amino acids don’t guarantee the genetic base sequence

Question 16

before genetic sequencing was available how did we compare genetic diversity?

Answer 16

by comparing observable characteristics, individuals of closely related species will look similar and have similar physical characteristics and physical appearance.
however
1) most observable characteristics are coded for by more than one gene
2) characteristics can be modified by the environment