Genetic Information and Variation - Species and Taxonomy

Question 1

What is classification?

Answer 1

Classification is the organisation of living organisms into groups. This process is not random but is based on a number of accepted principles.

Question 2

What is a species?

Answer 2

A species is the basic unit of classification.

They are capable of breeding to produce living (viable), FERTILE offspring. They are therefore able to produce more offspring. This means that, when a species reproduces sexually, any of the genes of its individuals can, in theory, be combined with any other.

Question 3

What is a niche?

Answer 3

Individuals belong to the same species if they occupy the same niche. A niche is an organism’s ecological role.

Question 4

What is the competitive exclusion principle?

Answer 4

States that two species with identical niches cannot coexist without one of them being competitively excluded.

Question 5

How do niches affect species diversity?

Answer 5

The more niches a habitat has, the higher its species diversity.

Question 6

What is the binomial system?

Answer 6

• the first name (generic name) denotes the genus to which the organism belongs
• the second name (specific name) denotes the species to which the organism belongs to

When hand writing these, the names must be underlined and the first letter of the generic name must be capitalised, but not the first letter of the specific name.

Question 7

What is courtship behaviour?

Answer 7

The behaviour, like physical characteristics, of members of the same species is more alike than that of members of different species.

The ability to display a behaviour is genetically determined. It too has evolved and it influences the chances of survival.

Question 8

Why is it important to ensure that mating is successful?

Answer 8

Reproduction is the means by which a species can survive over time. Each individual has adaptations that help to ensure that their DNA is passed on to the next generation.

The females of most species only produce eggs at specific times, often as little as once a year. It is therefore important to ensure that mating is successful and that the offspring have the maximum chance of survival.

Question 9

How does courtship behaviour help to achieve successful mating?

Answer 9

By enabling individuals to:

• recognise members of their own species to ensure that mating only takes place between members of the same species because only members of the same species can produce fertile offspring
• identify a mate that is capable of breeding because both partners need to be sexually mature, fertile and receptive to mating
• form a pair bond that will lead to successful mating and raising of offspring
• synchronise mating so that it takes place when there is the maximum probability of the sperm and egg meeting
• become able to breed by bringing a member of the opposite sex into a physiological state that allows breeding to occur

Question 10

How is courtship behaviour used to determine where a female is in a receptive stage?

Answer 10

• females of many species undergo a cycle of sexual activity in which they can only conceive during a very short time
• often only receptive to mating for a period around the time when they produce eggs
• courtship behaviour is used by males to determine whether the female is at this receptive stage
• if she responds with the appropriate behavioural response courtship continues and is likely to result in the production of offspring
• if she is not receptive, she exhibits a different pattern of behaviour and the male ceases to court her, turning his attentions elsewhere

Question 11

How do animals communicate during courtship?

Answer 11

• during courtship, animals use signals to communicate with a potential mate and with members of their own sex
• typically there is a chain of actions between a male and female
• the chain of actions is the same for all members of a species but differs for members of different species
• in this way both individuals recognise that their partner is of the same species and that they may be prepared to mate

Question 12

What is artificial classification?

Answer 12

Artificial classification divides organisms according to differences that are useful at the time. Such features may include colour, size, number of legs, leaf shape etc. These are described as analogous characteristics where they have the same function but do not have the same evolutionary origins.

Question 13

What is phylogenetic classification?

Answer 13

• is based upon the evolutionary relationships between organisms and their ancestors
• classifies species into groups using shared features derived from their ancestors
• arranges the groups into a hierarchy, in which the groups are contained within larger composite groups with no overlap

Question 14

What are relationships in a phylogenetic classification partly based on?

Answer 14

Homologous characteristics, which have similar evolutionary origins regardless of their functions in the adult of a species.

Question 15

What is taxonomy?

Answer 15

• each group within a phylogenetic biological classification is called a taxon
• taxonomy is the study of these groups and their positions in a hierarchical order, where they are known as taxonomic ranks
• these are based upon the evolutionary line of descent of the group members
• a domain is the highest taxonomic rank and three are recognised: bacteria, archaea and eukarya
• dkpcofgs

Question 16

What features do bacteria have?

Answer 16

Bacteria are a group of single-celled prokaryotes with the following features:

• the absence of membrane-bounded organelles such as nuclei or mitochondria
• unicellular, although cells may occur in chains or clusters
• ribosomes are smaller (70S) than in eukaryotic cells
• cell walls are present and made of murein/peptidoglycan (but never chitin or cellulose)

Question 17

How do archaea differ from bacteria?

Answer 17

Archaea are a group of single-celled prokaryotes that were originally classified as bacteria which they resemble in appearance.

They differ from bacteria because:

• their genes and protein synthesis are more similar to eukaryotes
• their membranes contain fatty acid chains attached to glycerol by ester linkages
• there is no murein in their cell walls
• they have a more complex form of RNA polymerase

Question 18

What features do eukarya have?

Answer 18

Eukarya are a group of organisms made up of one or more eukaryotic cells. Their features are:

• their cells possess membrane-bounded organelles such as mitochondria and chloroplasts
• they have membranes containing fatty acid chains attached to glycerol by ester linkages
• not all possess cells with a cell wall, but where they do it contains no murein
• ribosomes are larger (80S) than in bacteria and archaea

Question 19

What is phylogeny?

Answer 19

The hierarchical order of taxonomic ranks is based upon the supposed evolutionary line of descent of the group members. This evolutionary relationship between organisms is known as phylogeny.

The phylogeny of an organism reflects the evolutionary branch that led up to it. The phylogenetic relationships of different species are usually represented by a tree-like diagram called a phylogenetic tree.

Question 20

Why is it difficult to define a species?

Answer 20

• species are not fixed forever, but change and evolve over time
• within a species there can be considerable variation among individuals
• many species are extinct and most of these have left no fossil record
• some species rarely, if ever, produce sexually
• members of different populations of the same species may be isolated, and therefore never got the opportunity to interbreed
• some types of organism are sterile

Question 21

What is molecular phylogeny?

Answer 21

The analysis of molecular differences in different organisms to determine the extent of their evolutionary relatedness is known as molecular phylogeny. The data obtained by molecular phylogeny has been accepted by scientists and this gave rise to new taxonomic groupings - all organisms can be separated into one of the three domains (most simple classification).

Question 22

How does the scientific community evaluate data?

Answer 22

• the findings are published in scientific journals and presented scientific conferences
• scientists then study the evidence in a process called peer review
• scientists start collecting evidence to either support or reject the suggestion