biodiversity And Classification

Question 1

Homologous structures

Answer 1

Common origin,
PENTADACTYL LIMB!!!!!
different purpose but common ancestor

Question 2

Divergent evolution

Answer 2

Common origin different functions

Question 3

Analogous structure

Answer 3

No common ancestor similar function

Question 4

Convergent evolution

Answer 4

Development of similar structures in unrelated organisms over long periods of time due to natural selection of similar features in a common environment

Question 5

Polymorphism

Answer 5

is the presence of more than
one form or type of organism within a single
species. This is the result of multiple alleles for a gene. It is assessed by determining the number of alleles and the proportion of individuals with that allel

Question 6

Biodiversity

Answer 6

Biodiversity refers to the number of different species
(species richness) and the number of individuals of each
species (species evenness) in a given environment.
Biodiversity varies spatially – the closer to the equator, the
more biodiversity there is.
Biodiversity varies temporally – through time biodiversity
has varied, e.g. mass extinctions reduce biodiversity. Human activities affect biodiversity, e.g. through habitat destruction and climate change.

Question 7

Assessing biodiversity in field work

Answer 7

Grid an area and use a random number generator to
select co-ordinates at which to place quadrats. This
avoids bias.
•Count the number of different species and the number
of individuals of each species in the quadrat.
•Repeat 10 times to improve reliability.
•Calculate Simpson’s diversity index using the formula:
D = 1–
Σn(n–1)
N(N–1)
where N = the number of different species and
n = the number of individuals of each species.
Simpson’s diversity index reduces species richness and
evenness to a single number so that different areas can be
compared.Kick sampling can be used in rivers and the Lincoln index can be used to estimate populations of mobile organisms.

Question 8

Natural selection leads to adaptations like?

Answer 8

organisms being adapted to their environment.
Adaptations can be morphological, physiological or behavioural. In a desert environment, the extreme temperature fluctuations and aridity have led to the
jerboa (a small, hopping rodent) having:
•large ears to aid heat loss (morphological adaption)
•a long loop of Henle to reabsorb the maximum volume of water from
urine (physiological adaption)
•crepuscular activity (dawn and dusk), burrowing to avoid the heat of the day and cold nights (physiological adaption).

Question 9

natural selection

Answer 9

All individuals in a species have genetic variation (through
mutation) that can be inherited.
•Some variants have a selective advantage, e.g. if a selection
pressure is predation, a better camouflaged individual has an advantage over a less well camouflaged one.
•These variants survive, reproduce and pass their advantageous alleles to their offspring.

Question 10

Analysis of organisms

Answer 10

Counting every allele in a population is difficult. Analysis of base sequences in DNA can be carried out on samples of the population to look for variation between individuals. The larger the variation, the higher the genetic diversity.

Question 11

Classification

Answer 11

Classification is the division of living organisms into groups based on their evolutionary
relationships. Classification is hierarchical, meaning that large groups are split into groups of
decreasing size. Classification is phylogenetic, meaning that organisms in the same group are more closely related. As the groups are discrete, an organism cannot belong to more than one group at the same taxonomic level. Each group is called a taxon.

Question 12

The taxonomic groups are:

Answer 12

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 13

The five kingdoms:

Answer 13

Prokaryotae
animalia
plantae
Fungi
Protoctista

Question 14

The three domains are:

Answer 14

Eubacteria – these are the ‘true’ bacteria
Archaea – these are also prokaryotic but are extremophiles
Eukarya – these are all the eukaryotic organisms.
Extremophiles live where environmental conditions are
harsh, e.g. in very high or low temperatures (thermophiles orpsychrophiles), in acidic or very alkaline environments, and in areas with high salinity (halophiles) or high pressure.

Question 15

Establishing relatedness

Answer 15

Morphological evidence
Biochemical evidence

Question 16

Morphological evidence

Answer 16

Morphology means looking at the shape and form of an organism.
Some organisms have similar morphology but are unrelated in evolutionary terms – this arises by convergent
evolution. An advantage of using biochemical analysis such as DNA sequencing is that it can overcome issues
caused by convergent evolution.
The underlying form of organisms provides evidence of relatedness.
Homologous structures have the same structure but different functions. An example of a homologous structure is
the pentadactyl (literally five-fingered) limb. The underlying structure is the same in mammals, birds, reptiles and
amphibia but the function is different. Homologous structures indicate that organisms are related.
Analogous structures arise through convergent evolution, the function is the same, the origin of the structure is
different. A good example of this is the wings of birds and insects. In birds, the wing is a modified bony pentadactyl
limb; in insects, the wing is supported by veins and has arisen from a different structure.

Question 17

Biochemical evidence

Answer 17

Biological polymers that have subunits which are different, such as DNA,
RNA or protein, can be used to establish relatedness. The sequences of
subunits can be compared and the number of differences counted. The
more differences there are in sequence, the less closely related two
organisms are.
Differences in sequence are owing to mutations. Mutations in DNA can
lead to differences in the amino acid sequence of proteins. Depending
on the organism type and reproduction rate, it is possible to use these
differences to construct a ‘molecular clock’ which shows how long ago
that mutation occurred. This means that a timeline can be drawn as to
when a species or group diverged.
Fragments of DNA and proteins can be separated by gel electrophoresis. The gel allows small fragments to move further, and the electrical charge causes movement of the negatively charged fragments to the positive electrode. A banding pattern is produced, called a DNA fingerprint, which can be used for comparison. Alternatively, sequences of DNA and amino acids can be established.

Question 18

Phylogenetics trees

Answer 18

diagrams that represent the evolutionary pathways leading to different species. The axis is time, which moves forward the further up the tree branches you go. Each junction representsa common ancestor for the branches. The more recent a common ancestor, the more closely related the
organisms are.