Bio Exam

(a) (i) State a form of evidence which is commonly used to construct cladograms.

(a) (i) State a form of evidence which is commonly used to construct cladograms.

base sequences of genes OR amino acid sequence of proteins

(ii) Define the term clade.

a group of organisms which share a common ancestor

(b) Describe the structure of cladogram.

• root as the initial ancestor common to all organisms in the cladogram

• node as a common ancestor shared between two or more organisms in a cladogram

• terminal branch as representing a species within the cladogram

(a) (i) State a way in which the genome within a species can vary.

base sequence of DNA can vary OR single-nucleotide polymorphisms can cause variation

(ii) Describe the current and one future application of genome sequencing.

• research into evolutionary relationships OR constructing cladograms OR molecule clocks OR other current application

• personalised medicine OR other future application

(b) Define the biological species concept.

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

(a) (i) Carbon dioxide is a greenhouse gas. State the names of two other greenhouse gases.

• Carbon dioxide

• Methane

(ii) Describe how deforestation causes an increase of carbon dioxide in the atmosphere.

• Fewer trees to absorb CO2 and use it in photosynthesis

• Use in manufacturing

(b) As snowfall is reduced due to increasing temperatures, less water runs off mountains resulting in less water available for forests. Explain how this leads to forest browning.

• Water required for photsynthesis in trees

• less photosynthesis occurs when less water available

• leaves turn brown and fall from the trees

(c) Describe why the loss of boreal forests is an example of a tipping point.

Forest changes from a carbon source to a carbon sink.

(d) Suggest two ecological strategies that could help to slow the rate of global warming.

• Afforestation

• Reforestation

(a) (i) Outline two adaptations of the desert hedgehog that allow for it to survive.

• Large ears

• Spikes

• Long legs

• Camouflage color

(ii) Explain how natural selection has selected for the adaptations outlined in (a) (i) .

• Variation in a population

• Allele giving individuals an advantage; they survive and reproduce

• Passed to offspring and frequency of advantageous allele increases

(b) (i) Define geographic isolation.

When a population is isolated by physical barriers, i.e. new river or mountain

(ii) If populations of species become isolated for long periods of time, speciation may occur. Define speciation.

Emergence of a new species

(iii) Explain how scientists could investigate if speciation has occurred.

Allow an organism from each population to breed; if offspring are fertile; they are both the same species; accept reverse arguments.