No two people are exactly the same. How is this possible?

The current population of planet Earth is more than 7 billion people!

Learning Objectives

Define the term variationDiscuss the fact that variation occurs within as

well as between speciesDescribe the differences between continuous and

discontinuous variationExplain both genetic and environmental causes of

variationOutline the behavioural, physiological and

anatomical adaptations of organisms to their environment

Success criteria

To understand the variation in living organisms and how they are adapted to their environment

Variation Variation can be described as differences that

exist between individuals. There are 2 types

Interspecific – between different species

Intraspecific – within a species

Like all babies, this little boy carries a unique set of genes, half from his mother and half from his father.

This newborn baby’s characteristics are passed in the genes it has inherited from its parents.

Activity: VariationList 4 ways how sexual reproduction

produces genetic variation amongst a species

Variation4 ways how sexual reproduction produces

variation amongst a species:Random matingRandom fertilisation of gametesIndependent assortment of chromosomes (and

therefore alleles) during meiosisMutation - cause a change in genes giving rise

to new alleles and changes in phenotype

But are your characteristics only affected by your genes?

What else will influence the characteristics of this baby as he grows up?

People are different because they inherit different characteristics from their parents.

Environment

Causes of variation

Your upbringing and the environment in which you live also affect how you turn out as an adult!

When he gets older, this baby might support a different football team (like Fulham) or not even like football.

Environmental VariationExamples in which Environment effects

amount of growthAmount of food availableAmount of water availableExposure to sunlightStrong prevailing wind to trees

Differences in some characteristics are due to a combination of both inherited and environmental factors.

Name three examples of this type of characteristic.

Your unique characteristics are caused by:

- the unique set of genes you have inherited from your parents

- the environment in which you have developed.

Be careful when drawing conclusions about the causes of variation.Eg Overeating

•Once thought only to be caused by environmental factors eg increased availability of food in developed countries.•Later discovered that food consumption increases dopamine levels, once enough dopamine was released eating would stop.•Researches discovered that people with one particular allele has 30% fewer dopamine receptors.•Therefore people with this particular allele were more likely to overeat.

Characteristics can be classified in different ways.

How would you categorize variation in eye colour?

Could you categorize variation in height in the same way?

Variation in eye colour can be easily categorized in distinct groups. You either have a certain eye colour or you don’t.

Height variation doesn’t fall into separate groups, as it covers a range of values.

A feature that can be measured and given a value

from a range of values shows continuous variation .

A feature that cannot be measured but is one of a few distinct options shows

discontinuous variation.

Which type of variation are eye colour and height?

Characteristics can be classified into two types:

This type of feature varies over a continuous range of values.

Examples of continuous variation include mass, height, skin colour, intelligence and leaf area. Continuous variation is due to the combined effects of a large number of genes and the environment.

Does this mean the value of such a feature is fixed or can it change?

Bar chart to show the range of masses in a rugby team

70 80 90 100 110 120 1300

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2

1

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mass (kg)

nu

mb

er

of

rug

by

pla

yers

What is continuous variation?

This type of feature can only be one of a few distinct options. Either you have this type of characteristic or you don’t.

Examples of discontinuous variation include blood group, natural eye colour and inherited diseases.

Discontinuous variation is controlled by a small number of genes with little environmental influence.

Bar chart to show the frequency of blood groups in a rugby team

O A B AB0

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blood group

nu

mb

er o

f ru

gb

y p

laye

rs

Does this mean the value of such a feature is fixed?

What is discontinuous variation?

Variation exam questionMay 2012 Q3 – see folderAnswersb)i. Pipistrellus ;b)ii.1. similar / same, (body) mass ;2.similar wingspan ;3.`similar / same, colour ;4.all characteristics , similar /

same, except echolocation /wingspan ;

5.previously unable to measure echolocation (frequency) ;

b)ii.Mark the first answer. If the answer is correct and anadditional answer is given that is incorrect or contradicts thecorrect answer then = 0 marks1.IGNORE ‘similar appearance ’ACCEPT ‘both 5.5 g’2.IGNORE ‘same’ ACCEPT ‘almost the same’ or ‘small difference’ or ref to figures3.ACCEPT ‘both (medium to dark) brown’

Variation exam questionb)iii.1.genetics / genes / DNA ;

2.RNA ;

3.amino acid sequences ;

4.cytochrome C / fibrinopeptide ;

Mark the first two answers only.1 IGNORE chromosomes1 ACCEPT (named) bases

1 or 2 CREDIT ‘nucleotide sequence / polynucleotide base sequence’ for 1 mark if neither of mp 1 nor mp 2 have been awarded

3 ACCEPT primary structure of polypeptide

4 ACCEPT haemoglobin

Variation exam questionb)iii.1. genetics / genes / DNA ;2. RNA ;3. amino acid sequences ;4. cytochrome C / fibrinopeptide ;

b)iv.1. (inter)breed / AW ;2. determine if offspring are fertile ;3. if offspring are infertile / no

offspring produced, then different species ; ora

Mark the first two answers only.1 IGNORE chromosomes1 ACCEPT (named) bases1 or 2 CREDIT ‘nucleotide sequence / polynucleotide base sequence’ for 1 mark if neither of mp 1 nor mp 2 have been awarded3 ACCEPT primary structure of polypeptide4 ACCEPT haemoglobin

1. ACCEPT ‘mate’ / ‘reproduce’CREDIT ‘observe to see if populations are reproductively isolated’ as resitting A2 candidate might consider phylogenetic species definition2. This mark is for assessing the fertility of the offspring3. 'if they belong to the same species they will be able to breed with each other and produce fertile offspring' = 2 marks (1stand 3rd)

Adaptation Key Term: Adaptation

A feature that enhances survival and long term reproductive success

Adaptations help organisms to cope with environmental stresses and obtain the things they need to survive

What will a well adapted organism be able to do?

AdaptationWhat will a well adapted organism be able to

do?

Find enough food, photosynthesise wellFind enough waterGather enough nutrientsDefend itself from predators and diseaseSurvive the physical conditions of it’s

environment eg temperature and lightStill have enough energy to reproduce

Adaptations Behavioural Adaptations

Aspect of behaviour that helps organism surviveE.g. earthworm withdraws into burrow when

touchedPhysiological Adaptations

Ensure correct functioning cell processesE.g. yeast making correct enzymes to respire

Anatomical (structural) AdaptationsStructure that aids survivalE.g. flagella allowing bacteria to move

HomeworkPrepare a poster/leaflet on the different

adaptation of xerophytic plants