Download Natural Selection

Environmental Impact on
Phenotype
Section 8
Genotype, Environment &
Phenotype
• The final physical appearance (phenotype) of an
organism depends on the genetic information it
carries (genotype) and the environment it is in
• This can be summed up in the following word
equation:
Genotype + Environment
Phenotype
Genotype & Phenotype
• Some characteristics that are solely based
on genotype cannot be changed by the
environment e.g. Having a widow’s peak
Sunny climate
Rainy climate
Environment & Phenotype
• Other characteristics can be influenced by the
environment they are in.
• E.g. If you are genetically predisposed to being tall, but
you do not get enough food from your environment for
growth, you may end up being smaller than your full
potential
Twin Studies
• Identical twins are often used to determine the
effects of genotype and environment on the
physical appearance of an individual
• This is because identical or monozygotic twins
have the same genotype
Factors That are and are not
Inherited
• Genotypic traits are passed on to offspring
because DNA is passed on from each parent to
their child
• Environmental Factors ARE NOT passed on
from one generation to the next because they
usually do not help the species to evolve
• Environmental factors do not play any role in
natural selection
Natural Selection
An introduction
Charles Darwin
“The Origin of Species”
Variation in characteristics
• All individuals in a species are different from each
other.
• Some phenotypes are better suited to their
environment.
• More likely that organisms with these phenotypes will
survive to maturity and reproduce.
Environmental pressure
• Organisms produce more offspring than their environment
can support.
• Predation, competition, overcrowding and disease
resistance will limit the number of offspring surviving to
maturity.
Inheritance
• Offspring often resemble their parents.
• Beneficial characteristics are passed on
to offspring e.g. Ability to hide from
predators
End Result
• Process is repeated generation after generation.
• Organisms with the more favourable phenotype are
“selected” and survive.
• These organisms eventually become predominate in
the population.
• SURVIVAL OF THE FITTEST
Variation in characteristics
Environmental pressures.
Only those with favourable
characteristics survive.
Inheritance.
Favourable characteristics
passed on to offspring.
Organisms with most
favourable characteristics
predominant in environment.
Natural Selection
Process by which only organisms best
adapted their environment survive and
transmit their genetic characteristics
in increasing numbers to their
offspring while those less well adapted
tend to become eliminated.
Over to you
• Read “Environmental impact on phenotype”
• Do check test 8.1
• Read “Natural selection” and do activity 6.
• Do check test 8.2
Peppered moth
2 types
Pre industrial revolution
• Air clean
• Lichen light coloured.
• Light coloured moth less easily spotted by predators.
• More light coloured moths survived to pass genetic
information to offspring.
• Light coloured moth prevailed.
Post industrial revolution
• Air not as clean.
• Lichen and tree trunks darkened with soot.
• Dark coloured moth better adapted to environment.
• Dark coloured moth breeds and passes genetic
information to offspring.
• Dark coloured moth prevailed.
Summary
Before Industrial revolution
• Air clean
• Lichen light coloured.
• Light coloured moth less easily spotted by predators - they are
camouflaged.
• More dark coloured moths eaten by predators as easily seen.
• More light coloured moths survived to pass genetic information to
offspring
• Light coloured moth more common.
1840 – Industrial revolution
• Air not as clean.
• Lichens die.
• Light coloured moth spotted by predators as trees darker
• Dark coloured moth better adapted to environment.
• Dark coloured moth survives, breeds and passes genetic information to
offspring.
• Dark coloured moth more common.
Peppered moth game
• This link will allow you to be the bird
eating the moths!
Evolution
• The biodiversity of Earth is thought to have
occurred through a very slow process
known as evolution.
• Evolution takes millions of years and
involves the process of natural
selection.
Selective breeding
An example of artificial selection
New varieties of plants have
been produced through
selective breeding by man. Most
food plants bear little
resemblance to their original
wild variety.
Original wild variety of corn is shown
on the left of this picture, and
modern corn on the right. This was
achieved through many generations
of selective breeding.
Selective breeding in cabbage
plants
Wild cabbage
Modern crop plants have been
produced by selective breeding
Wheat
Barley
Potato
Plants have been selected for:
•Increased disease resistance
•Higher yield (of seeds, potatoes etc) per plant
Ornamental plants
Wild rose
Roses produced by selective
breeding from the wild rose
Plants are selected for:
•Scent
•Colour
•Stem length
•Shape
•Longevity
Selective breeding in farm animals
Wild ox ancestor
Modern cattle
Selective breeding has produced
many varieties of cattle
Selective breeding in dogs
Collie
Husky
Retriever
• Herding abilities
• Ability to pull a sledge
•Thick coat
• ability to find
and carry prey
All of these varieties of dog have been produced
by selective breeding over thousands of years
from their wild ancestor, the wolf.
Inbreeding regression
Inbreeding can sometimes cause problems!
Shar pei
Bull dog
– Have breathing difficulties
– Difficult to give birth naturally to offspring
Golden Retriever
• Hip dysplasia
• Hereditary cataracts
• Other eye conditions
Selective Breeding Notes
• Selective breeding is the deliberate
selection by humans of organisms which
have some benefit to humans.
• Organisms with desirable
characteristics are chosen to breed
• Undesirable organisms are not
permitted to breed.
Advantages of selective breeding
Characteristics which are often bred for
include:
–
–
–
–
Increased
Increased
Increased
Increased
milk yield in dairy cows.
beef yield in cattle.
disease resistance in crop plants.
yield in crop plants.
Disadvantages of selective
breeding
• Selective breeding takes a relatively
long period of time.
• Results are not always guaranteed as
there will always be some variation in
the offspring.
Genetic Engineering
Insulin Production
• Insulin is a hormone made by the body to
regulate the concentration of blood sugar.
• Diabetics are unable to produce this
hormone. This can be treated by taking
regular injections of insulin.
Insulin Production
• Insulin used to be extracted from pigs and
cattle for human use because the
hormone is similar, but not identical.
• Because the hormone is not exactly the
same, it could sometimes cause allergic
reactions.
• Producing insulin by genetic engineering
overcomes this problem.
Insulin Production
• The gene for human insulin has been
isolated and so the protein for insulin can
be made by genetic engineering
Bacterial
plasmids
Part of human
chromosome
Plasmid cut
open
Gene for insulin
cut out of
chromosome
Gene inserted
into plasmid
Plasmid
inserted into
bacterium
Large circular
chromosome
Notes!
• Using the previous diagram to help you,
describe in words how human insulin can
be produced by genetic engineering.
• List some advantages of genetically
engineered insulin.
Applications of Genetic engineering
Human
Growth
Hormone
Insulin
Factor VIII
Insulin
• Made by pancreas cells
• Diabetes: where insulin is not made or the
body doesn’t react properly to insulin
• Insulin given to diabetics
to relieve the symptoms of
diabetes
Better Blood
• Haemophilia is a condition where a person
is missing a vital protein to clot their blood.
• Genetic engineering can resolve this
potentially fatal problem.
• Genetically engineering blood proteins is
better than other treatments because there
is less risk of infections.
Human Growth Factor
• Made by cells in the pituitary gland.
• Required for children’s growth and
development.
• Given to children who cannot
make enough of their own.
Prevents reduced growth
and dwarfism.
Applications of genetic engineering
Product of genetic
engineering
Normal source and
function
Medical application
of gene
Insulin
Made by pancreas cells;
controls sugar levels in
blood
Given to diabetics who
cannot make insulin
Factor VIII
Chemical In blood;
require for blood clotting
Given by injection to
sufferers of Haemophilia
who lack Factor VIII and
whose blood fails to clot
Human growth hormone
Made by cells in pituitary
gland; Required for
children’s growth and
development.
Given to children who
cannot make enough of
their own.
Prevents reduced growth
and dwarfism
Fighting Disease
• Antibodies are the body’s natural defence
mechanism against foreign organisms
such as bacteria and disease
• Antibodies give us immunity – the ability to
protect ourselves from infection
• Oral vaccines are man made antibodies
(proteins) that are absorbed into the body
Fighting Disease
• Simple bacterial cells cannot be used to
make these oral vaccines because they
are too simple
• Plant and animal cells are used because
they can cope with making complex
proteins
Fighting Disease
Organisms which can produce
medically important proteins
Animals
Plants
Cattle
Soya Bean
Pigs
Maize
Sheep
Spinach
Goats
Tobacco Plant
Rabbits
Rubber Plants
Banana