Variation and evolution

3 Fctors which effects (phenotypic) variation

1. Genetic factors (differences in the alleles individuals inherit)
2. Environmental factors (differences in the conditions in which individuals develop)
3. A combination of genetic and environmental factors

what is the impact of mutation in the phenotype of the organism?

* **Mutations occur continuously.**


* Very rarely will a mutation lead to a new phenotype.
* If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species as they will breed more frequently.

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* For example:
* A moth develops a **mutation** leading to a change in its color
* This makes it blend in better with the tree bark it lives on and **less visible to predators**
* This moth has a **survival advantage** and **breeds more frequently**, increasing its chances of passing on the mutated phenotype to the next generation
* The new color quickly spreads throughout the species

how is there an extensive genetic variation within a population of a species?

* There is usually extensive genetic variation within a population of a species
* All genetic variants arise from **mutations**
* Mutations are **random genetic changes** that occur continuously

What is the process of genetic modification?

1. the gene needs to be identified.
2. Enzymes are used to isolate (cut out) the desired gene.
3. The gene is inserted to a vector (usually a virus or a becterial plasmid)
4. The vector is used to insert the gene into cells of reciptent organisms
5. The gene is transferred at an early stage of development of the reciptent, so that the new gene will now be copied into all new cells as the organism grows

Main steps in genetic engeneering.

In genetic engineering:

• enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus

• the vector is used to insert the gene into the required cells

• genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics

Reasons why selective breeding is used

1. disease resistane
2. improved yields
3. variation in species
4. domesticating animals

genetic engineering in crops; mention 6 reasons.

1. Increased yield e.g. bigger fruit 
2. Increase quality e.g. better taste 
3. Resistance to disease 
4. Resistance to insects  
5. Resistance to herbicides  
6. Resistance to droughts  

How do genes and environment together effect the growth?

**genes decide what characteristics we inherit**, the surrounding **environment will affect how these inherited characteristics develop**

Write the format of the answer to the question :

explain how evolution occurs through natural selection which results in an animal….

There is variation among the ____ population so some can …..

A mutation arises that allows ___ to ……..

Those _____ that can ……… are more likely to survive

and are therefore more likely to reproduce and pass on their advantageous alleles 

This repeats over multiple generations 

So the advantageous allele spreads throughout the population, until the species has 'evolved' to ……….

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There is variation among the zebra population so that some can run faster than others 

A mutation arises that allows some zebras to run faster

Those zebras that can run fastest are more likely to survive... 

...and are therefore more likely to reproduce and pass on their advantageous alleles 

This repeats over multiple generations 

So the advantageous allele spreads throughout the population, until the species has 'evolved' to run faster

What to always write in an exam question asking about selective breding

**selective breeding process for many generations**

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(selecting two parents with desired characteristics, breeding them and stopping there is not selective breeding and will not give rise to a new breed.)

drawbacks of inbreeding

* Rare inherited diseases are more likely to appear
* The population as a whole will be more at risk of disease 
* It reduces that size of the gene pool 

How have bacterial cells been genetically engeneered to benefit us?

They have been genetically engineered to produce useful substances such as human insulin to treat diabetes.

Describe the process of selective breeding

* Selection of parents with desired characteristic
* Selected parents are bred together to produce offspring
* Offspring with desired characteristic are selected and bred
* Process is repeated over many generations (until offspring have desired characteristics 

Concerns about GM crops.

* the effect on populations of wildflowers and insects.
* Some people feel the effects of eating GM crops on human health have not been fully explored.

What are the 3 ways in which fossils are formed?

* From parts of an organism that have not decayed because one or more of the conditions needed for decomposing was absent. *(lack of moisture/oxygen, too acidic, too cold for decomposers to survive)*

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* when minerals replace parts of the organism as they decay *(teeth, shells, and bones)*

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* as preserved traces of organisms, such as footprints, burrows, and rootlet traces. (*impressions on a soft material like a clay)*

Why are scientists not sure on how life began on earth?

Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.

geological reasons in which populations of a species can become isolated

•Land mass breaks off / formation of an island

•Flooding

•Formation of a new mountain range

reasons why a species may become extinct.

•changes to the environment over geological time

•new predators

•new diseases

•new, more successful, competitors

•a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids

Why can bacterias evolve fast?

They evolve rapidly because they reproduce at a fast rate

How does antibiotic resistance occur?

* Mutations of bacterial pathogens produce new strains.
* Some strains might be resistant to antibiotics, and so are not killed.
* They survive and reproduce, so the population of the resistant strain rises.
* The resistant strain will then spread because people are not immune to it and there is no effective treatment.

How can doctors reduce antibiotic resistance?

* Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections

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* Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains

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* The agricultural use of antibiotics should be restricted.

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Why is it unlikely to keep up with the emergence of new resistant strains?

* The development of new antibiotics is costly and slow