Topic 4 - natural selection and genetic modification Flashcards
What is evolution?
A gradual change in the inherited traits within a population over time
It occurs due to natural selection
Outline the theory of natural selection
1genetic variation exists due to spontaneous mutations
- Selection pressures (e.g competition, disease) exist
- Random mutation gives an organism a selective advantage
- The organism is better adapted to the environment and survives
- The organism reproduces, passing on its beneficial alleles
- The frequency of the advantageous alleles increase
Why does competition between organisms in a habitat exist?
The resources within a habitat required for survival are limited
Give some examples of competition between organisms within a habitat
Competition between animals for food, shelter, mates etc.
Competition between plants for light, water, minerals etc.
Describe how antibiotic resistance in bacteria can be used as an example to illustrate the process of evolution
- Genetic variation exists due to spontaneous mutations
- Antibiotics act as a selection pressure
- Mutations gives a bacterium antibiotic resistance
- If an antibiotic is administered, the bacterium is better adapted and survives, whilst other bacteria are killed
- Bacterium reproduces, passing on its resistant variant
- Frequency of antibiotic resistant allele increases
Why is the development of antibiotic resistance in bacteria a good study for evolution?
Bacteria reproduce very rapidly, allowing the first hand observation of evolution
How can the observation of fossils provide evidence for evolution?
Older fossils contain simpler organisms
Newer fossils contain more complex organisms
Comparisons of fossils show that simple organisms evolved into more complex life forms
Fossils can be organised into chronological order, allowing the changes in organisms over time to be observed
Describe the role of Darwin in the development of the theory of evolution by natural selection
He studied a variety of organisms whilst travelling around the world on the HMS beagle
He noted that traits can be passes from parents to offspring
He proposed the idea of ‘survival of the fittest’
He established the theory of natural selection and published his ideas in ‘on the origin of species’
Describe the role of Wallace in the development of the theory of evolution by natural selection
He proposed a theory of natural selection to Darwin’s, although the me Hanson’s were different
He gathered greater evidence to support the theory
How has the theory of evolution by natural selection impacted modern biology and society?
It enables the classification of organisms
Influences modern medicine by emphasising the importance of finishing antibiotic treatments and the need for the constant production of new antibiotics
Highlights the importance of high genetic diversity in habitats which aids conservation projects
What fossils have provided evidence for human evolution?
‘Ardi’ - 4.4 million years ago
‘Lucy’ - 3.2 million years ago
Leaky discovered 1l6 million year old fossils
What clues does ‘Ardi’ give scientists about human evolution?
She shows phenotypic traits which encompass characteristics of both humans and apes
Ape like characteristics: long arms, large big toes
Human like characteristics: the structure of her bones suggests that she walked upright
What clues does ‘Lucy’ give scientists about human evolution?
She shows phenotypic traits which are more human like than that or ‘Ardi’
The structure of bones in her legs and feet are more adapted to walking than climbing
Her brain size is closer to that of an ape’s
How did Leakey’s findings provide evidence for human evolution?
He discovered many hominid fossils
The 1.6 million year old fossil ‘Turkana boy’ showed traits comparable to that of modern day humans e.g. similar brain size
How has the development of stone tools provided evidence for evolution?
Correlation between the development of more complex tools and an increase in brain size
Primitive tools are older than more complex tools. Brain size has increased over time, as it increased advancements in tool use were made
Describe the methods used by scientists to date tools
Carbon-14 dating - estimating the age of carbon containing material that is found in tools or alongside tools
Stratigraphy - using the age of the layers of sediment surrounding the tool as an induction of the age of the tool
What is a pentadactyl limb?
A limb with five digits present in animals, birds, reptiles and amphibians
How does the pentadactyl limb provide neidende for evolution?
The presence of the pentadactyl limb suggests that all species which possess it have descended from a common ancestor
What is classification?
The organisation of organisms into groups
What is taxonomy?
The classification of organisms into taxa: kingdom, phylum, class, order, family, genus, species
Name the five kingdoms
Animals, plants, fungi, protists, prokaryotes
What happens to the number of organisms in each Taxon as you move down the hierarchy?
The number or organisms decreases
Traditionally, organisms were grouped based on similarities and differences in their anatomy and behaviour. What is the problem with this?
Organisms that are not closely related may look alike and behave similarly if they live in the same environment
Some closely related species may look very different is they like in different environments
What advancements in science have led scientists to reconsider the five kingdom classification system?
Microscopes
Biochemistry
DNA and RNA analysis
Describe the three domains system of classification
Organisms are intially divided into theee groups: archaea, bacteria, eukarya
So the taxa system then goes; domain, kingdom, phylum, class, order, family, genus, species
Which domain do eukaryotic organisms belong to?
Eukarya
Which domains do prokaryotic organisms belong to?
Archaea and bacteria
Describe the domain bacteria
It consists of true bacteria
Describe the domain archaea
Consists of primitive microorganisms Contains extremophiles (adapted to live in extreme conditions)
What is elective breeding?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
Outline the main steps involved in selecting breeding
- Identify a desired characteristic
- Select parent organisms that show the desired traits and breed them together
- Select offspring with the desired traits and breed them together
- Process repeated until all offspring have the desired traits
What is the main advantage of selective breeding?
It creates organisms with desirable features
Other than in agriculture, where else is selective breeding useful?
In medical research In sports (horse racing)
Outline the disadvantages of selective breeding
Reduction in the gene pool Inbreeding results in genetic disorders Development of other physical problems Develops other physical problems Potential to unknowingly select harmful recessive alleles
How can plants be cloned?
Taking plant cuttings
Tissue culture
What is tissue culture?
A method of growing living tissue in a suitable medium
Describe how plants are grown using tissue culture
Select a plant that shows desired characteristics
Cur multiple small sample pieces from meristem tissue
Grow in a Petri dish containing growth medium
Transfer to compost for further growth
What must be ensured when preparing tissue cultures?
Ensure aseptic conditions to prevent contamination by microorganisms
What does the growth medium contain?
Nutrients and growth hormones
What are the advantages of growing plants by tissue culture?
Fast and simple process
Requires little space
Enables the growth of many plant clones with the same desirable characteristics
Useful in the preservation of endangered plant species
What are the disadvantages of growing plants by tissue culture?
Reduction in the gene pool
Plant clones often have a low survival rate
Could unknowingly increase the presence of harmful recessive alleles
Why is animal tissue culturing useful?
In the preparation of tissue samples for medical research
Enables the investigation of how different factors may affect a specific animal tissue, without harming the animal itself
Describe how animal tissue cultures are prepared
Extract a sample of tissue from an animal
Use enzymes to separate cells within the sample
Grow in a culture vessel containing growth medium
Once grown, store the sample
What is genetic engineering?
The modification of the genome of an organism by the insertion of a desired gene from another organism
Enables the formation of an organism with beneficial characteristics
Describe the process of genetic engineering
DNA is cut at specific base sequences by restriction enzymes to create sticky ends
Vector DNA is cut using the same restriction enzymes to crease complimentary sticky ends
Ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DBA
Recombinant DNA mixed with and ‘taken up’ by target cells
What is a vector?
A structure that delivers the desired gene into the recipient cell e.g. viruses
Describe the benefits of genetic engineering
Increased crop yields for growing population
Useful in medicine
GM crops produce scarce resources
Describe the risks of genetic engineering
Long term effects of consumption of GM crops unknown
Negative environmental impacts
Late onset health problems in GM animals
GM seeds and expenseive
What is Bacillus thuringiensis (by)?
Insect larvae are harmful to crops
BT is a bacterium which secretes a toxin that kills insect larvae
How is genetic engineering used to protect crops against insects?
The gene for toxin production in Bt can be isolated and inserted into the DNA of crops
But crops now secrete the toxin which kills any insect larvae that feed on it
What are the benefits of the crops?
Increased crop yields
Lessens the need for artificial insecticides
Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it
What are the risks of Bt crops?
Long term effects of consumption unknown
Insect larvae may become resistant to the toxin
Killing insect larvae reduces biodiversity
Outline the agricultural methods of increasing food production
Intensive farming methods e.g. battery farming and the use of fertilisers and pesticides
Biological control
What is the main advantage of intensive farming?
Increases crop yields
What are the disadvantages of intensive farming methods?
Fertilisers can wash into nearby water sources and cause eutrophication
The use of herbicides and insecticides reduces biodiversity
‘Battery’ farming is often seen as unethical
What is biological control?
When a new organism is introduced into an ecosystem to control a pest or pathogen
What are the advantages of using biological control to increase food production?
The results generally last for a long period of time
The effects on wildlife are less severe
What is the risk of biological control?
Risk of the control organism becoming a pest itself
