Variation and Evolution Flashcards
what is variation
the differences in the characteristics of individuals in a population
what is natural selection
a process where organisms that are better adapted to an environment will survive and reproduce = advantahoues alleles are passed onto offspring
what are the causes of variation
alleles that individuals have inherited ( genetic variation eg eye colour)
environmental variation eg
variation of a combination of environment and genetic - height ( their genes might cause them to become taller but their diet eg calcium for bone development )
what are mutations
random changes to DNA
do mutations have any effect on phenotypes?
most of them dont but some can influence the phenotype eg an allele of tallness can lead to tallness if the person has a good diet
what is evolution
the change in the inherited characteristics of a population over time through a process of natural selection
what happens if 2 populations of one species became different in phenotype
they can no longer interbreed to produce fertile offspring and so the 2 populations become 2 separate species
what has the selective breeding of domestic dogs resulted in
to have a gentle nature
what has the selective breeding of food crops resulted in
selectively bred to be resistant to disease
what has the selective breeding of cows resulted in
selectively bred to produce more meat or milk
what has the selective breeding of certain plants resulted in to be advantageous
selectively bred to produce large or unusual flowers
what is selective breeding
the process where humans breed plants and animals for particular genetic characteristics
how is selective breeding carried out
- take the mixed population of desired characteristics from species and
choose parents organisms which show the desired characteristics - breed together
- From the offspring those with the desired characteristic are bred together
- This continues over many generations until all the offspring show the desired characteristics.
what is the natural selection process step by step
- variation exists as a result of genetic mutations
- some organisms are better adapted to survive in the environment ( survival of the fittest )
- they reproduce
- their alleles are passed onto their offspring
- when this process happens over many generations it results in evolution
what are the issues with selective breeding
if closely related animals are bred together then it results in inbreeding which can cause some breeds to be prone to disease or inherited defects
what are genes
sections of DNA on a chromosome
what is genetic engineering
process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
how have bacteria been genetically modified
genetically modified to contain useful substances eg human insulin gene which can be purified and used for type 1 diabetes
how have plants been genetically modified
- genetically modified to be resistant to disease or insect attack or even to create bigger more desirable fruits
what are advantges of GM crops/ plants
- produce greater yield that normal crops as they can be GM’d to produce larger and desirable fruits
- some GM crops are reistant to herbicides so farmers can spray their field and kill weeds without harming their crops
- GM crops produce scarce resources eg golden rice which provides as a source of vitamin A
- useful in medicine eg insulin producing bacteria t o overcome inherited disorders
what are the steps in genetic engineering
- identify gene that is wanted for transfer
- enzymes are used to isolate this gene
-transfer the gene into a vector this can be either small circle of DNA ( Plasmids ) or it can be transferred into a virus - the desired gene is transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
what is an advantages of cloning plants
effective way of producing new individuals from rare and endangered plants, helping to preserve the species.
- quicker to grow new plants
what is tissue culture
using small groups of cells from a part of a plant to grow identical new plants.
This is important for preserving rare plant species or cloning large numbers of plants / useful in commercial plant nurseries
what are cuttings
an older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
what are the steps for adult cell cloning
- The nucleus is removed from an unfertilised egg cell.
- The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.
- An electric shock stimulates the egg cell to divide to form an embryo.
- These embryo cells contain the same genetic information as the adult skin cell.
- When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
what are the issues with embryo transplants
- because you start with a sperm and an egg you cannot always be certain that the offspring will have the characteristics that we want
what is an advantage of adult cell cloning
- because we are cloning from an adult you know which characteristics the clone will have
why was Charles Darwins ideas on evolution not initially accepted
- the theory challenged the idea of creation
- there was insufficient evidence at the time the theory was published to convince many scientists
- the mechanism of inheritance and variation was not known until 50 years after the theory was published.
who was Charles Darwin
a scientist who proposed the theory of evolution by natural selection.
who was Jean Baptist Lamarke
scientist who suggested the theory that changes that occur in an organism during its lifetime can be inherited.
who was Alfred Russel Wallace
independently proposed the theory of evolution by natural selection.
who was Gregor Mendel
scientists who first discovered that inherited characteristics are determined by ‘units passed on unchanged
what are fossils
the ‘remains’ of organisms from millions of years ago, which are found in rocks.
what are the ways that a fossil can be formed
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- when parts of the organism are replaced by minerals as they decay
- as preserved traces of organisms, such as footprints, burrows and rootlet traces.
how can fossils decay
if there is a lack of :
- oxygen
-water
-if temperature is too cold
why is the fossil record incomplete
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.
what is extinction
Extinctions occur when there are no remaining individuals of a species still alive.
how can species become extinct
- due to catastrophic events eg an asteroid colliding with earth
- when the environment changes eg changing weather patterns
- a new disease/ new predator could kill all of the individuals of a species
- if a new, more successful species evolves and competes with the weaker species
Bacteria can evolve ?????because they reproduce at a ?????
rapidly , fast rate
how does antibiotic resistance happen
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.
what is an example of a bacteria that is resistant to antibiotics
MRSA
what are the ways to reduce the rate of development of antibiotic-resistant strains:
- doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
- patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
- the agricultural use of antibiotics should be restricted.
what is an issue with researches developing new antibiotics
is costly and slow. It is unlikely to keep up with the emergence of new resistant strains.
who is Carl Linnaeus
scientists who classified species into different categories depending on their structure and characteristics
what are the binomial categories that Carl Linnaeus made
- KINGDOM
-PHYLUM
-CLASS
-ORDER
-FAMILY
-GENUS
-SPECIES
how to do you find the actual name of a species
Organisms are named by the binomial system of genus and species. EG IF THE GENUS FOR A POLAR BEAR WAS URSUS AND THE SPECIES NAME WAS MARITIMUS THE POLAR BEAR SPECIES NAME WOULD BE URSUS MARTIMUS.
who is Carl Woese
scientists who developed the ‘three domain system’ who compared the biochemistry of different organisms
what is included in the three domain system
- Archae = primitive bacteria
- Eukaryota = animals/ plants/ fungi/ protists
what are evolutionary trees
method used by scientists to show how they believe organisms are related
what is genetic variation
- variations in the genotypes of organisms of the same species due to the presence pf different alleles this cause create differences in phenotypes
what causes genetic variation in species
- spontaneous mutations
- sexual reproduction
what are the types of gene mutation
- insertion
-deletion
-substitution
give examples of characteristics selected for in selective breeding
- disease resistance in corps
-higher milk or meat production in animals - gentle nature in domestic dogs
- large flowers
what are disadvantages of selective breeding
- Reduction in the gene pool ( which becomes especially harmful if sudden environmental change occurs)
- Inbreeding results in genetic disorders
- potential to unknowingly select harmful recessive alleles
what are the risks of GM crops
- Long-term effects of consumption of GM crops unknown
- negative environmental impacts, eg reduction in biodiversity , impact on food chain, contamination of non-GM crops forming ‘ superweeds”
- Late-onset health problems in GM animals
- GM seeds are expensive. LEDs’s may be unable to afford them or many become dependent on businesses that sell them
what is Bacillus thuringiensis ( BT)
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
- BT crops now secrete the toxin which kills any insect larvae that feed on it
what are the benefits of BT crops
- increases crop yields ( fewer crops damaged)
- 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 of BT crops are unknown
- Insect larvae may become resistant to the BT toxin
- Killing insect larvae reduces biodiversity
what is a vector
a structure that delivers the desired gene into the recipient cell eg plasmids and viruses
how can plants be cloned
- taking plant cuttings
- tissue culture
describe how plants are grown using tissue culture
- select a plant that shows the desired characteristic
- cut multiple small sample pieces from meristem tissue
- grow in petri dish containing growth medium
-transfer to compost for further growth
what must be ensure when preparing tissue cultures
ensure asceptic conditions to prevent contaminatino by microorganism
what does the growth medium contains
nutrient and growth hormones
what are 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 preservation of endangered plant species
what are the disadvantages of growing plats by tissue culture
- reduction in gene pool
- plant clones often have low survival rate
- could unknowingly increase presence of recessive alleles
describe the process of plant cutting method of plant cloning
- branch is cut off from parent plant
- the lower leaves of the branch are removed and the stem is planted
– pant hormones are used to encourage new root development
-plastic bag is used to cover new plant to keep warm and moist - new roots and new plant is formed after few week
