Evolution Flashcards
Variation
Differences in characteristics of individuals in a population
3 causes of variation in any population
-Inheriting different alleles from parents like hair colour
-Environment changes like colours of flower due to soil
-Combo of environment + genetics like height
What causes the genetic variation in species?
Mutations or random changes in DNA
Types of mutations
-No effect on the phenotype
-Influence the phenotype under certain circumstances
-Completely determine the phenotype (rarely)
How do mutations effect a population?
If the environment changes
A mutation could help them survive or resistant to change
Thus the surviving organisms will have a different phenotype
And will be inherited by all other organisms
Which is the baseline for evolution
How have different species come to be on earth?
All have evolved over very long period of time from simple single cells
Through evolution by natural selection
Stages of natural selection aka evolution
Species have a lot of genetic variation for diff phenotypes
If the environment changes, those with alleles to adapt to this change more likely to survive
Thus more likely to reproduce
And their offspring could inherit this allele then reproduce
Thus over time the whole population will have this phenotype
Evolution
The change in inherited characteristics of a population over time through natural selection
How does an animal differentiate into 2 different species?
If 2 populations of species become so different in phenotype over a period of time
Due to evolution
That they can no longer interbreed and produce a fertile offspring
= 2 separate species
Selective breeding
When humans decide which animals/ plants with a specific phenotype to breed in order to get an offspring with a desired phenotype
Pretty much speeding up the process of evolution but so they’re more useful to us
Examples of selective breeding
Dogs = more gentle nature
Crops = disease resistance
Cattle = more milk/ meat
Plants = large flowers
Stages of selective breeding (cows for meat)
Take mixed population of cows and select largest male + female
Breed them
Sexual reproduction = variation so some offsprings don’t have desired characteristic
So select the largest male and female offspring from that
Breed them
Repeat for many generations until all offsprings are large
Big problem with selective breeding
Breeding closely related animals/plants = inbreeding
Which cause being prone to disease or inherited defects
Genetic engineering
When a gene from one organism with a specific characteristic
Is taken from an organism
And transferred to another when in development so it has that characteristic
Using genetic engineering for type 1 diabetes
Putting the insulin producing gene in bacteria from a human
Then purified
So it produces insulin
Thus can help treat type 1 diabetes
Genetically modified
When you transfer a human gene to an organism to make it carry out a specific function/ have a specific characteristic
Why would we genetically modify crops?
Produce a greater yield
Resistant to disease/ insects
Produce bigger fruits
Resistant to herbicides so farmers can kill weeds but not harm the crops
Disadvantages of genetically modified crops?
Possibly harm insects
Or wild flowers
Health effects if humans eat it needs more research
Gene therapy
Using genetic modification to cure inherited disorders in humans
Disadvantages of gene therapy
We don’t know long term effects
Don’t know if it has effects on other genes
Steps of genetic engineering
Identify gene we want to transfer (from animal/human/plant)
Use enzymes to isolate it
Transfer gene into a circle of dna called plasmid from bacteria, or into a virus
Desired gene is transferred into target organism
Vector
The plasmid or virus that transfers the DNA from one organism to another
In genetic engineering Why do we transfer gene at an early stage in the target organisms development?
Make sure all cells receive the transferred gene
So the organism develops with this characteristic
Clone
Organism genetically identical to its parent
Advantages of cloning plants
Because it’s genetically identical to parent we know what it’s characteristics will be
Cloning plants using cuttings
Take small cutting of plant
Dip the end in rooting powder
Thus the plant develops roots
And is genetically identical
What method to get hundreds of clones of a plant?
Tissue culture
Tissue culture stages
Take parent plant
Divide into many small pieces
Containing small number of cells
Incubate with plant hormones
So the plant is stimulated to grow and develop fully grown clones
Conditions for tissue culture
Sterile
So we don’t have any microorganisms like bacteria or fungi
Adv of tissue culture
Thousands of genetically identical plants quick and cheap (commercially)
We can be certain of characteristics
Preserves rare species
Who began classifying species?
Carl Linnaeus
Classification system Linnaeus developed
2 kingdoms: plant and animal
Each then divided into smaller categories
What were the smaller categories Linnaeus developed?
Kingdom
Phylum
Class
Order
Family
Genus
Species
How to remember smaller categories Linnaeus came up with
Kingdom = King
Phylum = Philip
Class = Came
Order = Over
Family = For
Genus = Good
Species = Soup
Binomial name system
Species name is:
Genus + species
Eg homo sapien
What is Linnaeus system based on?
Characteristics we can physically see
Why did Linnaeus system change
Advances in science so we don’t have to base it on what we see
We can use tech to Analyse dna
What classification system is used now?
Three domains
Who came up with three domain system
Carl woese
What’s in the 3 domain system?
Archae (primitive bacteria) in hot springs
True bacteria (in our bodies)
Eukaryota (animal, plants, fungi, protists, amoeba)
How can we tell how closely related species are?
Evolutionary tree
The length of time goes up the scale at the side
How to make an evolutionary tree?
Use classification data on living ones like dna
But if it’s extinct we use fossils
Problem with evolutionary tree
Extinct creatures can only be judged on fossils
But records of fossils for some are incomplete
How do evolutionary trees work?
Where it crosses = common ancestor
Fossils
Remains of organisms from millions of years ago in rocks
How can fossils form?
If conditions for organism to decay aren’t there thus it doesn’t ie too cold, no oxygen or water
If the organism decays but is replaced by minerals
By traces of organisms like footprints
Problem with fossils
Most organisms didn’t have skeleton (soft body)
And didn’t form fossils
And the ones that did were destroyed due to changes in earths crust
What do fossils show
Huge number of species that have been extinct
Ways of cloning animals
Embryo transplants
Adult cell cloning
Embryo transplant stages
Sperm and egg cell from target mammal with desired characteristics
Produces fertilised egg
Develop into early stage embryo
Use glass rod to split in 2
Transplant this into 2 host mothers to give birth
Therefore have 2 identical offspring = clones
Why must we separate an early stage embryo into multiple embryos during embryo cloning?
So the cells don’t specialise into specialised cells before they can be split
Problem with embryo transplants
Because it undergoes fertilisation in sexual reproduction, we can’t be certain it has desired characteristics as it’s varied
How can we overcome the problem with embryo transplants?
Use adult cell cloning instead
Benefits of adult cell cloning
Cloning from an adult = we know what characteristics it will have
Stages of adult cell cloning
Take cell from target animal
Remove nucleus
Take unfertilised egg cell from same species
Take the nucleus out of this egg cell and throw it away
So we insert nucleus from original target animal cell
So now it only contains genetic info from target animal
Give it an electric shock so it divides = embryo
As the embryo develops, put in host mother to continue development
Why does the host mother and clone look different in adult cell cloning?
Because we are NOT cloning the host mother!!!!
She is acting as a surrogate to give birth to it and provide it with what it needs
We are cloning a different animal
Evolution by natural selection (triple science)
In a species there is lots of genetic variation for characteristic
Ones with characteristics most suited to environment can breed most successfully
So the useful characteristic could be passed to next generation
On the origin of species
Darwin’s theories of evolution published book
Origin of species book reception at the time
Very controversial
Only became gradually accepted
Why was Darwin’s work not accepted at first?
Strong belief god made everything
Some felt he did not have enough evidence
Not understanding of how things are inherited
Jean baptise Lamarck theory
If characteristic is regularly used it develops more thus passes to its offspring
Problem with Lamarcks theory
Changes due to environment are not passed onto offspring
So it’s incorrect
Wallace’s theory
Same evolution by natural selection theory as Darwin
Came up with it separately at the same time
So they jointly published their studies
Speciation
How new species form from different animals
What did Wallace notice when studying speciation?
Closely related species are separated by geographical barriers eg a river
How do new species form?
If a geographical barrier separates a population
The population could once interbreed and spread mutations
But now they can’t breed
And natural selection favours different alleles on either side that will change the population
Thus 2 they can’t spread this mutation and will develop into separate species
How do we know when we have developed a different Species?
Can no longer interbreed to produce a fertile offspring
Who came up with many of the discoveries of genetics?
Gregor Mendel
How did Mendel carry out experiments?
Looked at shape of the pea pods and its flowers
What did Mendel’s experiments show him?
Genes aren’t blended together but we get how we look from inherited units
These don’t change as we pass them down
These could be masked and reappear with later generations
How was mendel’s work accepted?
Scientists studied cell division and saw chromosomes act in a similar way to what Mendel said
What organisms evolves extremely quickly?
Bacteria under ideal conditions
Examples of antibacterial resistant
MRSA
What causes bacteria resistance to antibiotics?
Mutation causes one to be resistance to antibiotics
Antibiotic kills all bacteria except the resistant one
So it begins to reproduce with no competition = resistant strain rises and spreads
How to reduce bacteria resistance?
Not prescribe antibiotics inappropriately
Patients complete course of antibiotics so none can mutate
Restrict use in farming
Problem with creating new antibiotics
Too slow and expensive
Once developed it can’t keep with the new strains of resistant bacteria
