Topic 4 - Natural Selection and GM Flashcards
theory of evolution
- all species of living things today descended from the first simple life forms
- new species arose from existing ones whilst others became extinct
what is evolution?
the slow and continuous change of organisms’ inherited characteristics from one generation to next
natural selection ( part 1 )
- individuals in same species population show genetic variation
- due to random mutation in DNA producing different alleles
natural selection ( part 2 )
- selection pressures ( such as predation , disease ) affects an organism’s chance of surviving
natural selection ( part 3 )
- those better adapted to the s.p have a better chance of survival and more likely to reproduce
- alleles responsible for useful characteristic more likely to be passed down to next gen
natural selection ( part 4 )
- less well adapted individuals less able to compete and therefore less likely to reproduce and survive
- over time, they will decrease in number and eventually become extinct
- beneficial characteristics become more common in the population over time
what is a fossil?
a trace of an animal or plant that lived millions of years ago and found in rocks
how can fossils be dated?
- statigraphy : oldest fossils found in lower rock layers
- radiometric dating
how do fossils prove evolution?
- by arranging fossils in chronological order
- gradual changes can be observed, showing development
who were the two scientists that were involved in theory of evolution?
- charles darwin
- alfred russel wallace
who did humans evolve from?
humans and chimpanzees evolved from a common ancestor - a species of ape
Ardi
- fossil from 4.4 mill years ago
- opposable big toe to grasp branches - suggests she climbed trees
- long arms and short legs
- brain size same as chimp
- structure of legs suggests she walked upright
Lucy
- fossil from 3.2 mill years ago
- arched feet more adapted to walking, no opposable big toe
- size of arms and legs in between chimp and human
- brain were slightly larger than Ardi
- structure of Lucy’s leg bone suggest she walked upright more efficiently
Leakey’s fossil : Turkana Boy
- fossil from 1.6 mill years ago
- short arms and long legs are much more like a human
- brain size similar to human
- structure of legs suggests he was even better adapted to walking upright
how do these fossils prove evolution
- the more recent fossils are more similar to humans
- longer legs, shorter arms
- larger brain size
- better adapted to walking
how are stone tools evidence for human evolution
- the more recent tools are more complex
- shows the human brain was getting larger, showing evolution
how does pentadactyl limb prove evolution?
they are limbs with five digits
you see it in all organisms with 4 limbs
- in diff groups of animals, they have similiar bone structure but diff function
- similar bone structure provides evidence of common ancestor
what are the five kingdoms
- animals
- plants
- fungi
- protists
- prokaryotes
classification method divisions
( Kids Prefer Cake Over Free Green Salads )
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
how has our understanding of biochemical processes and genetics increased?
- scientists able to determine sequence of DNA bases in diff organisms’ genes
- compare them. more similar : closely related
how did genetic analysis led to the suggestion of 3 domain classification
- using RNA sequencing
- Woese found out that some members of prokaryote kingdom weren’t as closely related as thought
- archaea domain are quite different to bacteria domain as their DNA & RNA sequencing shows
what is selective breeding?
it is when humans artificially select the plants and animals to breed so the genes for particular characteristics remain in population
difference between selective breeding and natural selection
- selection pressure causes better adapted species to reproduce in natural selection
- humans choose which animals to reproduce in selective breeding
how does selective breeding work?
- from existing stock, humans select which have desired characteristics
- breed them with each other
- select best of offspring and breed them together, continue process over next several generations
uses of selective breeding
- improve crop yields
- more meat from cows and pigs
- more milk from cows
problem with selective breeding
reduces the gene pool
why is reducing gene pool harmful?
- more chance of inheriting harmful genetic defects
- if a new disease appears, there is not much variation so it if it kills one, others are likely to succumb
what is tissue culture
when cells are grown in an artificial growth medium
plant tissue culture use
- grow plants from the cells of a single individual
- plants produced are clones and are genetically identicaql
process of plant tissue culture ( p1)
- choose the plant to clone, with beneficial characteristics
- remove small pieces of tissue from plant stems, called explants
-placed in artificial growth medium ( agar jelly ) that contains growth medium and nutrients to help tissue grow into plants
process of plant tissue culture ( p2 )
- done under aseptic conditions to prevent growth of microbes that could harm plants
- when the plants have grown roots they are moved to glasshouse and placed in pot containing compost
- light intensity, temp controlled
advantages of plant tissue culture
- plants can be grown quickly
- all year round
- in very little space
- all plants will have desired characteristic
what is genetic engineering?
- a gene is transferred from one organism’s genome to another organism’s genome
- in order to introduce desirable trait
uses of genetic engineering
- improve size and quality of fruit
- cows produce useful human proteins in milk
- bacteria producing human insulin
process of genetic engineering (p1)
- plasmid vector physically removed from bacterium
- restriction enzyme used to cut open plasmid DNA to produce uneven sticky ends
- same restriction enzyme used to cut out desired gene
- vector DNA and gene with complimentary sticky ends
process of genetic engineering (p2)
- dna ligase enzyme joins complimentary sticky ends together
- makes recombinant dna
- recombinant dna is inserted into bacteria which is now a gmo
- can divide millions of times and all produce protein we want
benefits of genetic engineering
- has a more immediate effect than selective breeding
- as DNA carries a universal code, genes can be transferred from ANY species
concerns about genetic engineering
- hard to predict what effect changing the genome will have on organism
- transplanted genes may get out into environment
- herbicide resistant gene can be picked up by weeds - superweed
benefits of GM crops
- increase the amount of food a crop provides : its yield
- Gm crops can be engineered to contain additional nutrients
concerns about gm crops
- concerns about long term effects of gm crops on human health
- countries may be too dependent on gm seeds
benefits of bt crops
- improves crop yields as insects are killed off
- reduces need for chemical pesticides
risks of bt crops
- insects constantly exposed to toxin so could develop resistance
other methods of increasing food production
- fertilisers
- biological control
