SB4: natural selection & genetic modification Flashcards
who made the theory of evolution?
darwin & wallace
what was darwin’s theory?
(survival of the fittest/natural selection)
-individuals with characteristics most suited to the environment are more likely to survive and to breed successfully
-the characteristics that have enabled the to survive are then passed on to the next environment
what is natural selection?
the species that is more adapted to surviving in its environment will survive the longest and pass on it’s genes
steps of natural selection
- an individual of a species shows genetic variation
- there is a random environmental change and competition happens
- better adapted individuals survive
- survivors pass on their better genes, generations later there will only have the genetics of the original suvivors
what are antibiotics?
chemicals produced by bacteria and fungi that inhibit or kill other microbes
natural selection shown through antibiotics
- random mutation happens in bacteria, nothing happens until antibiotics are used
- antibiotics are introduced and the mutated bacteria becomes resistant
- while the other bacteria dies, a point is reached where only resistant bacteria remains and they reproduce, all the population consists of the resistant bacteria
- the immune system is left to deal with these bacteria as they can’t be killed through antibiotics
evolution
the gradual change in a species over time so that they can become more suited to an environment
humans
homo sapiens
what is a fossil?
the preserved remains of a dead organism from millions of years ago
when do fossils form?
-when hard body parts, such as bones and shells, which do not decay easily or are replaced by minerals as they decay
-when parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
-preserved traces of organisms become covered by layers of sediment, which eventually become rock
what is the problem with fossils?
-few organisms form fossils
-there are gaps in fossil records
-there may be minimal DNA
-fossils may get damaged
how can you tell the time that tools were from?
carbon dating
pentdactyl limb
similar structure suggests that many vertebrates descended from the same common ancestor
ancestors of humans…
hominins
ardi (ardipithecus ramidus)
-4.4 million ears old
-skull = 350cm³
-big toes stuck out for climbing
australopithecus afarensis (lucy)
-4.3 million years ago
-skull size: 400cm³
-probably walked upright
-toes arranged like humans
homo habilis
-first to make stone tools
-2.5-1.5 million years ago
-leakey’s
-skull size: 500 - 600cm³
-walked upright, short, long arms
homo erectus
-2-0.5 million years ago
-leakeys’s
-850 cm³ = skull size
-1.79m, strong build
homo sapiens
195,500 years
-skull size: 1450cm³
-upright walking
classification
the process of grouping things based on their similarities
what does classification do?
-make things easier to study
-helps us understand how living things are related
-allows us to make sense of the living world
-gives us a sense of the living world
binomial system
identifying organisms by their genus and species names (eg: homo sapien)
linnean classification
kingdom
phylum
class
order
family
genus
species
kingdom
animals
(multicellular, nuclei, no cell walls)
plants
(multicellular, chloroplasts, nuclei, cellulose cell walls)
fungi
(multicellular, live in/ on dead, nuclei, chitin in cell walls)
prokaryotes
(unicellular, no nuclei, flexible cell walls)
protists
(unicellular, nuclei, some have cell walls)
breeds vs varieties
breeds = new animals
varieties = new plants
selective breeding (artificial selection)
when humans breed plants and animals for particular genetic characteristics
inbreeding
when plants or animals are bred within a small gene pool
what can inbreeding lead to?
inherited disease or defects
selective breeding steps
- decide which characteristics are important enough to select
- choose parents that show these characteristics
- choose the best offspring from parents to produce the next generation
- repeat the process until all offspring show desired characteristics
advantages of selective breeding
-animals can be made that can’t cause harm
-more food or better quality food
-higher yield of food
disadvantages of selective breeding
-reduced gene pool
-inbreeding
-rare diseases could be unknowingly selected as part of positive trait
-reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive
desired characteristics in plants:
-disease resistance in food crops
-wheat plants that produce lots of grain
-large or unusual flowers
desired characteristics in animals
-animals that produce lots of milk or meat
-chickens that lay large eggs
-domestic dogs that have a gentle nature
how can you show if two animals are from the same species?
-breed them and their offspring should be fertile
clones
genetically identical individuals
what’s the simplest way to clone a plant?
taking a cutting
steps of cutting cloning
- branch from the parent plant is cut off, its lower leaves are removed, and the stem is planted in damp compost
- plant hormones are often used to encourage new roots to develop
- the cutting is usually covered in a clear plastic bag to keep it moist and warm
- after a few weeks, new roots develop and a new plant grow
what is tissue culture?
-the growing of cells or tissues in liquid containing nutrients/ on a solid medium (nutrient agar) to create identical cells
-they may form a callus (a clump of undifferentiated cells) and then get treated to make them differentiate and become specialised
why is everything in tissue culture sterilised?
to remove the pathogens so that the plants growth isn’t prohibited
how can tissue culture be used medically?
for transplants
what are the advantages of tissue culture?
-faster than vegetative reproduction
-can breed desirable traits
-not dependant of seasons
-extinct/endangered things can be brought back
disadvantages of tissue culture
-more labour and money used
-process not guaranteed success
genetic engineering
modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
vectors
carry and transmit disease
process of cloning animals
- 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
how is genetic engineering used?
- medicine (inherited disease
-agriculture (increasing yield)
-bacteria producing insulin
steps of genetic engineering/ modification
- restriction enzymes are used to isolate the required gene leaving it with sticky ends/unpaired bases
- a plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends
- the plasmid and the isolated gene are joined together by ligase enzyme.
the vector inserts the gene into required cells. - the genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics
yield
amount of something that is produced
bt toxin facts
-natural insecticide discovered in soil bacteria (1900)
-genes that produce this toxin were introduced to plants
-only affect insects that chew the plant tissues to pests that suck sap are left out and insecticides are still needed
-insects can develop resistance
-new versions of GM can be made to replace versions that pests are resistant to
GM crops advantages and disadvantages
advantages:
-more yield
-less presticides = less costs
-more profit
disadvantages:
-cost of production
advantages of pesticides
-very effective
-easy to apply
-can be used with almost all crops
-Used to get more profit
disadvantages of pesticides
-reduces biodiversity
-expensive
-increased pesticide resistance
-toxic
-may kill important & innocent animals
what are fertilisers?
chemicals added to soil to provide the nutrients needed for plant growth that was removed from ground after continuous plant growing
disadvantages of fertilisers
-eutrophication
-kill animals
biological control: advantages
-remove pests naturally
-non-toxic
-cheap
-long-term solution
-Usually highly specific to pest
biological control: disadvantages
-expensive to find
-takes long
-introduced non-indigenous species
-doesn’t remove 100% of species
