natural selection and genetic modification Flashcards
describe the process of natural selection (6)
1) differences in alleles/new alleles arise through genetic mutations resulting in genetic variation in a population
2) selection pressures such as predation, competition for resources and disease can affect an organism’s chance of surviving and then reproducing
3) individuals with characteristics that make them better adapted and therefore more likely to survive and reproduce
4) the useful alleles are more likely to be passed on to the next generation
5) worse adapted individuals are less likely to survive so the less desirable traits gradually disappear
6) beneficial characteristics become more common in the population
what are examples of evidence for evolution
fossils
bacteria
fossil
any trace of an animal or plant that lived a long time ago, mostly found in rocks
how are fossils used as evidence for evolution
by observing fossils chronologically, we can observe gradual changes in organisms
this shows evolution as it shows how species have changed and developed over billions of years
how are bacteria used as evidence for evolution
bacteria sometimes develop genetic mutations, forming new alleles which can change its characertistics, for example it develops antibiotic resistance
bacterium that are resistant are more likely to survive for longer so it can reproduce more
resistance is therefore passed on to lots of offspring and the allele spreads to become more common in the population
this shows evolution as it makes bacteria better adapted to an environment in which antibiotics are a selection pressure
who published papers on evolution
Darwin and Wallace
what did Darwin observe
that there was variation within the same species
those best suited to the environment were more likely to survive
these traits could be passed onto offspring
what are 3 areas in modern biology that have been impacted by idea of evolution
classification
antibiotic resistance
conservation
how has classification been impacted by idea of evolution
we now classify organisms based on how closely related they are
how has antibiotic resistance been impacted by idea of evolution
we understand the importance of finishing a course of drugs to stop resistant bacteria from spreading
we know the need to constantly develop new antibiotics
how has conservation been impacted by idea of evolution
we recognise the importance of genetic diversity and how it helps populations to adapt to changing environments
this has led to conservation projects to protect species
hominids
human beings and their ancestors
what are 3 examples of hominid fossils
Ardi (ardipithecus ramidus)
Lucy (australopithecus aferensis)
Richard Leakey’s hominid fossils including Turkana boy (homo erectus)
how old was ardipithecus ramidus (Ardi)
4.4 million years ago
features of ardipithecus ramidus (Ardi) (4)
- ape-like big toe for gripping branches when climbing trees
- long arms and short legs (apelike)
- brain size the same as a chimpanzee’s
- leg structure suggests walking upright
how old was australopithecus aferensis (Lucy)
3.2 million years ago
features of australopithecus aferensis (Lucy) (4)
- arched feet for walking rather than climbing, no ape-like big toe
- arm and leg length between human and ape
- larger brain than Ardi but still chimp size
- leg structure suggests walking upright more efficiently than Ardi
how old was Leakey’s Turkana boy (homo erectus)
1.6 millions years ago
features of homo erectus (Turkana boy) (4)
- more human like than Lucy
- short arms, long legs ; more human like
- much larger brain, similar to human size
- even better adapted to walking upright than Lucy
what are two examples of evidence for human evolution
hominid fossils
use of stone tools
the homo species developed , what are the 4 species
homo habilis
homo erectus
homo neanderthalensis
homo sapiens
how old was homo habilis and how did he use stone tools
2.5-1.5 million years ago
simple stone ‘pebble tool’s made by hitting rocks together to make sharp flakes which could be used to scrape meat from bones or crack bones open
how old was homo erectus and how did he use stone tools
2-0.3 million years ago
rocks sculpted to produce more complex tools like hand axes
could be used to hunt, dig, chop, scrape meat from bones
how old was homo neanderthalensis and how did he use stone tools
300 000 - 250 000 years ago
more complex tools - evidence of flint tools, pointed tools and wooden spears
how old was homo sapiens and how did he use stone tools
200 000 years ago - now
widely used flint tools - pointed tools such as arrowheads, fish hooks and needles
how can we date stone tools (3)
structural features - simpler tools are more likely to be older
stratigraphy - older rock layers are usually found below younger rock layers ; the lower the layer of rock, the older the tool
carbon-14 dating - some stone tools contain carbon which can be dated
pentadactyl limb as evidence for evolution?
the limb with 5 digits is present in many species, all with a similar bone structure but generally a different function
similarity in bone structure suggests that all species with a pentadactyl limb are evolved from a common ancestor
what was the old classification system
organisms were organised by observable similarities and differences
living things were organised into the 5 kingdom system
each kingdom was divided up into smaller groups
what were the 5 kingdoms
animals, plants, fungi, prokaryotes, eukaryotes
what was each kingdom divided into
phylum -> class -> order -> family -> genus -> species
why was the classification system rethought such that it is now the 3 domain system
technology has developed further so we can understand biochemical processes and genetics better
- we can sequence an organism’s genome and compare it with other genomes (the more similar they are, the more closely related they are) - this can be done with RNA sequences
what did Woese suggest about the classification system
WOESE suggested that organisms be reclassified as members of the prokaryote kingdom weren’t as closely related
he said that before kingdoms, we should have domains
what are the 3 domains
archaea
bacteria
eukarya
archaea domain
organisms in this domain look similar to bacteria but are different in terms of DNA and RNA sequences
found in extreme places (extremophiles)
bacteria domain
contains TRUE bacteria
eukarya domain
a broad range of organisms (fungi, plants, animals, protists)
selective breeding (definition)
when humans artificially select the plants and animals that are going to breed so that the desirable characteristics remain in the population
selective breeding process (4)
1) from your existing stock, select ones with the desired characteristic
2) breed them with each other
3) select the best offspring and breed them together
4) continue this process over several generations as the trait becomes stronger until all offspring have the characteristic
what are 2 advantages of selective breeding
+ in agriculture, genetic variation means that some cattle produce more meat which will lead to a greater meat yield
+ in medical research, rats have been bred with a strong or weak alcohol preferences to allow us to understand brains and behaviour better
what are 3 disadvantages of selective breeding
- reduces the gene pool because same animals are used
- inbreeding can cause health problems as there is a greater chance of organisms inheriting harmful genetic defects
- serious problems if a new disease appears as there is little genetic variation so the population is not likely to be resistant
tissue culture
growing cells on an artificial growth medium
how do plants use tissue culture
whole plants can be grown using tissue culture very quickly and all year round
plants produced via tissue culture are clones so you can make organisms with the same beneficial features
tissue culture of plants (process) (4)
1) choose a plant with desirable traits which you want to clone
2) remove several piece of tissue from parent plant ( best results when taken from roots or shoot)
3) grow tissue in a growth medium that contains all nutrients and growth hormones required - do under ASEPTIC conditions
4) as the tissues produce shoots and roots, transfer to potting compost to grow
how do animals use tissue culture
often used in medical research as you can carry out experiments on tissues in isolation, observing effects of environmental changes or substances on cells without impacting an entire organism
you CANNOT grow whole animals using tissue culture
tissue culture in animals (process) (5)
1) sample of tissue extracted
2) cells are separated using enzymes
3) placed in a culture vessel and bathed in growth medium which encourages growth and multiplication
4) after many rounds of cell division, cells can be split once more using enzymes to grow further
5) once grown, tissue can be stored for future use
genetic engineering
modifying an organism’s genome to introduce desirable characteristics
4 uses of genetic engineering
agriculture - crops can be modified to be resistant to herbicide ( farmers can then kill weeds without damaging the crop ; increasing crop yield )
medicine - bacteria can be engineered to produce insulin
animals - genes with useful proteins can be transferred from animals to livestock where they are produced and then extracts (eg. antibodies for therapy)
organ transplantation - animals with suitable organs could be produced for humans
what are 3 risks of genetic engineering
- genetically modified crops could have adverse effects on food chains or human health
- transplanted genes may get out into the environment creating other organisms such as ‘super weeds’
- hard to predict the effect of modification on an organism
vector
something used to transfer DNA into a cell
how would you insert DNA into another organism (process) (5)
1) dna you want to insert is cut out with restriction enzymes - the vector is also cut with the same enzyme
2) vector DNA and inserting DNA are left with sticky ends which are joined toegether using ligase enzymes
3) the two DNA pieces make recombinant DNA
4) the recombinant DNA is inserted into other cells
5) cells can now produce the desired protein (for example human insulin production)
GMOs / GM organisms
genetically modified organisms
how are GMOs being usd to provide foood
as the world population grows, global food production also has to grow
the food used for this needs to have the right balance of nutrition
GM crops can increase food production as they can be bred to be resistant to pests, droughts etc.
some crops are modified to treat/combat deficiency disease
what was golden rice
golden rice is a GMO that was engineered to produce a chemical which, once in the body, produces vitamin A
explain the use of bacillus thuringiensis (Bt) in insect resistance in crops
the bacillus thuringiensis (Bt) is a bacterium that produces a toxin capable of killing many harmful insect larvae
the gene for the Bt toxin is inserted into crops so they prodce the toxin in their steams and leaves so that they are pest resistant
the toxin is pecific to insect pests
the long term effects of Bt exposure are not yet known or understood
why do farmers still have to use insecticides alongside gmo crops containing the Bt toxin gene
insects that feed on the crops are constantly exposed to the toxin so there is a danger of developing resistance
using other insecticides helps to prevent this
