Inheritance, Variation and Evolution Flashcards
How is genetic variation created?
through mutations
What is a mutation?
change in the DNA code
What is natural selection?
fittest individual due to mutation is more likely to survive and reproduce
Which two factors contribute to the variation between organisms?
mutations and natural selection
What is speciation?
the process in which a species evolves to become another species
What was Lamarck’s theory?
an organism could acquire new traits during their lifetime, and these traits would be passed onto their offspring
What was Darwin and Wallace’s theory?
the variation in species means that the more favourable traits allow the organisms to survive and reproduce more, spreading throughout the population
What were 3 reasons people didn’t accept Darwin and Wallace’s theory?
religious reasons, lack of evidence, DNA hadn’t been discovered yet`
According to Darwin and Wallace’s theory, why do giraffes have long necks?
Giraffes with longer necks were better adapted to their environment
According to Lamarck’s theory, why do giraffes have long necks?
Giraffes acquired longer necks during their lifetime and passed this trait to their offspring.
What is selective breeding?
taking the best plants or animals and breeding them together in hopes to get a better offspring
What is a drawback of selective breeding?
reduces the gene pool of the population
What type of variation can be passed on to the next generation?
Genetic variation
What effect does selective breeding usually have on variation within a population?
It decreases variation
What is the term used to describe all the genes and their alleles found in a population?
genepool
What is the term used to describe the breeding together of closely related individuals?
inbreeding
What is genetic engineering?
modifying an organism by changing their genome for a benefit
What is gene therapy?
giving a person a healthy version of the gene that is causing the illness
What is one reason gene therapy is very difficult?
the faulty gene is in every cell of the body so we would have to transfer the healthy gene into every cell in the body.
How do you trasfer a gene from one organism to another?
1) you isolate the gene you want from the organism
2) you put it in a vector (virus of bacterial plasmid)
3) you make the other organism take up the vector and with it the gene.
What is the Human Genome Project (HGP)?
a major international research effort aimed to map out the entire human genetic code
How many genes has the HGP identified?
around 20,500 human genes
How many human genes have been found to be linked to diseases?
2,000
How do you clone an organism?
1)take an egg cell of the donor female and remove its nucleus
2) take an adult body cell and remove its nucleus
3)Put the body cell nucleus into the egg cell
4)Stimulate the cell to start dividing and forming an embryo.
5)Implant the embryo into a surrogate mother and wait for it to be born like normal.
What do you call a cell with its nucleus taken out?
enucleated cell
what is a clone?
an individual which is genetically identical to another individual
What is a transgenic organism?
an organism with DNA from another organism
How do you clone an embryo?
1) Pick the two organisms (of the same species) that have the most desirable traits
2)take sperm and use it to fertilise the egg.
3) let the zygote develop into an embryo
4) Separate the embryo into smaller embryos
5) Implant each embryo into a surrogate mother and the offspring will all be clones`
How do you clone a plant through cuttings?
1) find a plant you want to clone
2) Cut off a small part (ideally a growing shoot or branch)
3) Place the cutting in soil with nutrients
4) the cutting will grow into a clone of the original plant
What is another way to clone plants other than cuttings?
micropropagation
How does micropropagation work?
1) find a plant you want to clone
2) take a small piece of plant tissue from the tips of the stems
3) sterilise it to remove microorganisms
4) Place the explants in a nutrient medium (agar) and let them grow into small masses of cells called calluses. The nutrient medium should also contain growth hormones.
5) Transfer the calluses to soil where they can grow into plantlets (basically baby plants).
6) The plantlets can then be transferred to their own pots to develop into genetically identical adult plants.
What are explants?
very small pieces of plant tissue from the tips of stems
What are calluses?
small masses of cells grown from explants
What are plantlets?
small baby plants
Give two benefits of cloning via cuttings rather than micropropagation.
Cuttings is quicker
Cuttings is cheaper
Cuttings requires less technical expertise/equipment
Don’t have to worry about sterilisation so much for cuttings
What are 3 types of fossils?
skeletons made of rock
impressions in the ground
organisms that havent decayed yet
Why do we study fossils?
to see how organisms have changed over millennia and give proof for evolution
What are the 3 main ways fossils form?
gradual replacement by minerals
casts and impressions
preservation
How do fossils form by gradual replacement by minerals?
body parts like bones teeth and shells decay slowly so as they decay they can be replaced by minerals to form rock like substances in the exact same shape and size as original structures.
How are casts made?
when an organism is buried in a soft material (e.g clay) and it hardens whilst the organism decay.
HOw are impressions made?
often footprints or marks in the ground around which the material has hardened
Why is it difficult to find out how life first began on the earth through fossils?
early life forms were soft bodied so decayed too quickly.
Fossils formed so long ago may have been destroyed
When can we say a species has gone extinct?
no individuals of that species remain
What is the most common reason a species goes extinct?
sudden environmental change
What are 3 reasons for extinctions?
rapid environmental change
new predator kills all
new species out competes them
new disease kills all
catastrophic event kills all
Who was Wallace?
a scientist who presented the theory of evolution by natural selection along with Darwin.
What 2 things is Wallace best known for?`
1) studying warning colouration in animals
2) his theory of speciation
What is speciation?
the formation of a new species
What is isolation?
A physical barrier (river, mountains etc.) which separates the population
How does isolation cause speciation?
The populations live in different environments, so different traits are more favourable making the populations’ evolution different and eventually creating a new population
What is antibiotic resistance?
when bacteria develop to be able to survive antibiotics
Give 3 reasons antibiotic resistance is becoming more common.
antibiotics are being overused
many people dont take the full course
huge amounts of antibiotics are given to farm animals
What did Linnaeus do?
in the 1700s, he classified animals by their characteristics and bone structures
What is the order of the Linnean system?
kingdom, phylum, class, order, family, genus, species.
What is the binomial naming system?
a way to identify an organisms using their genus and species.
What did Woese introduce?
the 3 domain system
What are the 3 domains?
bacteria, eukaryota, archaea
Where do the domains fit in in the Linnean system?
above kindoms
What are 2 advantages of the binomial naming system?
each species has a unique name
it lets scientists discuss individual species
What 4 types of organisms are considered eukaryotes?
fungi, plants, animals, Protoctista
What are the 3 steps of protein synthesis?
transcription and translation?
What is transcription?
the process of taking a single gene and turning it into an mRNA strand
What is translation?
the process of taking an mRNA strand and using it to produce a protein
Where does protein synthesis take place?
ribosome
What are the differences between mRNA and DNA?
much shorter than DNA
mRNA is only a single strand
mRNA contains U instead of T
mRNA is complementary to DNA
What is a codon?
3 bases which code for a specific amino acid
What does the tRNA do?
brings amino acids to the ribosomes so they can make the protein. They also have an anti- codon
What is the purpose of the anti-codon on the tRNA?
to ensure that it binds to the right codon and therefore gives the right amino acid
Where does transcription take place?
nucleus
Why does a gene of DNA have to be copied to mRNA (transcription)?
DNA is too large to leave the nucleus
What happens when the ribosome finishes making an amino acid chain?
it detaches itself from the ribosome then folds up to become a protein
What is a chain of amino acids called?
polypeptide
