Inheritance, variation and evolution

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  • Created by: leo1223
  • Created on: 31-05-18 12:26
What distinguishes asexual reproduction from sexual reproduction?
Asexual reproduction requires only one parent, no fusion of gametes, so not mixing of genetic information, produces genetically identical offspring (clones), involves mitosis
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Explain a variety of ways that plants use to asexually reproduce?
Strawberry plants send out long shoots (runners), which touch the ground grow a new plant, daffodils produce small bulbs, which grow into new plants, fungi reproduce asexually by spores, malarial protists reproduce asexually when inside a human host
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What the names of the gametes in animals?
Sperm and egg cells in animals
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What are the names of the gametes in flowering plants?
Pollen and egg cells in flowering plants
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What is sexual reproduction?
Sexual reproduction is the fusion of male and female gametes
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What distinguishes sexual reproduction from asexual reproduction?
Sexual reproduction requires two parents, sexual reproduction leads to the mix of genetic information, which produces variation in the offspring, the formation of gametes involves meiosis
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Describe the process of meiosis?
Each chromosome in a diploid cell replicates itself, chromosomes are pulled to opposite poles, cell divides for the first time, copies now separate and second cell division takes place, 4 gametes are formed
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What are the differences between meiosis and mitosis?
Meiosis forms 4 daughter cells from one parent cell that are all genetically different, where as mitosis forms 2 daughter cells from one parent cell, both daughter cells are identical copies
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What are the advantages of sexual reproduction?
It produces variation in the offspring, if the environment changes any variation means that some organisms will be suited to the conditions and survive, it allows humans to selectively breed animals and plants, which increases food production
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What are the advantages of asexual reproduction?
Only one parent is needed, it is more time and energy efficient, as the organism does not need to find a mate, it is faster than sexual reproduction, many identical offspring can be produced at one time, which increases chances of survival of species
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Explain how some plants are able to reproduce asexually and sexually?
Many plants can produce seeds by sexual production and can also reproduce asexually e.g. by using bulbs and runners
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Explain how some fungi are able to reproduce asexually and sexually?
Many fungi can make spores by asexual or by sexual reproduction
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Explain how malaria protists are able to reproduce asexually and sexually?
Malaria protists reproduce sexually in the mosquito as well as asexually in humans
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What is the function of a gene?
A gene codes for a particular sequence of amino acids, to make a specific protein
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What is the genome?
The genome is the entire genetic material of a organism
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What are scientists able to do now that they have studied the human genome?
Scientists are able to search for genes linked to different types of disorders, helps scientists understand the cause of inherited disorders and how to treat them, scientists can now investigate how humans may have changed over time
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What is DNA and what is it made up of?
DNA is a polymer made up of repeating units called nucleotides, each nucleotide consists of a sugar, a phosphate and one of the four bases, each molecule has two alternating sugar and phosphate stands, attached to each sugar is one of the four bases
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What holds the two strands together?
It is an attraction between different bases that holds the two stands together, C is always linked to G on opposite strand, T is always linked to A on opposite strand
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What does the order of the bases on DNA control?
The order of bases on DNA controls the order in which amino acids are joined together to make a particular protein
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What codes for one amino acids?
A sequence of three bases codes for one amino acid
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How are proteins synthesised?
Proteins are synthesised on ribosomes using a template that has been taken from the DNA and carried out of the nucleus, carrier molecules then bring specific amino acids to add to the growing protein chain
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What happens when the newly synthesised proteins are finished?
When the protein chain is finished, it folds up to form a unique shape, the unique shape allows the proteins to do their job as enzymes, hormones or structural proteins such as collagen
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What two external factors can increase the rate at which mutations occur?
Certain chemicals and high-energy radiation can increase the rate at which mutations occur
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What is mutation?
A mutation is any change that occurs in the DNA's structure
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What is the effect of a mutation affecting any of the bases?
If any bases in the DNA are changed by a mutation, then it may change the order of amino acids in the protein coded for by the gene. Which may cause a different protein to be synthesised instead
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Why are mutations not extremely deadly?
Mutations occur all the time, most do not alter the protein, or only alter it slightly, so that it still works
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What is the effect of a mutation affecting the shape of a protein?
If the protein that has been altered is an enzyme, then the substrate may no longer fit into the active site, if it is a structural protein, the change in shape may cause it to lose its strength
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What are "non-coding" parts of DNA
Non-coding parts of DNA are parts of DNA that do not code for proteins instead they can switch genes on/off so that they can/cannot make specific proteins
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What is the effect of a mutation affecting a non-coding section of DNA?
If a mutation affects a area of non-coding DNA, it may affect how genes are expressed
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How can mutations cause evolution?
Occasionally, a mutation may occur that is useful. Without this type of variation, evolution by natural selection would not occur
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How are most characteristics controlled?
Most characteristics are controlled by several genes working together
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What is it called if only one gene controls one characteristic?
Monohybrid inheritance
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What is meant by a "allele"?
Each gene may have different forms called alleles
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What two disorders are inherited?
Polydactyl (having extra toes or fingers) caused by a dominant allele, Cystic fibrosis (a disorder of cell membranes) is caused by a recessive allele
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What are sex chromosomes?
Sex chromosomes are the pair of chromosomes that determine sex
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What was commonly believed about sexual reproduction up until the mid 19th century?
Many people though sexual reproduction a blend of characteristics
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How did Gregor investigate the common beliefs about sexual reproduction in the mid 19th century?
Gregor Mendel investigated the common beliefs by carrying out breeding experiments on pea plants
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What did Gregor Mendel discover from his experiments?
Gregor Mendel discovered that characteristics are determined by 'units' that are inherited and do not blend together
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Why was the importance of Gregor Mendel's discovery not recognised during his lifetime?
He was a monk working in a monastery, not a scientist at a university, he did not publish his work in a well known book or journal
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What did scientists observe in the late 19th century about Mendel's units and genes?
In the late 19th century, after Gregor Mendel's discovery scientists observed the behaviour of chromosomes during cell division
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What did scientists conclude in the early 20th century about chormosomes?
In the early 20th century, scientists realised that chromosomes and Mendel's 'units' behaved in similar ways. They decieded that Mendel's 'units' renamed genes, were located in the chromosomes
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What did scientists in the mid 20th century discover about DNA?
In the mid 20th century, scientists worked out what the structure of DNA looked like and the mechanism by which genes work
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How many alleles does an individual receive from each of their parents?
An individual always receives two alleles for each gene, one allele from the mother, one allele from the father
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What is meant by the term 'phenotype'?
How the alleles are expressed (what characteristic appears) is called the phenotype
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What is meant by the term 'genotype'?
The combination of alleles present in a gene is know as the genotype
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What is meant by 'homozygous'?
If the two alleles present are the same e.g. BB or bb, the person is homozygous
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What is meant by 'heterozygous'?
If the two alleles present are different e.g. Bb or bB, the person is heterozygous
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What is meant by variation?
Variation is the differences in the characteristics of individuals in a population
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What differences in inviduals cause variation?
The genes that individuals have inherited, the conditions in which individuals have developed (environment), a combination of both genetic and environmental causes
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How does sexual reproduction causes variation?
Sexual reproduction produces different combinations of alleles and therefore causes variation
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How do mutations causes variation?
Mutations create new alleles and therefore cause variation
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What is meant by the term "evolution"?
Evolution is the gradual change in the inherited characteristics of a population over time
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What can cause a new species to form?
Evolution can cause the formation of a new species
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What is meant by "natural selection"?
Natural selection is the theory put forward by Darwin to explain how evolution occurs
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Describe Dawin's theory of natural selection?
Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring.
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What were the four important observations Darwin made during his his round the world expedition?
Darwin observed that organisms often produce large numbers of offspring, populations usually stay about the same size, organisms are all slightly different-they show variation, characteristics are inherited
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What were the five conclusions Darwin made from his observations?
there is a struggle for existence, more organisms are born than can survive, the ones that breed are best suited to the environment, pass on their characteristics to their offspring, over long periods of time the characteristics of populations change
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What are the reasons as to why Darwins theory took the public and scientists a long time to accept?
Darwins theory challenged the idea that God made all the organisms, there was not enough evidence at the time to convince the scientists, the mechanism of inheritance and variation was not known until 50 years after the theory was published
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What was Lamarck's theory?
Lamarck's theory was based on the idea that changes that occur in an organism during its lifetime can be inherited
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What was one problem with Darwin's theory that has now been solved?
the mechanism of inheritance and variation are now known
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What is the other evidence for evolution?
Fossils provide evidence for evolution
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What are fossils?
Fossils are the remains of organisms from hundreds of thousands of years ago that are found in rocks
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What are the four different ways that fossils can be formed?
From the hard parts of animals that do not decay easily, from parts of organisms that have not decayed because one or more conditions needed for decay was absent, when parts of the organisms are replaced, as preserved traces of organisms
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What do scientists use fossils for?
Scientists use fossils to look at how organisms have gradually changed over long periods of time
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Why are there gaps in the fossil records?
There are gaps in the fossil records because many early forms of life were soft-bodied, which means that they have left very few traces behind, remaining traces may have been destroyed by geological activity
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How can the development of antibiotic-resistant strains of bacteria be used to explain the theory of natural selection?
Bacteria can evolve rapidly because they reproduce at a fast rate, when they reproduce, mutations occur, some mutated bacteria can become resistant to antibiotics and are not killed, these bacteria survive and reproduce so a resistant strain develops
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What do humans use selective breeding or artificial selection for?
Humans use selective breeding or artificial selection for thousands of years to produce: food crops from wild plants and domesticated animals from wild animals
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What is selective breeding?
Selective breeding is the process by which humans breed plants and animals with particular, desirable genetic characteristics
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Describe the process of selective breeding?
Choose parents that best show the desired characteristic, breed them together, from the offspring, again choose those with the desired characteristics and breed, continue over many generations
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What is the one disadvantage of selective breeding?
Selective breeding can lead to 'inbreeding' where some breeds are particularly prone to disease or inherited defects
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What is genetic engineering?
Genetic engineering the deliberate modification of the characteristics of an organism by manipulating it's genetic material
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Where does protein synthesis occur?
In the ribosomes
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Describe how genetic engineering is done?
Enzymes are used to isolate the required gene, this gene is inserted into a vector e.g. bacterial plasmid or virus, the vector is used to insert the gene into the required cells
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What happens if genes are inserted into an organism's cells during the embryo cell stage?
If the genes are put into the cells of animals or plants at the egg or embryo stage, then all cells in the organism will get the new gene
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What are GM crops?
GM crops are plants that have had their genes genetically modified
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What have crops been genetically modified to be?
Crops have been genetically modified to be resistant to diseases, insects or herbicide attacks, to produce bigger, larger fruits
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Why are some people concerned about GM crops?
Some people are concerned about GM crops and the possible long-term effects on populations of wild flowers and insects and on human health (if consumed)
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What have fungi and bacteria been genetically modified to do?
Fungi and bacterial cells have been genetically engineered to produce useful substances e.g. human insulin to treat type 1 diabetes
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What may be possible in the future due to genetic engineering?
In the future, it may be possible to use genetic modification to cure or prevent some inherited diseases in humans
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What are clones?
Clones are genetically identical individuals
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How are clones produced naturally?
Clones are produced naturally by asexual production
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What can produce identical plant clones?
Cuttings, tissue cultures
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Describe what is meant by a tissue culture?
A tissue culture is where small groups of cells are used to grow new plants, this is used commercially and to preserve rare species of plant
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How can animals be cloned?
In animals, clones can be produced by splitting apart cells from an embryo before they become specialised, then transplanting the identical embryos into host mothers
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Describe how adult cells are able to be used to clone animals?
Remove the nucleus from unfertilised egg, insert nucleus from a adult body cell (which is cloned) into empty egg cell, stimulate the egg to divide using a electric shock, allow embryo to develop into more cells, insert embryo into womb of female
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What are the 7 categories of Carl Linnaeus' classification system?
Kingdom->Phylum->Class->Order->Family-> Genus->Species
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How are organisms named?
Organisms are named by the binomial system i.e the first part of their name is their genus, the second part is their species
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Why were new models of classification proposed by scientists?
Microscopes improved, so scientists learnt more about cells, biochemical processes became better understood
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Who developed the three-domain system?
Carl Woese
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How are organisms classified in Carl Woese's system?
In this system organisms are divided into: archaea, bacteria, eukaryota
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How can extinction be caused?
Extinction may be caused by: changes to the environment over long periods of time, new predators, new diseases, new, more successful competitors and a single catastrophic even e.g. volcanic erruption
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What are members of the same species able to do and why?
Members of the same species are similar enough to be able to breed with each and produce fertile offspring
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Who proposed the theory of speciation?
The theory of speciation was proposed by Alfred Russel Wallace
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Explain the theory of speciation?
Populations become physically isolated from each other, genetic variation is present in both two populations, natural selection operates differently in both populations, the populations become so different that successful interbreeding is impossible
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Card 2

Front

Explain a variety of ways that plants use to asexually reproduce?

Back

Strawberry plants send out long shoots (runners), which touch the ground grow a new plant, daffodils produce small bulbs, which grow into new plants, fungi reproduce asexually by spores, malarial protists reproduce asexually when inside a human host

Card 3

Front

What the names of the gametes in animals?

Back

Preview of the front of card 3

Card 4

Front

What are the names of the gametes in flowering plants?

Back

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Card 5

Front

What is sexual reproduction?

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