Inheritance Flashcards
1
Q
Meiosis and Mitosis leads to what type of cells being formed?
A
Meiosis - non-identical
Mitosis - identical
2
Q
Human cells contain how many chromosomes in their nucleus?
What about gametes
A
23 pairs.
Gametes have 23 individuals chromosomes in their nucleus - single and not paired.
Remember gametes are the reproductive cells of animals:
- MALES - Sperm
- FEMALES - Eggs
3
Q
What type of reproduction produces gametes?
A
Meiosis. (produces non-identical cells, so every sperm cell and every egg cell is different).
4
Q
What happens during mitosis?
A
1 cells is copied into two identical cells.
5
Q
2 examples of where meiosis occurs:
A
- In flowering plants, to produce the gametes egg and pollen.
- In animals to produce the gametes sperm and egg.
6
Q
What is sexual reproduction?
A
Reproduction that involves the fusion of male and female gametes (fertilisation).
7
Q
True or false, during sexual reproduction there is a mixing of genetic information which leads to variety in the offspring?
A
True - this is because every gamete is different.
8
Q
In asexual reproduction is there a mixing of genetic information?
A
No. Asexual reproduction only involves one parent (no fusion of gametes involved) - so there is no mixing of genetic information.
This means all the offspring are genetically identical aka clones.
NO VARIATION
9
Q
Asexual reproduction involves:
While sexual reproduction involves?
A
ASEXUAL - Mitosis
SEXUAL - Meiosis
10
Q
Meiosis versus Mitosis
A
- Meiosis - produces non identical offspring while mitosis produces identical offspring.
- After mitosis offspring have 46 chromosomes, after meiosis offspring have 23 chromosomes.
- Mitosis is involved in asexual reproduction and meiosis occurs during sexual reproduction.
- Mitosis produces 2 offspring but meiosis produces 4 offspring.
- They both result in the production of new offspring.
- They both include cell division.
- In both, DNA doubles.
11
Q
Asexual Reproduction versus Sexual reproduction:
sims and diffs
A
- Asexual involves one single parent while sexual reproduction involves more than one parent - a male and female gamete.
- Asexual reproduction - no mixing of genetic info, while sexual there is.
- Asexual reproduction - offspring are genetically identical, while sexual, offspring are not (so there is variation)
- They both result in the production of offspring
12
Q
Where does meiosis take place?
A
Only in reproductive organs.
Males - The testes
Females - The ovaries
13
Q
Meiosis produces how many cells while mitosis produces how many cells?
A
4 - meiosis
2 - mitosis
14
Q
Describe the process of cell division by meiosis to form gametes:
A
- In the cell in the reproductive organ, genetic information of the cell is copied within it.
- The cell now divides twice to form 4 gametes.
- In each gamete there is a single set of chromosomes.
- So each gamete is genetically different from each other.
- At fertilisation the gametes fuse to restore the number of chromosomes
15
Q
What happens after gametes have been formed by meiosis?
A
- Male and female gametes join at fertilisation to restore the normal number of chromosomes.
- This new cell is called a zygote which divides by mitosis and the number cells increases to form a ball of cells.
- This ball of cells is called an embryo.
- The cells of an embryo are all genetically identical to one another.
- As the embryo develops the cells differentiate.
16
Q
Advantages of sexual reproduction:
A
- SR produces variation in the offspring
- So if the environment changes variation gives a survival advantage by natural selection for the offspring with the advantageous characteristics.
- Natural selection can be sped up by humans in selective breeding to increase food production.
- Less time and energy efficient because do need to find a mate so is slower than asexual reproduction
17
Q
Advantages of asexual reproduction:
A
- Only one parent needed
- More time and energy efficient as there is no need to find a parent so is faster than asexual reproduction
- Many identical offspring can be produced when conditions are favourable.
- No variation produced in offspring so if the environment changes, there is no survival advantage amongst offspring - offspring could all die if conditions become unfavourable.
18
Q
Malarial parasites reproduce asexually when, and sexually when?
A
- They produce asexually in the human host.
- They produce sexually inside the mosquito.
19
Q
Fungi reproduce asexually when, and sexually when?
A
- Both sexually and asexually to produce spores.
20
Q
Plants produce seeds how?
A
- Through sexual reproduction
21
Q
Plants produce sexually when and asexually when?
A
- Plants produce seeds sexually.
- Plants such as strawberry plants reproduce asexually by runners.
- Plants such as daffodils reproduce asexually via bulb division.
22
Q
Where is DNA found?
A
DNA is found on chromosomes.
23
Q
What is a gene?
A
A small section of DNA on a chromosome.
24
Q
What chemical are chromosomes made from?
A
Chromosomes are made up from the molecule DNA.
25
What is the role of a gene?
To code for a particular sequence of amino acids which combine together to make a protein.
EG the blood type gene encodes a sequence of amino acids for the protein that determines blood type.
Remember:
Chromosomes are made up of Genes.
Genes are made up of DNA
And so the chromosomes can be said to be made from the molecule DNA.
26
What does DNA (Deoxyribonucleic acid) do?
DNA determines our inherited features.
27
Draw and label a diagram of DNA
28
What is meant by a genome?
The entire set of genetic material of an organism.
FOR EXAMPLE:
- The human genome is the entire genetic material that makes a human.
29
Describe the benefits of scientists studying the human genome (why is this important?).
3 reasons:
-** It allows for scientists to search for genes linked to different types of diseases.**
- It allows for us to understand and know how to treat inherited disorders.
- we can use the understanding of the human genome to trace human migration patterns from the past, allowing us to learn about our ancestry.
29
Describe the structure of DNA:
- A polymer consisting of two strands made from nucleotides, which each wrap around each other to form a double helix.
- These DNA strands are made up of monomers called nucleotides
- Nucleotides are made up of the phosphate group, sugar molecule and a base.
29
Draw and label the diagram of a nucleotide.
Must have:
- Phosphate group (circle)
- Sugar molecule (pentagon)
- Nitrogenous Base (rectangle)
INFO
- In DNA, the phosphate group, and the sugar molecule NEVER change, but bases do.
30
How many DNA bases are there?
4
A (adenine)
C (cytosine)
G (guanine)
T (thymine)
31
True or false, DNA strands are complementary?
True. The same bases always pair on the opposite strand.
C G
T A
32
TRUE OR FALSE?
The order of bases in a gene determines the order of amino acids in a protein, and thus the protein's shape and therefore its function,
TRUE.
33
What are proteins?
Polymers of amino acids.
(most proteins contain hundreds of amino acids joined together, but there are only 20 different amino acids in humans)
33
The specific order of the amino acid determines what.... which determines what....
The specific order of the amino acid determines the shape of the protein which determines the protein's function.
34
What is the order of amino acids in a protein determined by?
A gene codes for a particular sequence of amino acids which are put together to make a specific protein.
THAT SEQUENCE OF AMINO ACIDS
The sequence of amino acids in a protein is determined by the sequence of bases in the gene for that protein.
35
How do cells, at which the DNA is enclosed in read the DNA to know which amino acid to make?
- Each amino acid is coded for by a sequence of three bases.
- The cell at which the DNA is enclosed in reads the DNA sequence in triplets of bases.
- So each triplet codes/tells the cells to make 1 amino acid.
So if the arrangement of the bases was in a different order, a different amino acid would be created.
^^a chain of amino acids is known as a polypeptide.
36
Describe the process of protein synthesis.
Stage 1: Transcription
- The base sequence of the gene is copied into a complementary template molecule called mRNA.
- mRNA is a single stranded molecule and is used instead of DNA as DNA is too large to move out of the nucleus into the cytoplasm.
- So mRNA moves into the cytoplasm.
(Remember DNA is double stranded).
Stage 2: Translation
- mRNA molecule attaches to the ribosome in the cytoplasm.
- Amino acids are now brought on carrier molecules called tRNA to the ribosome.
- The ribosome reads the
triplets of bases on the mRNA and uses this to join the correct amino acids in the correct order.
- This forms a protein chain (polypeptide), and once this is complete it folds into its unique shape which enables it to do its job.
37
Mutation:
A random change in the sequence of bases in DNA (random change to a gene)
Mutations occur continuously. Most do not alter the protein, or they only alter the protein slightly so that its appearance and function is not changed.
38
True or false, mutations are continuous and random?
True - mutations happen all the time and they are random.
39
A change to a sequence of bases may affect the sequence of amino acids the base triplets codes for.
This may affect the protein formed.
However in some cases, a change to a base in a triplet has no effect on the overall structure of the polypeptide, suggest why.
Different bases may still code for that same amino acid.
This is why most mutations have no effect on the structure of a protein and its function.
40
Describe the consequences that may occur when the base of a gene coding for an enzyme changes.
A few mutations code for an altered protein with a different shape.
(base triplet changes, amino acid coded for changes so protein shape is wrong).
- An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
41
DNA has non-coding parts, and coding parts, true or false?
True, the non-coding parts switch genes on and off (they tell genes when to produce proteins).
42
How can mutations in the non-coding parts have negative effects?
- These mutations may affect how genes can be switched on or off.
- A gene may be turned on when it should be turned off.
- So the cell will produce a protein that it is not meant to have at that time.
- This may result in uncontrolled mitosis, leading to cancer.
43
True or false, most characteristics are controlled by many genes acting together?
True
44
What is an allele?
A different version of a gene - 1 allele is inherited from each parent.
An allele is a variant of a gene - it occupies a chromosome and remember each chromosome is inherited from each parent, which is why we have 2 versions of that gene.
- Look at your notes.
45
What is meant by the genotype?
A combination of alleles.
So like Cc will be a genotype, or pp will be a genotype.
46
True or false, alleles are either dominant or recessive?
True.
A dominant allele is an allele that will be expressed in the phenotype(shown with a capital letter)
A recessive allele is an allele that needs two to be expressed in the phenotype.
(shown with a lower case letter).
47
Dominant allele:
- Only one out of the two alleles is needed for it to be expressed and the corresponding phenotype to be observed.
48
Recessive allele:
- Two copies are needed for it to be expressed and the corresponding phenotype to be observed.
49
Heterozygous versus homozygous:
Heterozygous: when one of the alleles inherited is dominant and the other is recessive, eg (Ee)
Homozygous: when both of the alleles are the same ie both dominant or both recessive. (ee or Ee)
50
Phenotype:
The physical characteristics that are observed in an individual eg eye colour etc.
51
Give an example of characteristics that are a result of multiple genes interacting:
Height.
52
Give an example of two characteristics that are controlled by a single gene:
Fur and eye colour.
53
What is meant by cystic fibrosis?
Cystic fibrosis is a disorder of cell membranes caused by a recessive allele. (must have two cc alleles to have cystic fibrosis).
Cystic fibrosis is controlled by a single gene.
The allele for the normal cell membrane function: C
The allele for cystic fibrosis: c
If person A has a genotype of Cc (heterozygous - both dominant and recessive) they are a CARRIER.
If person B's genotype is CC they are homozygous for the dominant normal allele - so they are unaffected (no CF)
If person C's genotype is homozygous for the recessive allele 'cc' they have cystic fibrosis.
- Remember to read carefully how exams word the questions.
54
Why are punnet squares not accurate?
Because they are probabilities - all the offspring can have that disorder, or all of the offspring could not.
55
A punnet square should always include:
- Label of who the father/mother is
- 'Gametes'
- A ratio/percentage/fraction answering the question.
- Labelled genotype corresponding with each ratio.
56
What is meant by 'polydactyly'
An inherited disorder of having extra fingers or toes, caused by a dominant allele.
^So a person that is heterozygous for the dominant allele has polydactyly.
CC = affected
Cc = affected
cc = unaffected
^You cannot be a carrier of polydactyly, or any inherited disorder caused by a dominant allele.
57
What is meant by embryo screening?
What happens during it?
THE TWO TYPES OF EMBRYO SCREENING INCLUDE:
The process by which embryos are tested to see if they have the alleles for inherited disorders.
PROCESS:
1- The embryo is developed in a lab and cells from the embryo are taken for analysis (to see if they have the alleles for the inherited disorders).
2- DNA from the embryos in the womb are extracted and tested in a lab (this can result in miscarriages).
^Embryos which do not have the defective allele are implanted into the woman's uterus and develop into healthy offspring.
58
Embryo screening for:
x4
- It allows parents to choose whether to consider an abortion.
- Allows parents to prepare.
- Treating inherited disorders is expensive in the long term and e.s allows for this long-term cost to be saved.
- Reduces the number of people suffering from inherited disorders.
59
Embryo screening against:
x4
- Procedure can lead to miscarriage.
- It is expensive to carry out embryo screening.
- Could encourage people to pick desirable characteristics leading to 'designer babies'.
- A large amount of embryos are created but only a small amount are implanted into the woman. This means some healthy embryos are destroyed and some ppl think this is unethical.
60
What is meant by gene therapy?
The process by which scientists **correct** faulty alleles in order to treat inherited disorders.
(still experimental at the moment).
61
Is it true that family trees (family pedigrees) only show phenotype?
Yes, they only show phenotypes and they do not show genotypes.
^^We can use them to infer the phenotypes.
62
2 parents do not have a conditions but their offspring does, how do we know the condition is caused by a recessive allele?
- The two parents don't have the condition but the offspring does.
- So, the parents must be carriers for the defective allele of that condition.
- Because they are carriers, the condition must have been caused by a recessive allele.
- The child must have have inherited 1 recessive allele from each parent.
- Which is why the child is affected.
63
A parent has a condition and the other doesn't but the child does, how do we know the condition is caused by a dominant allele?
- 1 parent is affected and the other isn't.
- So the affected parent must be heterozygous while the unaffected parent must be homozygous for the recessive allele.
- The offspring must have inherited the defected dominant allele from the affected parent and the normal recessive allele from the unaffected parent.
- And so because the child has that condition but only has one recessive and one dominant allele, it shows that the condition is caused by a dominant allele.
64
Normal human body cells contain how many pairs of chromosomes?
23 pairs (46 in total)
- 1 of these chromosome pairs contain the genes which determine sex.
- 22 of the chromosome pairs contain the genes which determine inherited characteristics only.
65
Male sex chromosomes:
Female sex chromosomes:
Male = XY
Female = XX
so if you draw a punnet square for the inheritance of offsprings sex you will get a figure of 50% of all offspring being male and a 50% of all offspring being female or 1:1 change m:f.
- But these are just probabilities, all of the offspring could be male or all of the offspring could be female.
66
PART 2
67
What is meant by variation?
The differences in the characteristics of individuals in a population.
68
What causes variation in a population?
- The genes individuals have inherited (genetic causes). eg lobe(less) ears, eye colour
- The conditions individuals have developed in (environmental causes). eg piercings and tattoos
- A combination of genes and the environment. eg weight and height.
69
There is usually extensive variation within a population of a species, true or false?
True: for these reasons above.
70
What is a mutation?
A random change to DNA.
Mutations occur continuously.
- Most mutations have no effect on the phenotype.
- Some mutations can influence phenotype
- A small number of mutations determine a phenotype.
71
Key idea on mutations:
- Very rarely, a mutation can lead to a new phenotype.
HOW CAN A MUTATION LEAD TO A NEW PHENOTYPE?
- This occurs if the mutation causes a phenotype that is advantageous
- Natural selection will mean it becomes the most common phenotype amongst a species very quickly.
- Because organisms without the advantageous phenotype die away.
72
RECALL:
- All variants arise from mutations and that:
- most have no effect on the phenotype;
- some influence phenotype;
- A small amount determine phenotype.
GOOD? yes
73
What is meant by evolution?
- A change in the inherited characteristics in a population over time through a process called natural selection which may result in the formation of a new species.
74
What does the theory of evolution by natural selection state?
All species of living things have evolved from simple life forms that first developed **more than three billion years ago**.
75
Explain how evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment.
(Explain the process of evolution by natural selection).
- There is extensive genetic variation with a population of a species.
- When a change to an environment occurs, the animals in the species that have the advantageous alleles will survive to reproduce fertile offspring while the animals who don't have these alleles die off.
- These advantageous alleles are passed onto the offspring of that species.
- So over many generations the advantageous alleles become widespread and more common.
- The population of that species has evolved.
76
True or false, if two populations of one species become so different in phenotype they can no longer interbreed to produce fertile offspring so they have become two new species?
What is this known as?
True.
This is known as speciation. (define)
Speciation is the process by which two populations of species have become so different in phenotype that they can no longer interbreed to produce fertile offspring.
77
How did the work of Gregor Mendel lead to out understanding of genetics?
- In 1800s, Mendel carried out thousands of breeding experiments on pea plants.
- At the time, scientists did not understand how inheritance worked - many thought that characteristics were blended when they were inherited.
- Mendel observed different characteristics in pea plants and realised that characteristics are not blended during inheritance, but rather they are determined by **inherited units**.
- He states that these units do not change when they are passed onto descendants.
- These units are now known as genes.
- Mendel also noticed that some of these characteristics can be masked and reappear in later generations.
- These are called recessive alleles.
- Mendel published his research in a scientific paper, but many scientists still held onto the belief that characteristics inherited are blended.
- So his work was forgotten.
(So Mendel discovered genes and recessive alleles).
78
Why was the importance of Mendel's discovery not recognised until after his death?
- Scientists still believed that characteristics inherited were blended.
- In the late 1800s scientists looked at how chromosomes behaved during cell division, and around the same time scientists rediscovered Mendel's work on genetics.
- They realised that chromosomes behaved in a similar way to these units/genes.
- From this, they discovered that genes must be located on chromosomes.
- In the mid 1900s scientists determined the structure of DNA and how genes functioned.
79
What is meant by genetic engineering?
The process of modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
80
State 2 examples of genetic engineering:
- Plant crops have been genetically engineered to be resistant to diseases.
- Plant crops have been G.E produce bigger better fruits.
- Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat type one diabetes.
81
Describe the process of genetic engineering:
* Enzymes are used to isolate the desired gene of an organism.
*This gene is inserted into a vector, usually a bacterial plasmid or a virus.
* The vector now divides by mitosis to produce genetically identical offspring containing the gene.
*The desired gene is purified and transferred from the vector to the cells of the target organism at an early stage of the organism's development.
* This allows for the cells to receive the transferred gene so the organism develops with the desired characteristics.
82
Advantages and concerns of genetic modification of crops (GM crops):
ADVANTAGES
- Greater yields of crops will be produced and this can end world hunger.
- Can prevent extinction of rare plants
CONCERNS
- People question whether GM crops are safe for insects.
- We do not fully understand the effects of GM crops on human health.
83
Genetically modifying crops:
An example of how plants have been genetically modified and the advantage of this:
- Some plants have been genetically modified to be resistant to insects and herbicides.
- This will increase the yield of these crops as less crops will die.
- These crops are known as 'GM' crops.
84
Gene therapy:
what is it?
advantages?
disadvantages?
Gene therapy: The process by which genetic engineering may be used to cure inherited disorders.
- Gene therapy involves transferring the normal genes into a patient so correct proteins are produced.
ADVANTAGES
- May be used to cure inherited disorders in humans.
DISADVANTAGES
- The long term effects of it is not known.
85
Genetic engineering summary: advantages and disadvantages
ADVANTAGES
- Greater yield of crops produced which can end world hunger.
- In agriculture it may allow crops to grow in different conditions.
- In medicine it can be used for mass production of certain hormone using certain microorganism to cure inherited diseases.
DISADVANTAGES
- GM crops are infertile and the genes could spread to wild plants leading to infertility in other species which affects the environment.
- We do not entirely understand the effects of GM crops on human health.
86
PLANT CLONING:
- Cuttings
- Tissue culture
How are plants cloned by cuttings?
CUTTINGS:
- A small piece of plant is cut and removed and the cut end is dipped into rooting powder.
- This part of the plant produces roots and a new plant which is genetically identical to the parent.
TISSUE CULTURE
- The organism is cut into many small pieces,
- These pieces are incubated in plant hormones using an agar gel plate,
- These plant hormones stimulate cells of these pieces to grow and develop into fully grown clones.
^^
- The conditions that this takes place in must be sterile.
87
Plant cloning:
Cuttings and Tissue culture advantages and disadvantages
CUTTINGS +
- Quick process
- Easy process - doesn't require specialist skills.
- It is a cheap process
CUTTINGS -
- Limited variation
- Correct growing conditions are required (rooting powder, moist conditions, correct temperature)
- A large quantity of clones isn't produced.
- Gardeners can be certain that they will get the characteristics they want because the offsprings are clones
TISSUE CULTURE +
- Preserves rare species of plants
- Lots of identical offspring produced
- Gardeners can be certain that they will get the characteristics they want bc the offsprings are clones.
TISSUE CULTURE -
- A more technical process
- Correct growing conditions required, ie conditions must be sterile - this is so we do not introduce harmful microorganisms such as bacteria/fungi.
- Limited variation
88
How can animals be cloned - the 2 methods:
- Embryo transplants
- Adult cell cloning
89
Describe the process of cloning via embryo transplants:
- Start with a sperm and an egg cell from organisms with the desired characteristics.
- Fertilise the sperm and egg cells and allow it to develop into an early stage embryo.
- Now use a glass rod to split the embryo into two before the cells in the embryo begin to specialise.
- Transplant each embryo into two host mothers, in which these embryos will grow and develop into identical offspring.
90
Describe the process of adult cell cloning:
- Take a body cell from the desired organism (this could be a skin cell).
- Remove the nucleus from this cell, the nucleus contains the genetic information from the animal that we are cloning.
- Now take an unfertilised egg cell from the same species.
- Remove the nucleus from the unfertilised egg and throw this away.
- The unfertilised egg now contains no genetic material at all so we can insert the nucleus of the original adult cell into the unfertilised egg cell.
- Now we give this egg cell an electric shock.
- This causes the egg cell to divide to form an embryo - these embryo cells contain the same genetic information as the adult cell we started with.
- When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue development.
- The host mother then gives birth to the adult clone.
91
Why does the clone look nothing like the host mother?
It does not contain any of the genetic material of the host mother.
REMEMBER TO SAY **HOST** MOTHER
92
Adult cell cloning advantages and disadvantages:
A
- Cloning from an adult cell so we can be certain of the characteristics that the clone will have, unlike embryonic cloning.
D (applies to embryonic cloning)
- Reduced variation
- Could pass on genetic diseases!!
- Expensive
- Requires specialist skills
93
Advantages of embryonic cloning:
- We can produce lots of offspring with inherited desired characteristics.
94
Describe Darwin's theory of evolution by natural selection.
- In the 1800s Darwin took part in an expedition around the world and collected a vast number of different animals and plants - he was fascinated by the variety amongst living organisms that he saw and began to wonder how this variety developed.
- Darwin spent many years studying geology and fossils - these fossils showed that many species of animals and plants today are similar to extinct species.
- After many years of experimentation and discussion, Darwin began to devise the theory of evolution by natural selection.
TOEBNS:
* Individual organisms within a particular species show a wide range of variation for a characteristic.
* Individuals with characteristics most suited to the environment are more likely to survive to breed successfully if a change to the environment occurs.
* The characteristics that have enabled these individuals to survive are then passed on to the next generation.
(just change alleles, to characteristics).
95
Why was Darwin's theory only gradually accepted?
x3 reasons
In 1859, Darwin published his ideas in a book called ''On the Origin of Species''.
His views and ideas were only gradually accepted because:
- A lot of people believed that **God made the animals and plants that lived on Earth and Darwin's Theory challenged that**
- Many people felt there was **not enough evidence** to back up Darwin's theory.
- The mechanism of inheritance and variation was not known until 50 years after the theory was published.
96
Describe how Lamarck suggested that species change, and why Lamarck's theory is incorrect.
Lamarck suggested that when a characteristic is regularly used it becomes more developed.
This strengthened characteristic is then passed onto offspring.
(Eg the Giraffe neck length theory).
WHY IS THIS WRONG?
- Changes that occur an organism's lifetime cannot be passed onto offspring.
97
How did Alfred Russel Wallace contribute to our understanding of evolution?
Alfred Russel Wallace independently proposed the theory of evolution by natural selection after having studies warning colouration in animals.
He then published joint writings with Darwin (after they realised they had the same theory) in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year.
Wallace also came up with the theory of speciation.
SUMMARY
- Speciation theory
- His work on warning colouration in animals.
98
How do new species form?
SPECIATION:
- Variation exists within a population due to genetic mutations.
- Initially, all species in a population can breed so mutations can spread throughout the population.
- Then geographical isolation occurs and the species is split into two groups by a geographical barrier.
- So interbreeding can no longer occur between the two groups of species so mutations cannot spread between them.
- Over time natural selection will favour different advantageous alleles on the two sides of the barrier, so variation increases.
- Over many generations the phenotypes of the two groups becomes so different that the species are no longer able to interbreed to produce fertile offspring.
- So speciation has occurred.
99
READ MENDEL NOTES
100
Summary:
Mendel - Units of inheritance
Wallace - Speciation theory and his work on animal warning colours
Darwin - The theory of evolution
Lamarck - The idea that when a characteristic is regularly used it becomes more developed and strengthened so is passed onto offspring.
101
What is a fossil?
The remains of organisms from millions of years ago, which are found in rocks.
102
3 ways at which fossils are formed:
* From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent (temp too cold, not enough oxygen, not enough water).
* When parts of the organism are replaced by minerals as they decay.
* As preserved traces of organisms, such as footprints, burrows and rootlet traces.
103
Why is the fossil record incomplete?
- The fossil record doesn't account for all life.
- Because many early forms of life were soft-bodied, which means that they have left few traces behind.
- These traces they may have left behind have been mainly destroyed by geological activity.
- This is why scientists cannot be certain about how life began on Earth.
104
What can we learn from fossils?
How much or how little different organisms have changed as life developed on Earth.
105
What is meant by an extinct species?
Why can species become extinct?
A species where there are no remaining individuals of that species alive.
This can occur due to
- New disease/New predators.
- Catastrophic events.
- Change in environment
- Competition: If a new more successful species evolves and competes with it.
106
Students should be able to extract and interpret information from charts, graphs and tables such as evolutionary trees.
107
Describe how bacteria can become resistant
GIVE AN EXAMPLE OF AN ANTIBIOTIC RESISTANT BACTERIA:
Why can bacteria evolve rapidly?
- Because they reproduce at a fast rate.
- Bacteria can evolve rapidly because they reproduce at a fast rate.
- Mutations of bacterial pathogens produce new strains of bacteria.
- Some strains might be resistant to antibiotics, and so are not killed.
- They survive and reproduce, so the population of the resistant strain rises.
- The resistant strain will then spread because people are not immune to it and there is no effective treatment.
EXAMPLE - MRSA
108
What kills bacteria?
Antibiotics.
109
What three ways can we reduce the risk of antibiotic resistance?
* doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
* patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.
* the agricultural use of antibiotics should be restricted.
110
Why is it hard for doctors to keep up with the emergence of new antibiotic strains?
- The development of new antibiotics is costly and slow.
- It is unlikely to keep up with the emergence of new resistant strains given that bacterial strains evolve rapidly.
111
How are organisms classified based on their characteristics?
By who?
CARL LINNAEUS: Traditionally, living things have been characterised into groups depending on their structure and characteristics. This is known as the Linnaean system (STRUCTURE AND CHARACTERISTICS)
These are the categories of the L.S:
- Kingdom
- Phylum
- Class
- Order
- Family
- Species
Remember; King Phillip Came Over For Good Soup)
HOW ARE ORGANISMS NAMED?
- The binomial system of genus and species.
INFO:
- Linnaeus divided all living organisms into two kingdoms: the animal kingdom and the plant kingdom. ^^these are all divided into the smaller categories which are shown above.
When we write the binomial name, write the Genus and write the Species and underline both!
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1) What is the Linnaean classification system based on?
2) What scientific advancements have changed this (Carl Woese)?
1) Physical characteristics and structure.
2) The Three Domain system by Carl Woese:
As evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes, new models of classification were proposed.
Due to evidence available from chemical analysis there is now a ‘three- domain system’ developed by Carl Woese. In this system organisms are divided into:
* archaea (primitive bacteria usually living in extreme environments)
* bacteria (true bacteria)
* eukaryota (which includes protists, fungi, plants and animals).
So essentially due to development of microscopes and our knowledge on biochemical processes, there led to a development in the L.S to become the three domain system (no longer KPCOFGS but rather, archaea, bacteria, eukaryota).
113
What are evolutionary trees?
How are they made for living organisms and extinct ones?
- Evolutionary trees are a method used by scientists to show how they believe organisms are related.
- They use current classification data for living organisms and fossil data for extinct organisms (this can be a problem because the fossil record for many species are incomplete).
COMPLETE PQ ON EVOLUTIONARY TREES.
(for living organisms: classification data and for extinct organisms: fossil record data)
114
Describe the process of selective breeding to produce organisms with desirable characteristics.
- Parents with desired characteristics are chosen and bred together.
- They pass on these desired characteristics onto some of their offspring and now these offspring have varied characteristics.
- From this offspring a male and female with the most desirable characteristics are selected and crossed to reproduce more offspring with the most desirable characteristics.
- This process is repeated several times until the desirable characteristic is achieved.
LOOK AT QUESTION.
115
Why are some animal selectively bred?
- To be more gentle
- To have more fur
116
What is one problem of inbreeding?
- It increases the likelihood of recessive inherited disorders being passed on.
117
What is meant by a clone?
Offspring of a parent that is genetically identical to the parent and is produced via asexual reproduction.
YAY YOU DID IT!
