Inheritance,Variation and Evolution. Flashcards
1
Q
What is DNA?
A
Deoxyribonnucleic Acid.
Chemical that all of the genetic material in a cell is made up from.
2
Q
What does DNA contain?
A
Coded information, all the information to put an organism together to make it function.
3
Q
What does your DNA determine?
A
What inherited characteristics you have.
What proteins the cell produces eg:haemoglobin and keratin. That in turn determines what type of cell it is eg:red blood cell and skin cell etc
4
Q
Where is DNA found?
A
Nucleus of animals and plant cells in really long structures called chromosomes.
5
Q
What do chromosomes come in?
A
Pairs.
6
Q
What is DNA made up of?
A
It is a polymer.
Made up of two strands, coiled together in the shape of a double helix.
7
Q
Define gene.
A
Small section of DNA found on a chromosome.
8
Q
What does each gene code for?
A
A particular sequence of amino acids which are put together to make a specific protein.
9
Q
How many amino acids are used to make up thousands of different proteins?
A
20
10
Q
What is the job of a gene?
A
Tells cells in what order to put the amino acids together
11
Q
Define Genome.
A
Term for the entire set of genetic material in an organism.
12
Q
What have scientists worked out?
about the genome?
A
The complete human genome.
Understanding the human genome is a really important tool for science and medicine for many reasons.
13
Q
What does understanding of the genome allow scientists to do?
A
To identify genes in the genome that are linked to different types of disease.
Knowing which genes are linked to inherited disease could help us understand them better and develop effective treatments.
Science look at genome to trace migration of certain populations of people around the world.
All modern humans descended from common ancestor who lived in Africa, but humans are found all over the planet.
Human genome is identical in all humans but as different populations of people migrated from Africa they gradually develop tiny differences in their genomes.
By investigating these differences, scientists can work out when new populations split off in a different direction and what route they took.
14
Q
What are DNA strands made from?
A
They are polymers, made up of lots of repeating units called nucleotides.
15
Q
What does each nucleotide consist of?
A
One sugar molecule, one phosphate molecule and one “base”
16
Q
What do the sugar and phosphate molecules in the nucleotides form?
A
A backbone, to the DNA strands.
The sugar and phosphate molecules alternate.
One of four different bases -A,T,C or G- joins to each sugar.
17
Q
What does each base link up to?
A
A base on the opposite strand in the helix.
18
Q
Which bases pair up with each other?
A
A pairs up with T
C pairs up with G
This is called complimentary base pairing.
19
Q
What is complimentary base pairing.
A
Order of bases in a gene that decides the order of amino acids in a protein.
20
Q
What is each amino acid coded for?
A
By a sequence of three bases in a gene.?
21
Q
Amino acids join together to make what?
A
Various proteins, depending on the order of the genes bases.
22
Q
What controls whether a gene is expressed or not.
A
Parts of a DNA that does not code for proteins, some of these non coding parts switch genes off so they control whether the gene is expressed. (used to make a protein)
23
Q
Where are proteins made?
A
In the cell cytoplasm on tiny structures called ribosmomes.
24
Q
To make proteins what do ribosomes do?
A
They use the code in the DNA. DNA is found in the nucleus and can’t move out of it as it is really big. So the cell needs to get the code from the DNA to ribosomes.
This is done using mmolecule mRNA which is made by copying the code from DNA.
The mRNA acts as a messenger between DNA and ribosome. It carries the code between two.
The corect amino acids are brought to ribosomes in the correct order by carrier molecules.
25
What allows the protein to perform the task it is meant to do?
When a chain of amino acids has been assembled it fold into a unique shape which allows it to perform the task it is meant to.
26
Give examples of different types of proteins.
Enzymes,hormones and strucutral proteins.
27
Define enzymes.
Act as a biological catalyst to speed up chemical reactions in the body.
28
Define hormones.
Used to carry messengers around the body. EG: Insulin is a hormone released into the blood by the pancreas to regulate the blood sugar level.
29
Define structural proteins.
Are physically strong. EG: collagen is a structural protein that strengthens connective tissues like ligaments and cartilage.
30
Define mutations.
Changes to genetic code, occasionly a gene may mutate.
| A mutation is a random change in an organsisms DNA they can sometimes be inherited.
31
When do mutatations occur?
Continuosly and spontaneously. Eg: when a chromosome isn't replicated properly however the chance of mutation is increased by exposure to certain substances or some types of radiation.
32
What does a mutation change?
Sequence of DNA bases in a gene which produces a genetic variant. As the sequence of DNA bases codes for sequence of amino acids that make a protein mutations to a gene lead to changes in the protein it codes for.
33
How much affect do mutations have?
Little or no effect on protein. Some will change it to such a small extent that its function/appearance is unnafected.
34
What affects can some mutations have?
Seriously affect a protein.
Mutation will code for an altered protein with a change in its shape.
This could affect its ability to perform function.
35
Example of how the mutation can affect a protein?
If shape of an enzyme active site is changed its substrate may not bind to it.
Structural proteins like collagen could lose their strength if their shape is changed making them useless to provide structure and support.
36
What happens if there is a mutation in non-coding DNA?
Alters how the gene is expressed.
37
Give the three different types of mutations
Insertions
Deletions
Substitutions
38
Describe insertions.
New base is inserted into DNA base sequence where it shouldn't be.
An insertion changes the ways the groups of three bases are read which can change the amino acids they code for.
Insertions can change more than one amino acid as they have a knock on effect on bases further in the sequence.
39
Describe Substitutions.
when a ransom base in the DNA base sequence is changed to a different base.
40
Describe Deletions.
When a random base sequence is deleted from the DNA base sequence.
Like insertions they can change the way that the base sequence is read and have knock on effects further down the sequence.
41
Define sexual reproduction.
genetic information from two organisms a father and mother is combined to produce offspring which are genetically different to either parent. Involves fusion of male and female gametes, as there are two parents te offspring contain a mixture of their parents genes.
42
In sexual production what do the mother and father produce?
Gametes, by meiosis eg: egg and sperm cells in animals.
43
In humans how many chromosomes does each gamete contain?
23 chromosomes half the number of chromosomes in a normal cell. Instead of having having two of each chromosome a gamete has just one each)
44
How do the gametes then create a cell with the full number of chromosomes?
The egg the mother and the sperm the father, then fuse together (fertilisation) to form a cell with the full number of chromosomes half from the father and half from the mother.
45
Why the offspring inherits features from both parents.
its recieved a mixture of chromosomes from its mum and its dad and its the chromosomes that decide how you turn out.
46
What produces a variation in offspring?
Mixture of genetic information produces variation in offspring.
47
How do flowering plants reproduce?
They have egg cells, but the sperm is known as pollen.
48
quick asexual reproduction
Theres only one parent so the offspring are geneticaly identical to their parent.
It happens by mitosis, an ordinary cell makes a new cell by diving in two.
49
In asexual reproduction what does the new cell contain?
Exactly the same genetic information as the parent cells its called a clone.
50
Definition of asexual reproduction.
there is only one parent.
no fusion of gametes
no mixing of chromosomes and no genetic variation between parent and offspring.
the offspring are genetically identical to their parent so they are clones.
51
What reproduces asexually?
Bacteria,some plants,some animals.
52
To make gametes with only half of the original number chromosomes what occurs?
Cells will divide by meiosis. It involves two cell divisions.
53
In humans where does meiosis occur.
Reproductive organs (the ovaries in the femals and the testes in the males)
54
Describe the process of meiosis.
-before cell starts to divide it duplicates its genetic information forming two armed chromosomes.
-one arm of each chromsomeis an exact copy of the other arm.
-after replication the chromosomes arrange themeselves into pairs.
-in the first division in meiosis the chromosome pairs line up in the centre of the cell.
-the pairs are then pulled apart so each new cell only has one copy of each chromosome.
some of the fathers chromosomes and some of the mothers chromosome go into each new cell.
-in the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
-you get 4 gametes each with only a single set of chromosomes in it.
-Each of the gamete is genetically different from the others as chromosomes get shuffled up in meiosis and each gamete only get half of them.
55
After two gametes have fused during fertilisation what happens to the new cell?
new cell divides by mitosis to make a copy of itself.
mitosis repeats many times to make lots of cells in an embryo
as the embryo develops the cells differentate into the different types of specialised cell that makes a whole organism
56
Give four advantages of sexual reproduction
-offspring have a mixure of two sets of chromosomes.
the organism inherits genes and features from both parents which produces variation in offspring.
-Variation increases the chance of species surviving a change in enevironment. While a change in environment may kill some, it's likely variation will lead to some offspring being able to survive in new environment so they have a survival advantage.
-individuals have characteristics which make them better adapted to environment they have beter chance of surviving. So are more likely to breed succesfully and pass genes and characteristics. Thus known as antural selection.
-Use selective breeding to speed up natural selection. This allows us to produce animals with desirable characteristics. Selective breeding when inidviduals with desirable charachteristics are bred to produce offspring with desirable charachterisitics So we can increase food production eg:breeding animals which produce lots of meat.
57
Asexual reproduction advantages.
Only needs one parent
Uses less energy than sexual reproduction, as orgainisms don't have to find a mate.
faster than sexual reproduction
Many identical offspring can be produced in favourable conditions
58
Does the parasite which causes malaria reproduce asexually or sexually?
Malaria is caused by a parasite thats spread by mosquitos.
- When a mosquito carrying the parasite bites a human the parasite is transferred to a human.
- The parasite reproduces sexually wen in the mosquito and asexually when in the human host.
59
Does fungus produce asexually or sexually?
both.
These species release spores which can become new fungiwhen they land in a specific place.
Spores can be produced sexually and asexually.
Asexually produced spores form fungi that are genetically identical to the parent fungus.
Sexually produced spores introduce variation and are produced in response to unfavourable change in environment increasing the chance the population will survive the change.
60
Give an example of a plant reproducing asexually.
| -strawberry
Strawberry plants produce runners.
They are stems that grow horizontally on the surface of the soil away from the plant.
At various points along the runner a new strawberry plant forms that is identical to original.
61
Give an example of a plant reproducing asexually.
| -bulbs
plants that grow from bulbs eg daffodils,
New bulbs can form from main bulb and divide off
each new bulb can grown into a new identical plant.
62
What is the role of all 22 chromosomes and the 23rd?
22 are matched pairs of chromosomes that controll charachteristics
23 pair are labelled XY or XX they are the two chromosmes that decide your sex
63
What is the male chromosome?
XY
| Y chromosomes cause male characteristics
64
What is the female chromosome?
XX
| combination of two X allows female charateristics to develop.
65
When making sperm what happens?
X and Y chromosomes are drawn apart om the fist divsion of meiosis
50% chance each sperm gets an x chromosome and 50% chance it gets a y chromosome.
66
When making eggs what happens?
Original cell has 2 x chromosomes.
| So all the eggs have one x chromosome
67
What do genetic diagrams show?
Models sued to show all the possible genetic outcomes when you cross together different genes or chromosomes.
68
What genes you inherit control what?
What characteristics you develop.
69
What do different genes control?
Different characteristics some characteristcs are controlled by a single gene eg:mouse fur colour and red green colour blindess in humans.
70
What are some characteristics controlled by?
A single gene, eg:mouse fur colour, red green colour blindless in humans
71
What are most characteristics controlled by?
Several genes interacting,
72
What is an allele?
Different versions of a gene. There are 2 alleles for every gene in your body (one on each chromosome in a pair.)
73
Define homozygous?
When an organism has two alleles for a partigcualr gene that are the same then its homozygous for that trait
74
What is heterozygous?
If 2 alleles for a particular gene are different.
75
Define the term dominant allele.
If two alleles are different only one can determine what characteristics are present. The allele for the characteristics that is shown is the dominant allele. (use a capital letter for dominant)
76
Define recessive.
represented with a small letter and it is when two alleles are different and the allele which did not determine characteristics
77
How can an organism display a reccesive characteristic?
both alleles must be recessive (cc)
78
How can an organism display a dominant characteristic?
CC or Cc
| dominant allele overrules the recessive one if plant or aniamal is heteroygous
79
define geontype
Combination of alleles you have
80
Define phenotype
When your alleles work at a molecular level to determine what charachteristics you have.
81
What does a 1:1 ratio mean?
Parent with one dominant allele heterozygous Hh is crossed with parent with two recessive alleles homozygous recessive hh
82
What is cystic fibrosis?
genetic disorder, of the cell membranes.
| Results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas.
83
Which allele causes cystic fibrosis?
Reccessive allele "f" carried by 1 person in 25.
84
Who will have the disorder cystic fibrosis?
Its recessive so people with only one copy of the allele won't have the disorder.
They are known as a carrier.
For a child to have cystic fibrosis both parents must be either carriers or have the disorders themselves.
85
What is the chance of having cystic fibrosis?
1 in 4 chance, if both parents are carriers
86
What is polydactyly?
Genetic disorder where a babys born withextra fingers or toes.
It doesn't cause any other problems so isn't life threatening.
87
What is polydactyly caused by?
dominant allele D
can be inherited if just one parent carries the deffective allele.
The parent that has the defective allele will have the condiiton too since the allele is dominant.
88
Chance of a child having polydactyly if one parnt has one D allele
50%
89
What is invitro fertilisation?
Embryos are fertilised in a laboratory and then implanted into the mothers womb.
90
Can Embryos be screened for genetic disorders?
Before the fertilised embryo is implanted into the mothers womb its possible to remove the cell from ech embryo and analyse its genes.
Many genetic disorders can be detected in this way such as cystic fibrosis.
Possible to get DNA from an embryo in the womb and test that for disorders.
For embryos produced by IVF after screening embryos with bad alleles would be destroyed.
For embyos in the womb screening would lead to the decision to terminate the pregancy.
91
Reasons against embryonic Screening.
- implies that all people with genetic problems are undesirable which could increase predjudice.
- may come to apoint where everyone wants to screen there embryos so they can pick the most desirable eg:blue eye blonde hair
- screening is expensive
92
Reasons for embryonic screening
- it will help stop people suffering
- treating disorders will cost the government and tax payers a lot of money.
- laws to stop it going too far
- Parents cannot even select the sex of their baby unless its for health reasons.
93
Who was gregor mendel?
Austrian monk who trained in mathematics and natural history at the university of vienna.
On his garden plot at the monastery in mid 19th century mendel noted how charachteristics in plants were passed on from one generation to the next.
94
When was mendel's results published?
1866, and became foundation on modern genetics
95
What had mendel shown?
Height characteristics in pea plants were determined by seperately inherited "heritary units" passed on from each parent. The ratios of talla dn dwarf plants in the offspring showed that the units fro tall plants T was dominant over the unit for dwarf plants t.
96
Describe the three conclusion mendel reached?
- characteristics in plants are determined by hereditary units.
- Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent.
- Hereditary units can be dominant or recessive if an individual has both dominant and the recessive unit for a characteristic the dominant characteristic will be expressed.
97
How has mendels work contributed to the inderstanding of genes?
- In the late 1800s scientists became familiar with chromosomes. They were able to understand how they behaved during cell division.
- Early 20th century, scientists realised similiarities in the way that chromosomes and mendel "units" acted. Based on this it was proposed that these units were found on the chromosomes. We now know these units as genes.
- 1953, structure of DNA was determined this allowed scientists to go and see exactly how genes worked.
98
Why did the importance of mendel work wasn't realised straight away.
- had no understanding about genes DNA and chromosomes.
- didn't have background knowledge to understand his findings
- wasn't until after death until people relaised his work was important
99
What is variation?
Differences in the characterisics of individuals in a population. there are two types of variation genetic variation and environmental variation.
100
Why do plants and animals have characteristics similar to their parents?
because an organism characteristics are determined by the genes inherited from their parents
these genes are then passed on in gametes from which the offspring develop.
101
What causes genetic variation?
combining of two genes, no two of the species are genetically identical.
-the environment including the conditions that organisms live and grow in also causes differences between members of the same species (environmental variation)
102
What characteristics are determined only by genes?
eye colour, blood group, inherited disorders.
103
Give an example of how environmental variation influences characteristics?
A plant grown in plently of sunlight is luscious and green but the same plant grown in darkness would graw tall and spindly have yellow leaves
104
examples of environmental variation
getting a suntan, having yellow leaves,
105
What characteristics are a mixture of genetic and environmental factors?
body weight, height,skin colour,condition of teeth,academic or athletic prowess
for example maximum height that an anminal or plant could grow is determined by its genes, but whether it actually grows that tall depends on its environment(how much food it gets)
106
What effects can mutations have?
small influence on phenotype so only alter characteristics slightly.
but it is very rare, mutations can result in a new phenotype being seen in a species.
107
What happens if the environment changes and the new phenotype makes an indiviudal more suited to the new environment?
it can become common throughout the species relativley quickly by natural selection
108
Define the theory of evolution.
All of todays species have evolved from a simple life forms that first started to develop over three billion years ago
109
What did Charles Darwin discover?
Theory about evolution.
Used observations from around the world trip along with experiments discussions and new knowledge of fossils and geology to suggest the theory of evolution by natural selection.
110
What did Darwin know?
Organisms in a species show wide variation in their characteristics which was called phenotypic variation.
-Organisms had to compete for limited resources in ecosystems.
111
What did Darwin conclude?
-organisms with the most suitable charateristics for the emvironment would be more succesful competitiors and would be more likely to survive this is called SURVIVAL OF THE FITTEST
The succesful organisms that survive are more likely to reproduce and pass on genes for the charcateristics that made them succesful to their offspring.
112
According to Darwin what happens to organisms that are less well adapted?
Less likely to survive and reproduce so less likely to pass on genes to offspring.
Overtime beenficial characteristics become more common in the population and the species changes-it evolves.
113
Why wasn't Darwins theory perfect?
Relevant scientific knowledge wasn't available at the time, he couldn't give a good explanation for why characteristics appeared or how individual organisms passed on beneficial adaptations to offspring.
114
What have we built on to Darwins theory?
We now know that phenotype is controlled by genes.
New phenotypic variations arise because of genetic variants produced by mutations.
Beneficial variations are passed on to future genrations in the genes that parents contribute to their offspirng.
115
Quickly summarise the meaning if speciation.
Over a long period of time the phenotype of organisms can change so much because of natural selection that a completley new species is formed
116
When does speciation happen?
when populatiosn of the same species change enough to become reproductivley isolated (they can interbreed to produced fertile offspring)
117
Define extinction?
When no individuals of species remain.
| The fossil record contains many species that don't exist an more they are extinct.
118
Why species become extinct?
- environment changes too quickly eg:destrcution of habitat
- a new predator kills them all eg a human hunting them
- a new disease kills them
- they can't competer with another new species for food
- a catastrophic even happens and kills them all eg:volcanic eruption or collision of asteroid
119
Why are the dodos now extinct?
humans not only hunted them, but introduced other animals which ate all their eggs and we also destoryed forest where they lived
120
Why was darwins theory super controversial?
went against common religious beleifs about hw life developed on Earth. It was the first plausible explanation fo the existence of life on Earth without the need for the Creator.
Couldn't explain these useful new charateristics appeared or how they were passed on from individual organism to offspring. As he didn' know about mutations or genes weren't dsicovered until 50 years after his theory was published.
Not enough evidence to convince scientists, not many other studies had been done into how oragnisms changed overtime.
121
What was Lamarck's theory?
Jean Baptiste Lamarck 1744-1829, argued that changes an organism aqquires during its lifetime will be passed on to its offspring
he thought if a characteristic was used a lot by organism then it would be more developed during lifetime and theoffspring would also have this characteristic.
122
Give an example fo Lamarcks theory
Rabbit used it legs to run from predator then its legs would grow longer. The offspring would then also have long legs
123
Why scientists have different hypothesis?
different religious beliefs
| influenced by different people
124
Why was lamarcks theory rejected?
Experiments didn't support his hypothesis.
125
Why did the discovery of genetics support Darwin?
Provided and explanation for how organisms born with beenficil characteristics can pass them on via genes.
Other evidence was found by looking at fossils at differnet ages which shows changes in organisms devleoped slowly over time.
The discovery of hwo bacteria are able to evolve to become resistant to antibiotics also supports evolution by natural selection
126
What is selective breeding?
Humans artificially select the plants or animals that are going to breed so that th genes for particular characteristics remain in the population.
They are selectivley bred to develop features that are useful or attractive.
127
Examples of selective breeding.
Animals that produce more meat or milk.
Crops that are disease resistant
Dogs with good gentle temperament
Decorative plants with big or unusal flowers
128
Describe the process of selective breeding.
From existing stock select the ones which have characteristics you want.
breed them with each other
select the best of the offspring and breed them together.
continue this process over several generations and the desirable trait gets stronger. Eventually all offspring will have characteristics.
129
In agriculture how is selective breeding used?
Imrprove yields.
eg: improve meat yields a farmer could breed buls and cows with best characteritics for meat after doing this for several gens farmer would get cows with high yield
130
Main problem with selective breeding?
| inbreeding
reduces the gene pool -Number of different alleles in a population
As farmer keeps breeding from best animals or plants which are all closely related (inbreeding)
131
Problems of inbreeding.
health problems as more chance of organism inheriting harmful gentic defects when the gene pool is limited.
Some dog breeds are susceptible to certain defects because of inbreeding eg:pugs have breathing problems.
132
Main problem with selective breeding?
| new disease
New disease, as not much variation in the population.
All stock closely related to each other so one is killed then rest succumb to it.
selective breeding = reduction in number of different alleles = less chance of any resistant alleles being present in population
133
What is genetic engineering?
transfer a gene responsible for desirable characteristics from on organism genome into another organisms so it also has the features.
134
How is the process of genetical engineering taken out?
Useful gene is isolated from one organism genome using enzymes and is inserted into a vector.
Vector is ussually a virus or a bacterial plasmid depending on the type of organism that the gene is being transferred to.
When the vector is intorduced to the target organism the useful genes is inserted into its cells.
135
How do scientists use genetic engineering?
1: bacteria have been genetically modified to produce human insulin that can be used to treat diabetes
2: genetically modiefied crops had their genes modified to improve size and quality of fruit or make them resitant to disease insects and herbicides
3: sheep have been genetically engineered to produce substances like drugs in their milk that can be used to treat human diseases
4: Scientists are reasearching genetic modification treatments for inherited disease cause by faulty genes
eg: inserting working genes into people with disease (gene therapy)
136
Cons of GM Crops,
1: affect number of wild flowers and population of insects that live in and around crops reducing farm biodiversity.
2: not safe, concerend that not fullt understand effects of eating them on humans. Worried people may develop allergies from fruit
3: transplanted genes may get out in natural environment.
ex: herbicide resistant gene picked up by weeds creating superweed variety.
137
pros of GM crops.
1: increase yield and means more food
2: developing nations lack nutrients in diet, GM crops could be engineered to contain nutrients missing ex: golden rice, has beta carotene lack of this causes blindness.
3: they are already been grown in some places with no problems
138
How plants can be cloned by tissue cultures
1: few plant cells are put in a growth medium with hormones and grow into new plants -clones of the parent plant
2: plants made very quickly in little space and can be grown all year
3: used by scientists to preseve rare plants that are hard to reproduce naturally and by plant nurseries to produce stock
139
how plants can be cloned by cuttings
gardners take cuttings from good parents plant and then plant them to producegenetically idnetical coopies of the parent plant.
2:plants can be produced quickly and chaeply older simpler method than tissue culture
140
How to make animal clones using embryo transplants?
sperm cells from prize bull and egg cells from cow.
sperm then used to artificially fertilise an egg cell.
the embryo that develops splits many times to form clons before any cell is specialised.
cloned embryos then implanted into lots of other cows where they grow into baby cows
hundreds of ideal offspring produced each year from best bull/cow
141
How adul cells make clones?
take an unfertilised egg and remove nucleus
the nuclesu then removed from an adult body cell is inserted into the empty egg cell.
egg cell stiumated by electric shock so it divides like normal embryo
when embryo is ball of cells its implanted into womb in adult female
grows into a gentically identical copy of original adult body cell as it has smae genetic info.
-this created dolly the famous cloned sheep.
142
Issues with cloning
- reduced gene pool
- fewer different alleles in population
- if popualtion all closely related disease could wipe them out as no allele has resitance
- cloned animals arent healhty as normal ones eg:dolly had arthiritis which tends to occur in old sheep
- worry humans are cloned in future and some children may be born disabled
143
pro of cloning
- study of animal clones lead to greater understanding of development of embryo and age realted disorders
- preserve endangered species
144
What are fossils?
Remains of organisms from many thousands of years ago which are found in rocks. they tell us about how much or how little organisms have changed over time.
145
How fossils form in rocks through gradual replacement by minerals.
teeth, shells, bones which don't decay easily last a long time when buried.
MOST FOSSILS
Theyr'e eventually replaced by minerals as they decay forming rock like substance shaped like original hard part
Surrounding sediments also turn to rock but fossil stays distinct inside the rock and eventually someone digs it up
146
How fossils are formed from casts and impressions?
fossils are formed when an organism is buried in a soft material like clay.
the clay hardens around it and organism decays leaving a cast itself.
animals burrow or a plants root can be preserved by casts
footprints can also be pressed into these materials when soft leaving an impression when it hardens
147
How fossils form through preservation in places where no decay happens?
in amber (clear yellow stone made from fossilsied resin) and tar pits theres no oxygen or moisture so decay microbes wont survive
in glaciers its too cold dor decay microbes to work
peat bogs too acidic for decay microbes
(Pete marsh found in a bog)
148
Where did first living thing come from?
various hypotheses but no-one knows
-maybe in primordial swamp or under sea
maybe simple organic molecules brought on earth by comets
149
Why can these ideas about the first living things be disproved?
Lack of valid evidence
early forms were soft bodied and it decayed completley so no fossils
may have destoryed by geological activity ie:tectonic plates may have crushed fossils already in formed rock
150
what is a species?
group of similiar organism that can reproduce to give fertile offspring
151
what is speciation?
development of new species,occurs when populations of the same species become so different they can no longer sucessfully interbreed to produce fertile offspring.
152
what is isolation?
populations of a specie are seperated
153
What causes isolation?
physical barrier. eg:floods and earthquakes can cause barriers that geographically isolate some individuals from the main population.
154
What are conditions like in physical barrier?
have different climates as the enviromnet is different on each side, different characteristics will become more common in each population due to natural selection operating differently on the populations.
155
in speication what does each population show?
genetic variation as they have a wide range of alleles
in each population individuals with characteristics that make them better adapted to their environment have a better chance of survival and so are more likely to breed succesfully.
so alleles that control the beneficial features are more likely to be passed on to next generation
eventually individuals from the different populations will have changed so much they wont be able to breed with one another to produce fertile offspring
the two groups will have become seperate species
156
Who was alfred russel wallace?
scientist working at same time as darwin
early scientist working on idea of speciation
observation heloed us understand speciation today
curent understanding developed by more evidence over time
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What did wallace do?
came up with the idea of natural selection
published work on subject together with darwin in 1858
then prompted darwin ot publish on the origin of species in 1859
158
Waht observations did wallace make?
gave evidence to support theory of evolution by natural selection
realsied warning colours used by butterflys to deter predators from eating them and this was a beenficial characteristic which evolved by natural selecion
159
What can some bacteria develop in their DNA?
random mutations
lead to changes in the bacterias characteristics so they are less affected by a particular antibiotic this can lead to antibiotic resistant strains forming as the gene for antibiotic resistance becomes more common in the population.
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Why is bacteria having a random mutation a huge problem??
they are rapid at reproducing and can evolve quickly.
161
For the bacterium what was the advantage of being antibiotic resistant?
ability to resist antibiotics is a big advantage
better able to survive even in host who is being treated to get rid of infection so it lives longer and reproduces which increases population size and antibiotic resistance strain.
162
Why are anit biotic resistant strains a problem for people?
they arent immune to the new strain so no effective treatment
so the infection easily spreads between people, sometimes drug companies come up with new antibiotics but superdrugs are resistant to most antibiotics
163
What is MRSA?
Common superbug that really hard to get rid of.
| affects people in hospitals and can be fatal if enter their bloodstream.
164
how is the problem of anti biotic resistance getting worse?
overuse and innapropriate use of antibiotics as doctor overprescribe for non serious conditions or infections caused by virus.-antibiotics dont cause resitance they create situation when naturally resistant bacteria have an advantage so increase number
- not taking the full course so not all bacteria is destroyed which means some are left to mutate and develop into antibiotic resistant strains
- farming antibiotics can be given to animals to prevent them becoming ill and to make them grow faster. lead to the development of antibiotic resitant bacteria in animals which can spread to humans during ocnsumption increase concern about overuse in agriculure leads to a ban
165
what has increase of antibiotic resistance encouraged?
drug companies to develop new antibiotics that are effective against resistant strains
unfortuanlty rate of developemnt is slow so we are unlikely to be able to keep up with demand for new drugs as more antibiotic resitant strains develop and spread and its super costly.
166
traditionally what were organisms classified as?
system proposed in 1700s by carl linnaeus, which grouped living thing according to characteristics and structures that make them up
living things are first divided in kingdoms eg plant
then kingdoms are subdivided into smaller groups
167
what are linnaeus groups called?
```
kingdom
phylum
class
order
family
genus
species
```
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Why did scientist put forward a new classification model?
knowledge of biochemical processes taking place in organisms and miscroscopes developed it allowed us to find more about internal structure
169
who proposed the three domain system in 1990
carl woese,
he used evidence gathered from new chemical analysis techniques such as rna sequence analysis he found in some cases species thought to be closely related in traditional classification systems arent closely related.
170
what was three domain system part called archaea
organisms in this domain were once thought to be primitive bacteria but theyre actually a different type of prokaryotic cell. they were first found in extreeme places such as hot springs and salt lakes.
171
three domain system what is bacteria?
this domain contains true bacteria like e coli and staphylococcus although they often look similar to archaea there are lots of biochemical differences between them.
172
3 domain system eukaryota
domain includes a broad range of organisms including fingi plants and animals and protists
173
what happen after 3 domain system
then subdivided into smaller groups mad eby linnaeus
174
what is the binomial system?
every organism is given its own 2 part latin name
175
first part of binomial system
genus that the organism belongs to
| give info about anscestory
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second part of binomial system
refers to species
| eg: humans known as homo genus and sapiens is the species
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why is the binomial system used?
used worldwide so scientists in different countries or who speak different languages all refer to particula species by same name avoid confusion.
178
What do evolutionary trees show?
how scientists think different species are related to each other
they hsow comon anscestors and relationships between species
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on a evolutionary tree what does a recent common ancestor show?
more closely related the two species are and the more characteristics thye are likely to share.
180
How do scientists work out evolutionary relationships?
they analyse lots of different types of data
for living organisms they use current classification data
for extinct species they use info from fossil records.
