6- Inheritance, variation and evolution (2) Flashcards
1
Q
What are chromosomes?
A
long strands of DNA
2
Q
What are genes?
A
small section of DNA that codes for a sequence of amino acids which make a specific protein
3
Q
What is the structure of DNA like?
A
- sugar-phosphate back bone
- base that joins to complimentary base
- double helix structure
- polymers made up of repeating nucleotides
4
Q
What are mutations?
A
- Changes to genetic codes
- change sequence of DNA bases to produce a genetic variant
5
Q
Describe sexual reproduction.
A
- mother and father produce gametes by meiosis
- egg and sperm each have 23 chromosomes, fuse to make 46
- genetic information from mother and a father
- produces genetically different cells
6
Q
Describe asexual reproduction.
A
- only one parent
- offspring are genetically identical to parent - clone
- ordinary cell makes a new cell by dividing
- bacteria, some plants and some animals reproduce asexually
7
Q
Explain the process of meiosis.
A
- genetic information duplicated
- chromosomes arranged into pairs
- chromosome pairs line up in centre of the cell
- pairs pulled apart so each new cell only has one copy of each chromosome
- in the second division chromosomes line up again in centre of cell and arms of chromosomes pulled apart
- four gametes produced, single set of each chromosome in it, each genetically different from the other
8
Q
What are the advantages of sexual reproduction over asexual reproduction?
A
- sexual produces variation
- variation increases species chance of survival
- better adapted to environment
- selective breeding for desired characteristics and increased food production
9
Q
What are the advantages of asexual reproduction?
A
- only needs one parent
- less energy - don’t have to find a mate
- faster
- offspring can be produced in favourable conditions
10
Q
What organisms use both methods of reproduction and how?
A
- malaria - reproduces sexually in the mosquito and asexually in the human host
- strawberries produce seeds sexually and runners asexually
11
Q
What did Mendel do?
A
- genetic experiments on pea plants
- concluded characteristics are determined by ‘hereditary units’
- hereditary unitspassed on to offspring unchanged from both parents, one unit from each parent
- wasn’t until after death people realised significance of his work
-research massively helped understanding
12
Q
Describe genetic variation.
A
- caused by different genes
- because characteristics are determined by genes inherited from parents
- genes passed on in sex cells (gametes)
- genes are combination of those from parents so never identical
13
Q
Describe environemntal variation
A
- characteristcs in an environment causing visible changes to a species
- e.g weight is determined by environmental conditions rather than genetic
14
Q
What was Darwin’s theory of evolution?
A
- it was done by natural selection
- had to compete for limited resources in an ecosystem
- more suitable characteristics means more likely to survive - animals that survive reproduce and pass favourable genes to offspring
- organisms less adapted less likely to reproduce and carry on favourable characteristics
- beneficial characteristics become more common and species changes - evolves
15
Q
What is speciation?
A
- the development of an organism so much that a new species is formed
- happens when populations of the same species can no longer interbreed
16
Q
What is extinction?
A
- no individuals of a species remain
- caused by environment changes, new predators, new diseases, catastrophic event
17
Q
Why didn’t people Darwin’s theory of evolution?
A
- went against common religious beliefs
- Darwin couldn’t explain how these new characterists appeared or were passed on
- didn’t know anything about gene’s or mutations
- wasn’t enough evidence to convince other scientists
18
Q
What were Lamarck’s idea’s on evolution?
A
- argued changes organism acquires during lifetime passed on - e.g if characteristic used a lot the offspring would inherit it
19
Q
What is selective breeding?
A
- selecting an organism with the most favourable characteristic to produce the most favourable offspring - e.g disease resistant crops
20
Q
What are the drawback’s of selective breeding?
A
- reduced gene pool and variation
- can cause health problem’s and disease
- hard to survive if new disease introduced as less chance of resistant alleles
21
Q
What is genetic engineering?
A
- transfering genes responsible for more favourable characteristics from one organism to another so it also has desirable characteristics
- usefulgene isolated from one organisms genome using genome’s and is inserted into a vector
- vector usually virus or bacterial plasmid
- when vector introduced to target organism, useful gene inserted
- used for genetically modifying crops and making animals resistant to disease
- -
22
Q
- Why is genetic engineering contraversial?
A
-worries about long term effects for future generations
23
Q
What are the adavantages of Gm CROPS?
A
- Increase yield
- add missing nutrients
- already being grown in placed and not caused problems
24
Q
What are the disadvantages of GM crops?
A
- some people believe will affect number of wild flowers growing and reduce biodiversity
- not everyone convinced it’s safe as we don’t fully understand effects on human health
25
Q
How can plants be cloned by tissue culture?
A
- few plant cells put in growth medium with hormones and grow into clones of parent plant
- plants can be grown very quickly in little space and grown all year round
- can be used to preserve plants that are rare and hard to produce naturally
26
Q
How are plant clones produce by cuttings?
A
- gardeners take cuttings from parent plants to produce genetically identical clones
- can be produced quickly and cheaply
- more simple method than tissue culturing
27
Q
How can you make animal clones with embryo transplants?
A
- sperm cells taken from a prize bull and egg cells from a prize cow using embryo transplants
- sperm used to artificially fertilise egg
- embryo developed and split multiple times
- cloned embryo’s implanted into lots of other cows where they grow into baby calves
- hundreds of ideal offspring can be produced every year
28
Q
How is adult cell cloning used to make clones?
A
- unfertilised egg, nucleus removed and inserted into ‘empty egg cell
- egg cell stimulated by electric shock to divide
- implanted into woman womb with genetically identical copy of original adult body cells
29
Q
What are the issues surrounding cloning?
A
- reduced gene pool - less variation
- might not be as healthy as normal animal
- people worry humans might be cloned
30
Q
How are most fossils made?
A
- reptile dies and falls to the ground
- flesh rots, leaving skeletons to be covered in sand or soil and clay
- skeleton protected by sand or soil for millions of years
- skeleton becomes mineralised and turns to rock
- eventually, fossil emerges as rocks move and erosion takes place
31
Q
How can casts and impresion fossils be made?
A
- when an organism burried in soft material clay
- clay hardens and organism decays, leaving a cast of itself - footprints can also be preserved as casts
32
Q
How can preservation take place in other forms?
A
- in amber and tar pits - no oxygen or moisture so decay microbials cannot survive
- in glaciers where it’s too cold for decay microbes to work - Peat bogs are too acidic for decay microbials
33
Q
How can Isolation cause speciation?
A
- populations of a species seperated
- conditions on either side of barrier slightly different e.g different climates
- populations adapt to new climates
- pass on favourable adaptations to offspring
- new species is formed
34
Q
What is antibiotic resistant bacteria?
A
- random mutations that cause bacteria’s characteristics to change e.g more resistant to antibiotic, causing it to become unaffected by antibiotics
- bacteria reproduce rapidly so adaptations happen quickly - resistant bacteria reproduce and increase population size - MRSA antibiotic superbug that affects people in hospitals and can be fatal
35
Q
What is the Linnaean system 1700’s?
A
- system in organising animals introduced by Carl Linnaeus - divided into Kingdom, Phylum, Class, Order, Family, Genus, Species
36
Q
What is the Woese system?
A
- 3 domain system
- Archaea - prokaryotic cells first found in hot springs and salt lakes
- Bacteria - true bacteria e.g E.Coli
- Eukaryota - wide range of organisms including fungi, plants, animals and protists
- these are then subdivided into Linnaeus sytem
37
Q
What is the binomial system?
A
- how organisms are named
- first part is genus, second part is species
- used worldwide, same in all countries
