Biology Flashcards
(94 cards)
1
Q
Unit 2 - Cells & Control
A
- Cell Division
- Stem cells
- Brain and Eye function
- The nervous system
2
Q
What is mitosis and what is it used for?
A
- Mitosis is the the stage of the cell cycle when the cell divides.
- Is used for cell growth or repair
- Is used in asexual reproduction in some organisms
3
Q
What are the stages of the cell cycle that are part of mitosis?
A
Prophase –> Metaphase –> Anaphase –> Telophase
4
Q
What happens during cytokinesis?
A
The cytoplasm and cell membrane divide to form two separate cells.
5
Q
A normal human body cell contains 23 pairs of chromosomes.
How many would be in each new human cell formed by mitosis?
A
Each cell will have 46 chromosomes (23 pairs).
6
Q
Name the two methods plants use to grow.
A
- Cell division
- Cell elongation
7
Q
Why is cell differentiation important and how does it differ between plants and animals?
A
- Cell differentiation allows for cells to become specialised for a specific function, which allows multicellular organisms to work more efficiently.
- The ability to differentiate is lost in most animal cells as the organism ages but plant cells never lose this ability.
8
Q
What are growth charts used for?
A
- To assess a child’s growth overtime, so any problems can be highlighted.
9
Q
Describe how cancer can develop from changes in a cell?
A
If there is a change in any of the genes that control cell division, the cell may start dividing uncontrollably. This can result in a mass of abnormal cells called a tumour which can develop into cancer if it invades and destroys surrounding cells.
9
Q
Describe how cancer can develop from changes in a cell?
A
If there is a change in any of the genes that control cell division, the cell may start dividing uncontrollably. This can result in a mass of abnormal cells called a tumour which can develop into cancer if it invades and destroys surrounding cells.
10
Q
What is an embryonic stem cell?
A
An undifferentiated cell found in early human beings which has the potential to divide and produce any kind of cell at all.
11
Q
Where can stem cells be found in:
a.) Adult humans
b.) Plants
What do they do?
A
a. ) Bone marrow - used to replace damaged cells such as blood or skin cells
b. ) Meristem tissue - where growth occurs
12
Q
Describe two potential risks of using stem cells in medicine.
A
- If donor stem cells are contaminated w/ a virus, the virus could be passed onto the recipient.
- If cells divide too quickly inside a patient, a tumour may develop.
- If transplanted cells aren’t grown w/ the patient’s own stem cells, their body might reject them.
13
Q
Describe one example of how adult stem cells can be used to cure a disease.
A
e.g Sickle cell anaemia can sometimes be cured w/ a bone marrow transplant. The bone marrow contains adult stem cells which produce new healthy blood cells.
14
Q
Suggest how embryonic stem cells could potentially be used to treat a patient after a heart attack.
A
- Embryonic stem cells could be made to develop into heart muscle cells.
- These could repair the damaged tissue or replace the damaged cells after a heart attack.
15
Q
What is the cerebellum responsible for?
A
- Muscle coordination
- Balance
16
Q
What does the medulla oblongata control?
A
Unconscious activities, e.g breathing and heart rate.
17
Q
Describe the structure and function of the cerebral hemispheres.
A
- The cerebral hemispheres are the two halves of the cerebellum.
- The right hemisphere controls the muscles on the left side of the body and vice versa.
- Different parts are responsible for different things, including movement, intelligence, language, memory and vision.
18
Q
Describe how a PET scanner can be used to study Alzheimer’s.
A
- PET scanners use radioactive materials to show which parts of the brain are active when the person is inside the scanner.
- Scans can be used to show if areas of the brain are unusually inactive or active when compared to the activity of a normal brain.
19
Q
Why is it hard to repair damage to the nervous system?
A
Neurones in the CNS don’t readily prepare themselves and scientists haven’t yet developed a way to repair nervous tissue in the CNS.
20
Q
A doctor is assessing whether to remove a brain tumour from a patient. Suggest two possible problems w/ this brain treatment.
A
E.g
- The tumour might be growing in a part of the brain that cannot be reached via surgery.
- Brain surgery could result in permanent damage to the brain.
21
Q
True or False?
Muscles and glands are examples of receptors.
A
False.
They are effectors.
22
Q
In humans, what does the CNS (central nervous system) consist of?
A
The brain and spinal cord.
23
Q
Which type of neurone carries impulses from the CNS to effectors?
A
Motor neurone.
24
What is the benefit of an axon having a myelin sheath?
A myelin sheath acts as an electrical insulator, which speeds up the movement of electrical impulses along the axons.
25
Describe the difference in function between dendrons and axons.
Dendrons carry nerve impulses towards the cell body, whereas axons carry nerve impulses away from the cell body.
26
Compare the difference in structure of a sensory and a motor neurone.
Sensory neurones have one long dendron and one short axon, whereas motor neurones have many short dendrites and one long axon.
27
Describe the structure and function of a relay neurone.
A relay neurone has:
- Many short dendrite that carry nerve impulses from sensory neurones to the cell body.
- An axon that carries nerve impulses from the cell body to motor neurones.
28
What is a synapse?
A synapse is the connection between two neurones.
29
How are nerve signals transferred across a synapse?
Neurotransmitters (chemicals) diffuse across the synapse and set off a new electrical impulse in the next neurone.
30
Reflexes do not involve conscious parts of the brain.
| Why is this advantageous?
It reduces the chance of an injury, as it means that reflexes can be rapid and automatic.
31
If someone is stung by a nettle, a reflex action causes them to immediately move their hand away from it.
In this reflex action, what is:
a.) The stimulus
b.) The effector
a. ) The nettle.
| b. ) The muscles in their hand.
32
Describe the pathway taken by the aforementioned reflex from the nettle stimulus to the response.
- The nettle sting (stimulus) is detected by pain receptors in the hand. These send impulses along a sensory neurone to a relay neurone in the CNS.
- The impulse is then transmitted between the relay neurone and motor neurone
- Impulses travel along the motor neurone to the hand muscles (effector), which contract to move the hand away.
33
True or False?
| People w/ long sightedness are unable to focus on distant objects.
False. People w/ long sightedness are unable to focus on near objects.
34
Give three defects of the eye that can cause vision problems.
- Long sightedness or short sightedness.
- Colour blindness.
- Cataracts.
35
```
How do the:
a.) Iris
b.) Cornea
c.) Lens
enable us to view objects?
```
a. ) The iris controls the amount of light entering the pupil.
b. ) The cornea refracts light into the eye.
c. ) The lens also refracts light, focusing it onto the retina.
36
The retina is covered in receptor cells. Describe the differences between the two types of receptor cells (rods and cones) found there.
- Rods are more sensitive in dim light but can't sense colour.
- Cones are sensitive to different colours but not as good in dim light.
37
What is a cataract and how can it be treated?
- A cataract is a cloudy patch on the lens. This stops light from being able to enter the eye normally.
- It can be treated by replacing the faulty lens w/ an artificial one.
38
A man is sitting in a park reading a book. He looks up across the park at a dog. The dog looks blurry.
Describe the eye defect that the man has and how it could be corrected.
- The man is short-sighted. His lens may be misshapen and bend light too much or his eye could be too long. This means the light from distant objects is brought into focus in front of the retina.
- Glasses or contact lenses w/ a concave lens could correct this.
39
Unit 3 - Genetics
- Sexual and asexual reproduction
- DNA
- Protein synthesis
- Variation and Inheritance
40
What type of reproduction do humans use to produce offspring?
Sexual reproduction (two parents).
41
True or False?
| A zygote is haploid.
False. A zygote is formed when a male gamete fuses w/ a female gamete and ends up w/ a full set of chromosomes, therefore is diploid.
42
Name the type of cells that are formed when a cell divides by meiosis.
How many are formed when a cell undergoes meiosis?
- Gametes are formed by meiosis.
| - Four gametes are produced each time a cell divides this way.
43
A mouse body cell contains 40 chromosomes. How many chromosomes will be in the mouse cells produced by meiosis?
There will be 20 chromosomes in each cell (gamete) after meiosis.
44
Cats reproduce via sexual reproduction.
| What happens at the cellular level during sexual reproduction in cats?
- A male and a female cat each produce gametes by meiosis. These contain half the number of chromosomes of a normal cell.
- An egg from the female cat fuses w/ a sperm from the male cat, forming a zygote w/ the full number of chromosomes.
45
Which type of reproduction:
a. ) is faster
b. ) requires more energy
a. ) Asexual reproduction
| b. ) Sexual reproduction
46
How are offspring produced using asexual reproduction?
In asexual reproduction, a cell divides by mitosis, resulting in two diploid daughter cells.
47
What advantages do asexually-reproducing species have over sexually-reproducing species?
- Asexual reproduction only needs one parent, so organisms can reproduce whenever conditions are favourable, w/out a mate.
- Lots of offspring are produced, allowing organisms to populate new areas rapidly.
48
If conditions in an environment change, which types of species (in terms of asexually/sexually reproducing) are more likely to survive and why?
- Sexually-reproducing species are more likely to survive as there is greater genetic variation than there is in an asexually-reproducing species.
- This means that the sexually-reproducing species are more likely to have individuals w/ characteristics that will help them survive in the changed environment and reproduce.
49
What are the 4 different bases in DNA?
- A (Adenine)
- T (Thymine)
- C (Cytosine)
- G (Guanine)
50
What is bigger - a gene or a genome?
Genome.
(A genome is the entire section of DNA in an organism and a gene is a section of a DNA molecule coding for a specific protein)
51
How many strands make up a section of DNA and what shape do they form?
- DNA is made up of two polymer strands.
| - These strands form a double helix.
52
Which bases pair together and what are they held with?
- A pairs w/ T.
- C pairs w/ G.
- They are held together w/ weak hydrogen bonds.
53
Describe the structure of a nucleotide.
A nucleotide consists of a sugar, a phosphate group and one of the four different bases (which is attached to the sugar).
54
What method could be used to extract DNA from fruit?
- Mash the fruit and put this in a solution of detergent and salt. Mix this together.
- Filter the mixture to get the froth and larger, insoluble bits of cell out.
- Gently add ice-cold ethanol to the filtrate.
- Scrape out the stringy, white precipitate (the DNA) w/ a glass rod.
55
What is a mutation?
A rare, random change in an organism's DNA base sequence.
56
What is meant by a genetic variant?
A different version of a gene, caused by a mutation within the gene.
57
A section of protein contains 25 amino acids. Calculate the number of bases in the gene which coded for this amino acid sequence.
75 bases.
One amino acid is coded for by three bases.
3 x 25 = 75
58
Explain how the order of bases in DNA affects the shape of enzymes.
Each protein, such as enzymes, has its own particular number and order of amino acids. This is determined by the order of bases in the gene that codes for it. The resulting amino acid chains fold up to give the enzyme a different, specific shape.
59
Which stage of protein synthesis involves RNA polymerase?
Transcription.
60
The ALB gene codes for serum albumin. How is this code transferred to a ribosome?
- RNA polymerase binds to the region of non-coding DNA in front of the ALB gene.
- The DNA strands unzip and and the RNA polymerase moves along one of the strands of the DNA.
- It uses the coding DNA in the gene as a template to make a strand out of mRNA that is complimentary to the gene.
- The mRNA molecule then moves out of the nucleus and joins w/ a ribosome.
61
How does tRNA help the production of serum albumin once the code is at the ribosome?
- tRNA molecules bring specific amino acids to the ribosome in the order that matches the base codons in the mRNA.
- The amino acids can then be joined together by the ribosome to form serum albumin.
62
If someone has a mutation in the non-coding DNA in front of the ALB gene, how could this affect the quantity of serum albumin produced?
- Mutations in the non-coding DNA in front of a gene can affect the ability of RNA polymerase to bind to it.
- How well the RNA polymerase can bind to this region affects how much mRNA is transcribed and therefore how much serum albumin is produced
63
Mendel carried out experiments w/ pea plants of different heights.
Describe one of these experiments.
- Mendel crossed one tall plant w/ a dwarf plant and found that the offspring were all tall plants.
- He then bred two of the tall offspring together and found that three tall offspring were produced for every one dwarf offspring overall.
64
In one of his experiments, Mendel produced a 3 : 1 ratio of tall : dwarf plants.
If there were 20 plants produced, how many were dwarf?
5 dwarf plants.
- Total no. of plants is 20.
- Divide by 4 parts in the ratio 3 : 1.
- 20 ÷ 4 = 5 so, total no. of dwarf plants is 5
65
Give three conclusions that Mendel reached from his work.
- Characteristics in plants are determined by 'hereditary units'.
- Hereditary units are passed onto offspring unchanged from both parents.
- Hereditary units can be dominant or recessive.
66
Why didn't other scientists of Mendel's time recognise the importance of his work?
There wasn't enough background knowledge to properly understand Mendel's findings as, at the time, scientists didn't know about genes, DNA and chromosomes.
67
What does homozygous mean?
Homozygous means you have two alleles for a particular gene are the same.
68
What alleles must you have to display a recessive characteristic?
- You must have two recessive alleles for a particular gene. In other words, you must be homozygous recessive.
69
Describe the difference between genotype and phenotype.
- Genotype is the combination of alleles you have.
| - Phenotype, however, is the characteristics that you have (which is determined by the alleles).
70
The alleles F and f are responsible for determining whether a person has cystic fibrosis.
What is the probability of a child having cystic fibrosis if both parents have the genotype Ff?
25% or 1 in 4 probability.
| Child must have the ff genotype in order to inherit this
71
How many X chromosomes do men carry?
One.
| Men have one X chromosome and one Y chromosome.
72
What does it mean if a characteristic is 'sex-linked'?
The allele that codes for a characteristic is located on a sex chromosome (X or Y).
73
What are codominant alleles?
- Alleles that aren't dominant over each other
| - They are equally dominant, so they are both expressed in the phenotype.
74
How many alleles does the gene for blood type in humans have?
It has three different alleles:
- IA
- IB
- i
75
Give the possible genotypes of someone w/ blood group B.
- IB IB
| - IB i
76
Is variation in eye colour in humans due to genetic or environmental variation?
Variation in eye colour is due to genetic variation.
77
How do mutations introduce genetic variation into populations?
- Mutations change the sequence of bases in DNA.
| - This can result in an allele when they occur in a gene.
78
Describe how sexual reproduction causes genetic variation.
Sexual reproduction results in alleles being combined in lots of different ways in offspring.
79
When a mutation occurs, what is the most common outcome for the phenotype?
- Most mutations are neutral - they have no effect on phenotype.
- Very rarely will a mutation have a big effect on a phenotype.
80
In a field of sunflowers, there is variation in plant height.
Explain why you would expect to see this variation and what might cause it.
- There is usually extensive genetic variation w/in a population of a species, mostly caused by mutations.
- This affects how tall each plant will grow.
- There will also be variation caused by environmental factors,
e. g how much sunlight each plant gets.
81
What did the Human Genome Project aim to do?
The Human Genome Project aimed to find every single human gene in order to make a complete map of the human genome.
82
Describe how the Human Genome Project can help improve testing for inherited disorders, such as cystic fibrosis.
- Scientists are now better able to identify the genes and alleles that are suspected of causing an inherited disorder.
- Once the allele that causes an inherited disorder has been identified, people can be tested for it.
83
Genome research has found that there are some common genetic variations in people.
Suggest how this knowledge can be used to tailor treatments to specific people.
- Scientists can use this knowledge to design new drugs that are specifically tailored to people w/ a particular genetic variation.
- They can also determine how well an existing drug will work for an individual.
84
The Human Genome Project may allow doctors to know what genes predispose people to certain diseases.
Give one advantage and one disadvantage of this knowledge.
E.g
Advantage:
- It would enable people to get individually tailored advice on the best diet and lifestyle to avoid their likely health problems.
Disadvantage:
- It might allow employers to discriminate against people who are genetically likely to get a disease.
85
Unit 4: Natural Selection & Genetic Modification
- Natural selection & evolution
- Selective breeding
- GMOs & clones
86
Give two selection pressures that could affect an individual's chance of survival.
E.g
- Predation
- Competition for resources (e.g food, water, mates etc)
- Disease
87
Why can bacteria evolve rapidly?
Bacteria reproduce at a fast rate.
88
What is meant by 'natural selection'?
- Individuals w/ characteristics that make them better adapted to their environment have a better chance of surviving and reproducing successfully.
- This means that the alleles that are responsible for the useful characteristics are more likely to be passed on to the next generation.
89
A population of lizards live in a desert and are preyed on by eagles.
Some lizards are brown and more difficult to see. Others are bright pink and stand out against the sand.
Which characteristic is likely to become to more common? Explain.
- The brown colour is likely to become more common in the population due to natural selection.
- The brown lizards are better adapted due to them being harder for the eagles to spot.
- More brown lizards will survive and breed and pass the allele for their brown colour to the next generation.
89
A population of lizards live in a desert and are preyed on by eagles.
Some lizards are brown and more difficult to see. Others are bright pink and stand out against the sand.
Which characteristic is likely to become to more common? Explain.
- The brown colour is likely to become more common in the population due to natural selection.
- The brown lizards are better adapted due to them being harder for the eagles to spot.
- More brown lizards will survive and breed and pass the allele for their brown colour to the next generation.
90
Describe how a population of bacteria can become resistant to a particular antibiotic.
- Bacteria can develop random mutations in their DNA that make them resistant to a particular antibiotic.
- Antibiotic-resistant bacteria are more likely to survive and reproduce, passing on the gene for resistance.
- The gene for resistance becomes more common in the population due to natural selection.
91
Explain how Darwin and Wallace's ideas about evolution have influenced how living organisms are classified by biologists today.
- Darwin and Wallace's ideas about evolution have led to the understanding that all living organisms have descended from a common ancestor and therefore must be related in some way.
- Based on this idea, biologists now classify organisms based on how closely related they are.
92
Other than changing the way that biologists now classify organisms, give two ways that Darwin and Wallace's ideas have had an impact on modern biology.
- We now understand the importance of completing a course of antibiotics to prevent resistant bacteria spreading, and the need to constantly develop new antibiotics to fight newly evolved bacteria.
- We also now understand the importance of genetic diversity and how it helps populations adapt to changing environments, which has led to conservation projects to help protect species.
