Biology Flashcards
(128 cards)
0
Q
What are the parts of a plant cell?
8
A
Nucleus
Cell membrane
Cytoplasm
Ribosomes
Mitochondria
AND
Cell wall
Vacuole
Chloroplasts
1
Q
What are the parts of an animal cell?
5
A
Nucleus Cell membrane Cytoplasm Ribosomes Mitochondria
2
Q
What’s the purpose of a nucleus?
A
To control the cell’s activities.
3
Q
What’s the purpose of a cell membrane?
A
To control the passage of substances in and out of the cell.
4
Q
What’s the purpose of cytoplasm?
A
It’s where chemical reactions take place.
5
Q
What’s the purpose of ribosomes?
A
It’s where protein synthesis occurs (where proteins are made).
6
Q
What’s the purpose of mitochondria?
A
It’s where energy is released during aerobic respiration.
7
Q
What’s the purpose of a cell wall?
A
It keeps the plant rigid and supported.
8
Q
What’s the purpose of chloroplasts?
A
They contain chlorophyll which so needed for photosynthesis.
9
Q
What’s the purpose of a vacuole?
A
It’s filled with cell sap / water which is there all the time.
10
Q
What is bacteria?
A
Very small, single celled organisms which are only a few micrometers. They don’t have a nucleus, mitochondria, chloroplast or vacuole.
Their DNA is found in the cytoplasm and controls the cell’s activities.
It has a flagellum (which looks like a tail).
They contain plasmids which helps them replicate.
They also have a slime capsule.
11
Q
What’s yeast?
A
Single celled organisms
They have a nucleus
They reproduce by budding which is asexual an involves new cells forming from existing cells.
They have mitochondria but not chloroplasts.
12
Q
What’s a specialised cell?
A
A cell with a specific job to do e.g. Root hair cells (increase surface area), sperm cell (the tail), neurons carry impulses from the receptors to the CNS.
Plant cells with many chloroplasts will be photosynthesising.
13
Q
What is diffusion?
A
The spreading out / moving of (liquid or gas) particles from areas where the substance is concentrated to a less concentrated area (until it is evenly spaced out).
14
Q
Where does diffusion occur in the body and plants?
A
The diffusion of oxygen into the cells of the body from the bloodstream as the cells are respiring (using up oxygen).
Glucose and nutrients in the intestine
CO2 in plants
15
Q
What determines the net movement of particles across a cell membrane?
A
The concentration on either side of the membrane.
16
Q
What’s a tissue?
A
A group of cells with similar structure and function.
17
Q
What are the types of animal tissue?
A
Muscle - brings about movement
Glandular - produce substances like enzymes or hormones
Epithelial - covers the body
18
Q
What are the types of plant tissue?
A
Epidermal - covers plant
Mesophyll - photosynthesise
Xylem and phloem - carry substances
19
Q
What’s an organ?
A
An organ is made up of several types of tissues
E.g. The stomach is made up of muscular tissue (to churn food), glandular tissue (produce digestive juices) and epithelial (cover the stomach).
(The leaf, stem and root are plant organs which contain epidermal tissue, mesophyll tissue and xylem and phloem.)
20
Q
What’s an organ system?
A
A group of organs which perform similar functions.
E.g. The digestive system is adapted to exchange substances with the environment. Insoluble molecules must be changed into soluble molecules.
The digestive system is a muscular tube including - glands (pancreas and salivary), stomach, small intestine, (liver bile) and large intestine.
(Duodenum is the first part of the small intestine directly beneath the stomach).
21
Q
What’s photosynthesis?
A
When light energy is transferred into chemical energy.
22
Q
What’s the equation for photosynthesis?
A
Carbon dioxide + water -> glucose + oxygen
6CO2 + 6H2O -> C6H12O6 + 6O2
23
Q
How does photosynthesis occur?
A
It can only be carried out by green plants.
Chlorophyll in the chloroplasts absorbs the sun’s light energy.
CO2 is taken in by the leaves and water by the roots.
Chlorophyll traps the light energy for photosynthesis.
The energy is used to convert CO2 and water into glucose (a sugar).
24
What are limiting factors for photosynthesis?
Limiting factors are anything which prevent the rate of photosynthesis from increasing.
The factors include:
Light
CO2
Temperature
25
How does temperature affect the rate of photosynthesis?
If it's cold, enzymes don't work effectively and will slow the rate however, if above a certain point (45c?) the enzymes will denature and stop working completely.
26
How do plants use glucose?
It's produced during photosynthesis which is then:
Converted into insoluble starch for storage
Used for respiration
Converted into fats and oils for storage
Used to produce cellulose which strengthens the cell walls
Used to produce proteins (and also need nitrate and mineral ions absorbed from the soil)
27
Name 3 substances used for storage in plants
Starch, fats and oils.
28
What physical factors affect the distribution of organisms?
```
Temperature
Nutrients
Light
Water
Oxygen
CO2
```
Farmers can also artificially control these factors.
29
How can you make sure an investigation is valid?
All possible variables must be controlled
Use a comparative investigation
Repeatable and reproducible measurements
The method used must answer the question
Appropriate sample size
30
What's the word equation for aerobic respiration?
Glucose + oxygen -> carbon dioxide + water (+ energy)
31
What are the levels of organisations?
```
Organelle
Cells
Tissues
Organ
Organ systems
Organisms
```
32
How do respiration and photosynthesis differ at night and day?
Respiration always occurs but photosynthesis is only during day.
(Bright day) - same O and CO2 given out as CO2 and O in.
(Dim light) - less but same O and CO2 given out as CO2 and O in.
(Dark) - only CO2 given off, no photosynthesis
33
How are leaves adapted for photosynthesis?
Thin- allows gasses to reach cells easily
Wide and flat - larger surface area
Veins - carry water to leaves and glucose back, support leaves
Stomata - allows gasses to move in and out
Spongey layer - gas exchange easier
Palisade layer - lots of chloroplasts
34
What's osmosis?
The diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane.
35
What's active transport?
When energy from respiration is used to move and uptake substances and particles against a concentration gradient.
36
How are villi in the stomach adapted?
| Same as alveoli in lungs
Thin walls
Lots of capillaries
Large surface area
37
What's transpiration?
Evaporation and diffusion of water.
38
What's aerobic respiration?
It's the release of energy from food when oxygen is available. (Oxygen and glucose)
Most of these reactions occur in the mitochondria.
Carbon dioxide and water are produced as waste products.
Respiration using oxygen.
Mitochondria are in all living things and is in every cell. Muscle tissue have lots of mitochondria since lots of energy is needed.
Photosynthesis and aerobic respiration are chemical opposites
39
How does our body use energy?
```
Working you muscles
Transporting chemicals
Absorbing food
Sending messages via nerves
Building cells
Maintaining body temperature
```
40
What's the equation for aerobic respiration?
Oxygen + glucose -> water + carbon dioxide [+ energy]
41
What happens to two flasks of peas, some boils and some germinating?
In the germinating flask, heat is produced as respiration is taking place so energy is released as heat.
The boiled flask had no temperature rise as respiration didn't take place.
42
What's the equation for anaerobic respiration?
Glucose -> lactic acid [+ energy]
It's respiration without oxygen
43
What's oxygen debt?
When we carry on vigorously breathing after exercise as the extra oxygen breaks down the lactic acid.
Amount of oxygen needed to get rid of the lactic acid.
44
What are proteins?
Proteins are made of long chains of amino acids e.g. Glycine.
The long chains are folded to produce specific shapes which depend on their functions.
The body makes most amino acids but essential amino acids which the body can't produce must be consumed.
Chemical reactions in cells are controlled by proteins called enzymes.
```
Proteins can be:
Catalysts (enzymes)
Antibodies
Hormones
Structural components of tissue
```
45
What are some uses of proteins?
Structural proteins - muscles
Messenger proteins - hormones
Immune system protons - antibodies
Biological catalysts - enzymes
(Each enzyme has a specific shape that only fits the substance e it catalysed.
The area where the enzyme and substrate fits is called the active site.
Breaks down - catabolic
Builds up - anabolic
46
What are the digestive enzymes and where are they found?
Mouth - amylase
Stomach - protease / pepsin
Pancreas - protease and carbohydrase
Small intestine - lipase and carbohydrase
Protease - breaks proteins into amino acids
Carbohydrase - breaks carbohydrates ""
Lipase - breaks fats into fatty acids and glycerol
47
How does temperature and pH affect enzymes?
Enzymes work at different pHs - too high or low for them will denature the enzymes.
Enzymes work slowly in lower temperatures and faster at body temperature but too high and the they will denature.
48
What are the uses of enzymes?
Biological washing powder contains enzymes to help clean clothes / digest food stains.
Protease and lipase - stain digesters in washing powder, best at low temps
Papin - whitening toothpaste digests stains on teeth
Protease - pre digest protein e.g. Baby food
Invertase (carbohydrase) - breaks down starch into glucose syrup and is used in soft centre chocolates.
Lactose - makes milk lactose-free
Isomerase - converts glucose syrup to fructose syrup. Because fructose syrup is sweeter than glucose despite having the same amount of calories, it is used to make sweeteners since you would use less of it so it has uses less calories.
49
What does it mean if an enzyme has been denatured?
Factors such as temperature or pH alter the shape of the active site and prevent the enzyme from working.
50
What's amylase?
A carbohydrase produced by the salivary glands, the pancreas and the small intestines.
It catalyses the digestion of starch into sugars in the mouth and small intestines.
51
What's protease?
It's produced by the stomach pancreas and small intestines.
| It catalyses the breakdown of proteins into amino acid in the stomach and small intestines.
52
What is lipase?
It's produced by the pancreas and small intestines. It catalyses the breakdown of lipids (fats and oils) to fatty acids and glycerol.
53
What is bile?
The liver produces bile that is stored in the gall bladder. The alkaline bile is squirted into the small intestine and neutralises the stomach acid.
Bile makes the conditions in the small intestines slightly alkaline.
Bile only neutralises acid, it does not contain enzymes.
This helps amylase and lipase since they work in the small intestine in slightly alkaline conditions.
54
What is a substrate?
The material or chemical on which an enzyme acts.
55
What is an active site?
The site on the enzyme where the reactants bind
56
What are enzymes?
Biological catalysts
They are large proteins and the shape of the enzyme is vital for its function. This shape has an area where other molecules can fit - the active site.
57
What do biological detergents contain?
Proteases and lipases that digest food stains.
| They work at lower temperatures than ordinary washing powders. This saves energy and money spent on electricity
58
What is isomerase used for?
Its use to convert glucose syrup into fructose syrup. Fructose is much sweeter so less is needed in foods the food is therefore are not so fattening. (But glucose and fructose have the same amount of calories).
59
What are carbohydrases used for?
Converting starch into sugar syrup for use in food
60
Advantages and disadvantages to using enzymes in industry:
Advantages:
In industry costs of equipment and energy can be reduced.
Enzymes in biological washing powder are very effective at removing stains such as blood, grass and gravy.
Some enzymes are used in medicine to diagnose, control or even cure diseases.
Biolgical washing powders can be used at lower temperatures - this saves energy and reduces costs.
Disadvantages:
Industrial enzymes can be costly to produce
Enzymes denature at high temperatures needed to kill pathogens in the washing.
Some fabrics, such as wool, will be digested by proteases
People may have allergic reactions on their skin.
Enzymes may enter waterways via the sewage system.
61
What does the net movement of particles in and out of cells depend on?
The concentration of the particles on either side of the cell membrane.
The larger the difference in concentration on either side, the faster the rate of diffusion.
The difference in concentration between the two areas is called the concentration gradient.
61
How do light and CO2 affect photosynthesis?
If the amount of CO2 or light is limited, they slow the rate of photosynthesis.
They're limiting factors.
They help increase the rate of photosynthesis until on of the other factors becomes limited.
62
Why do we need to digest food?
So that the food is changed from insoluble molecules into soluble molecules. Only then can the soluble molecules be absorbed into the blood.
63
What happens during photosynthesis?
Light energy is transferred into chemical energy.
Carbon dioxide is taken in by the leaves and water is taken by the roots.
The chlorophyll traps light energy needed for photosynthesis.
The energy is used to convert the CO2 and water into glucose - oxygen is a by-product.
Some of the glucose is converted into insoluble molecules for storage.
64
What's an enzyme?
A biological catalyst made up of proteins/chains of amino acids.
The active site of an enzyme is the area where the the substrate is held and broken down
65
What can enzymes do?
Build large molecules from smaller ones
Change one molecule onto another
Break down large molecules into smaller ones
66
Where are digestive enzymes made?
They're made by glands in the digestive system.
Digestive enzymes work outside the body cells in the cavity of the digestive system.
Specific enzymes digest each particular food type.
67
What are proteases used for?
Pre digesting proteins e.g. In some baby foods.
These enzymes which we can use are produced by microorganisms.
68
How does exercise effect the body?
Your muscles need more energy in order to contract therefore more glucose and oxygen is needed to be transported to the muscles.
To do this, there are changes in breathing and blood supply plus glycogen stored in the muscles is turned back into glucose for use during exercise.
This also means there's a greater need to remove more CO2.
By your breathing rate and depth of breathing increasing, a greater uptake of oxygen and release of CO2 at the lungs is allowed.
70
What's produced during anaerobic respiration?
It's inefficient since the breakdown of glucose is incomplete so, instead of CO2 and water, lactic acid is produced as a waste product.
Lactic acid causes muscle fatigue and when the exercise has finished, the lactic acid must be broken down.
A lot of oxygen is still needed to so this - the extra oxygen needed is known as oxygen debt.
Eventually the oxygen oxidises the lactic acid into CO2 and water.
71
Why is cell division necessary?
For growth of the organism or repair of the damaged tissues.
72
What is mitosis?
A form of asexual cell division where two identical cells are produced from the original cell.
The chromosomes contain the genes (alleles) which must be passed on to each new cell.
A copy of each chromosome is made before the cell divides and one of each chromosome goes to each new cell.
Two identical cells are formed by the simple division that takes place during mitosis. There are 23airs of chromosomes.
Making
Identical
Two
73
How does cell division in sexual reproduction work?
A two-stage process of cell division which reduces the chromosome number of the daughter cells. It is involved in making the gametes for sexual reproduction.
Cells in reproductive organs divide by meiosis to form sex cells (gametes).
Each gamete has only 1 set of chromosomes from each original pair (body cells have two sets). All cells are different from each other and the parent cells.
Sexual reproduction results in variation as the gametes from each parent fuse.
When gametes join at fertilisation, a single body cell wit new pairs of chromosomes is formed.
A new individual then develops by this cell repeatedly dividing by mitosis.
74
What's meiosis?
Before division, a copy of each chromosome is made.
The cell now divides twice to form four gametes (sex cells).
The chromosomes are separated using spindle fibres
Each gamete has a single set of chromosomes each with a different combination of genes.
```
(They then fuse with the opposite sex cell to form a full set of chromosomes)
Making Eggs (iosis)
```
75
Explain how four gametes are formed from one cell?
There are two sets of cell division.
| A body cell divides into two and each divides again.
76
What type of cells are produced by meiosis?
Sex cells - gametes
| Eggs and sperm
77
What are stem cells?
Undifferentiated cells with the potential to form a wide variety of different cell types.
They're unspecialised and are found in the human embryo and in adult bone marrow.
They can change into all the different types of body cell e.g. Nerve cells, muscle cells etc so we say the cells differentiate.
It's hoped that they can be used to treat/cure disorders such as paralysis e.g. By differentiating the cell into new nerve cells.
78
What are chromosomes?
Large molecules of DNA with a double helix structure.
79
What are genes?
Small sections of DNA.
Genes make up the chromosomes which control our characteristics.
Every individual, besides identical twins, base a unique DNA. People can be identified by their DNA fingerprint.
80
Who is Gregor Mendel?
A monk/scientist who worked out how characteristics were inherited.
He was the first person to suggest the idea of separately inherited 'factors'.
At first, people didn't accept his theory because scientists didn't know about chromosomes and genes until after he died.
81
What's a genetic code?
Each gene codes for a particular combination or order of amino acids which make a specific protein.
82
What chromosomes are found in humans?
```
Humans have 23 pairs if chromosomes.
Females have (XX) 2 X and makes have an x and y (XY).
```
83
What are alleles?
A version of a particular gene.
| Genes controlling the same characteristics.
84
What is the dominant?
The allele which 'masks' the effect of the other gene.
85
What is the recessive?
The allele where the effect is 'masked' by the other gene.
86
Hat are genetic terms and models?
Genetic diagrams are biological models which can be made to predict and explain the inheritance or particular characteristics.
Punnet squares are grids used to insert the alleles' symbols.
```
The correct terminology must be used:
Phenotype
Genotype
Homozygous
Heterozygous
```
87
What does phenotype mean?
Physical appearance of the characteristic e.g. Dimples or no dimples
88
What does genotype mean?
Genetic make up - which alleles does the individual inherit? DD, Dd or dd
89
What does homozygous mean?
Both alleles are the same - DD (homozygous dominant) or dd (homozygous recessive).
90
Hat does heterozygous mean?
The two alleles are different - Dd
91
What are genetic disorders and give examples:
Disorders caused by genes which can be inherited - caused by both dominant and recessive alleles.
If the allele is dominant, the person only has to inherit one dominant allele to have the disorder e.g. Polydactyly (born with extra toes or fingers).
If the allele is recessive, the person must inherit 2 recessive alleles to have the disorder e.g. Cystic fibrosis (affecting cell membranes and producing thick mucus). The allele must be inherited from both parents to develop cystic fibrosis.
By using diagrams, we can see how a disorder has been inherited and we can predict if offspring will inherit it.
(If a parent is heterozygous, for polydactyly, each child has a 50% chance of inheriting the disorder.
If both parents are heterozygous, for cystic fibrosis, each child has a 25% chance of inheriting the disorder.
The outcomes can be shown in a Punnet square.
92
What are embryonic stem cells used for?
They can be used in medical research and treatments.
Embryos can be screened for genetic disorders.
People are concerned because the research is experimental, the embryos have the potential to be babies and are destroyed, the embryo can't give permission and the research is expensive.
93
What's embryo screening?
Tests carried out in the embryo to diagnose possible disorders.
94
What are the beliefs in the origin of the earth?
It's believed that Earth is approx 4500 million years old and life began 3500 million years ago but scientists can't be exact since there's little repeatable or reproducible evidence.
Fossils are the remains of organisms from many years ago found in rocks - formed by preserved traces like footprints, hard parts like bone etc.
We can learn from fossils how different organisms changed as life developed. Many early life forms with soft bodies whoever left now traces behind (no fossils).
95
What is extinction and what causes it?
An entire species dying out
```
Caused by:
A new predator
Catastrophic events
Natural changes
New diseases
```
96
How does isolation effect the evolution of new species?
New species can arise from existing species is a group becomes isolated form the rest.
E.g. Graphical isolation may take place, separating an island from the mainland and isolation the organisms.
Those left on the island would be exposed to different conditions, food availability and predators.
Natural selection would take place in both areas however different characteristics would be necessary in the different groups. This results on two separate species.
In an isolated population, alleles are selected which would increase the chances of survival in the new location.
97
What's speciation?
The formation of new species.
These new species can occur following the separation of two populations e.g. Graphical isolation.
Each population has a wide range of alleles which control their characteristics, this is genetic variation.
These selected alleles help the organisms to survive and breed.
If the environment, competitors, food supply, predators etc are different, they will evolve differently.
Speciation occurs when two populations can no longer successfully interbreed.
98
What's meant by genetic variation?
The wide range of alleles which control the characteristics of a population.
99
What do DD, Dd and dd represent?
| Any letters
Alleles
100
What is anaerobic respiration?
The release of energy without the use of oxygen.
When muscles can't get enough oxygen for aerobic respiration, they respire anaerobically.
During anaerobic respiration, the glucose isn't completely broken down and lactic acid is produced - less energy is released from anaerobic respiration.
One cause of muscle fatigue is the build up of lactic acid.
Oxygen in the blood flowing through the muscles removes the lactic acid.
101
How can the distribution of organisms be measured?
Quantitative data to describe how physical factors might be affecting distribution e.g. by:
Random quantitative sampling using a quadrat (a square frame subdivided into a grid which can be used to count the number of a particular organism and estimate large scale)
Sampling along a transect (a line marked between two points where a quadrat is placed every so metres and organisms are counted) this is not random.
102
How is data made valid?
All possible variables are controlled
Results should be repeatable and reproducible
103
What is energy released by respiration used for?
Build larger molecules from smaller ones
Enable muscle contractions in animals
Maintain a constant body temperature
Build sugars, nitrates and other nutrients into amino acids then proteins in plants
104
What effect does exercise have on the body?
Muscles need more energy
The rate at which oxygen and glucose reaches the muscles and CO2 is removed increases
Heart rate increases and blood vessels supplying the muscles dilate to allow more oxygenated blood carrying glucose to reach the muscles
Breathing rate and depth increases allowing greater uptake of oxygen and release of CO2 at the lungs
Muscles store glucose as glycogen which can be converted back to glucose for respiration
105
What happens during exercise when the muscles become fatigued and stop contracting efficiently?
Muscles become tired and fatigued due to the lactic acid.
When muscles cannot get enough oxygen for respiration, they start to respire anaerobic ally.
The glucose is not completely broken down in anaerobic respiration and so lactic acid is produced.
Less energy is released from this type of respiration.
106
What reduces muscle fatigue?
Blood flowing through the muscles removes lactic acid.
When exercise is finished, this lactic acid must be broken down and a lot of oxygen is needed for this - this extra oxygen is known as oxygen debt which eventually oxidises the lactic acid into CO2 and water.
107
How is digestion sped up?
Protease enzymes in the stomach work best in acidic conditions.
Glands in the stomach wall produce HCl.
Amylase and lipase work in the small intestine, working best when conditions are slightly alkali
Bile produced by the liver is squirted into the small intestine and neutralises stomach acid.
108
What determines sex?
The X and Y chromosome
Men have an X and Y chromosome
Women have 2 X chromosomes.
109
What is Polydactyly?
An inherited condition caused by a DOMINANT allele where babies are born with extra fingers or toes.
Since the allele is dominant, the person only has to inherit one dominant allele to have the genetic disorder.
If A parent is heterozygous for polydactyly, a child has a 50% chance of inheriting the disorder (Ff, ff)
110
What is cystic fibrosis?
An inherited condition caused by a RECESSIVE allele where the allele affects cell membranes and causes the production of thick sticky mucus. The mucus can affect several organs including the lungs and pancreas.
The child must inherit a recessive allele from both parents to develop cystic fibrosis. The disorder can be passed on from two parents who don't have cystic fibrosis themselves.
The parents are described as carriers)
If both parents are heterozygous for cystic fibrosis each child has a 25% chance of inheriting the disorder (Ff, Ff)
111
How are scientists using stem cells and embryos for research?
Adult stem cells e.g. bone marrow cells are useful in treating some disorders such as leukaemia.
Use of embryonic stem cells has been investigated which have the potential to differentiate into a wide variety of cells.
The stem cells are taken from spare embryos from IVF, created from adult cells or taken from the umbilical cord of newborn babies
These could be used to grow new tissues and organs for transplant
Genetic tests, amniocentesis and embryo selection can be used to find the disease before the child is born (amniocentesis is a sample of the amniotic fluid / selection taking a selection from an embryo
112
What are the social economic and ethical reasons for and against embryo selection?
For:
- Healthy children require less medical intervention which costs the NHS less
- Society doesn't have to pay for treatment so money can be spent elsewhere
- It can stop potential suffering and limit parents' suffering
Against:
- The test is expensive
- It goes against certain religious beliefs
- Embryos which aren't selected are destroyed, killing life
113
How does a chromosome become to strands and explain why each chromosome must become two strands before the cell divides
Chromosomes become to strands because DNA copies itself.
Chromosomes must become two strands before the cell divides because you need one copy for each complete set of genetic material
114
What type of cell division produces gametes?
Meiosis
115
How can fossils be formed?
From the hard parts of animals that do not decay easily e.g. bones teeth
From parts of organisms that have not decayed because some of the conditions for decay were absent e.g. Fossils of animals preserved in ice
When parts of the organism or replaced by other material
As preserve the traces of organisms e.g. footprints
116
Many early lifeforms were soft bodied
| Explain why this makes it difficult for scientists to become certain about what early life forms were like
There soft bodies decomposed and decayed so that the skeletons couldn't be preserved in rock therefore there a lack of fossils
117
What may cause extinction?
A new disease
Changes in the environment of a geological time
New predator
A single catastrophe e.g. massive volcanic eruption
118
What is geographical isolation?
When two populations becomes physically isolated due to geographical features such as an island
119
How does geographical isolation cause speciation?
Geographical isolation could occur if an island separates from the mainland or if a new river separates two areas
The organisms left on the island may be exposed to different environmental conditions food or predators
Natural selection will occur in both areas for different characteristics will be beneficial in the two populations
Each population has a wide range of alleles that control their characteristics - this is genetic variation
Alleles that control the characteristics helping to survive a selected so the organisms with these alleles will survive and breed
If the populations are brought together and cannot interbreed we said that they belong to 2 separate species
120
When does speciation occurs?
Speciation, the forming of new species, occurs when the populations become so different that they cannot interbreed.
121
How do you answer adaption/speciation question?
1) Evolution takes place when there is natural variation within a population / ancestral populations are separated geographically and isolated
2) (some species may face different environments and conditions)
3) There is selection pressure and genetic variation. New alleles and mutations occur
4) Some individuals are now better adapted to the environment than others
5) They are more likely to survive breed and look after their offspring
6) These genes and alleles for the particular trait are passed on to their offspring
7) (Speciation) Eventually the two types can't interbreed
122
Why do plants need energy?
(to make) starch (for storage)
(to make) fat / oil (for storage)
(to make) amino acids / proteins / enzymes
(to make) cellulose / cell walls
123
Why are there gaps in fossil records?
* conditions not right for fossilisation
* geological activity has destroyed fossils / has destroyed evidence
* fossils not yet found
124
Person 1 was able to run much faster than Person 2.
Use information from Figure 7 and your own knowledge to explain why.
Person 1 sends more blood (to muscles / body / lungs)
(which) supplies (more) oxygen (and) supplies (more) glucose
(faster rate of) respiration or transfers (more) energy for use
removes (more) CO2 / lactic acid / heat
or less lactic acid made
or (more) muscle contraction / less muscle
125
What does lipase produce?
Fatty acids and glycerol
126
Name one organ where lipase is formed:
Pancreas
| Small intestine
127
Mendel thought that the production of a large number of offspring plants improved the investigation.
Explain why:
* fertilisation is random or ref. to chance combinations (of alleles / genes / chromosomes)
* more likely to get theoretical ratios or see (correct) pattern or get valid results if large number
* anomalies have limited effect / anomalies can be identified
