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AQA ADDITIONAL SCIENCE > BIOLOGY PART 1 and 2 > Flashcards

BIOLOGY PART 1 and 2 Flashcards

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Biology 101 flashcards
1
Q

Animal cells contain

A 
Nucleus 
Cell membrane 
Cytoplasm
Mitochondria
Ribosomes
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2
Q

Plant cells contain

A 
Nucleus 
Cell membrane 
Cytoplasm
Mitochondria 
Ribosomes
Cell wall
Chloroplasts 
Vacuole
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3
Q

Nucleus

A

Contains DNA and controls cell activity, and instructions for making new cells/organisms

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4
Q

Cell membrane

A

Controls what goes in and out of the cell

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5
Q

Cytoplasm

A

Liquid gel in which chemical reactions take place e.g. Respiration

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6
Q

Mitochondria

A

Structures in the cytoplasm where energy is produced during respiration

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7
Q

Ribosomes

A

Where protein synthesis takes place (making proteins from amino acids)

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8
Q

Cell wall

A

Made from cellulose to strengthen and supports the cell

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9
Q

Chloroplasts

A

Found in green parts of plants. Contains chlorophyll which absorbs light energy to make food by photosynthesis

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10
Q

Bacterial cells contain

A 
Cytoplasm
Cell membrane 
Cell wall
Loop of DNA
Capsule
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11
Q

Loop of DNA

A

Controls the cell, as bacterial cells do not have a nucleus

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12
Q

Capsule

A

Slimy capsule around outside of cell wall to protect it from antibiotics

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13
Q

Fungal cells are … than bacterial cells

A

Larger, and can be seen using a light microscope

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14
Q

A fungal cell wall is made of

A

Chitin

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15
Q

Why were bacterial cells discovered later?

A

Not enough advanced technology

Bacterial cells are much smaller

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16
Q

Yeast cells are a

A

Single celled organism

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17
Q

Yeast cells contain

A 
Nucleus
Cytoplasm 
Cell membrane 
Ribosomes 
Mitochondria
Cell wall
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18
Q

Palisade cell (from a leaf)

A

Absorbs light for photosynthesis

Contains chloroplasts which contain the pigment chlorophyll

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19
Q

Muscle cell

A

Contracts to provide movement

Contains mitochondria which provides the energy for contraction

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20
Q

Root hair cell

A

Absorbs water and mineral salts from soil

Hair like structure to increase surface area to absorb more water/minerals

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21
Q

Sperm cell

A

Fertilises female gamete
Tail to swim
Mid section is full of mitochondria for energy to swim

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22
Q

Red blood cell

A

Absorbs oxygen and transports it around the body
No nucleus - more haemoglobin can be packed in, more space to carry oxygen
Biconave shape so it’s flexible and fits through small capillaries

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23
Q

Ciliated cell (in oviduct)

A

Moves egg near uterus
Cilia on surface - beats regularly so egg moves down oviduct
Contains mitochondria for energy so cilia can move

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24
Q

Nerve cell (motor neurone)

A

Transmits nerve impulses
Contains fibres (dendrites) that connect to other neurones
Axon surrounded by myelin sheath to insulate and speed up transmission of nerve impulse

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25
Q

Diffusion

A

Movement of particles from a high area of concentration to a low area of concentration. No energy required

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26
Q

The greater the difference in concentration, the … the rate of diffusion

A

Faster

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27
Q

Diffusion occurs in

A

Gases and liquids

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28
Q

Why can diffusion not occur in solids?

A

Particles are not free to move

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29
Q

Large surface area … the rate of diffusion

A

Increases, more area is exposed so more diffusion can take place

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30
Q

Higher temperature … the rate of diffusion

A

Increases, the hotter it is the more kinetic energy for diffusion

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31
Q

The stomach is an organ that contains

A

Muscular tissue
Glandular tissue
Epithelial tissue

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32
Q

Muscular tissue

A

Contracts for movement

Churn up contents

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33
Q

Glandular tissue

A 
Produces hormones and enzymes
Produce digestive juices 
Layer of cells
Make chemicals e.g. Acid
Lines inside of organs
Creates thick mucus to coat cells
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34
Q

Epithelial tissue

A 
Cover outside and inside of stomach
Arranged evenly 
Smooth allowing organs to easily move 
Layers of cells 
Protective coat around the organ
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35
Q

Tissues

A

Groups of similar cells that work to carry out a particular function

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36
Q

Organs

A

Groups of different tissues that work to perform a certain function

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37
Q

Organ systems

A

Group of organs working together to perform a function, organ systems form organisms

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38
Q

Digestive system - Salivary glands

A

Produces the enzyme amylase in saliva

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39
Q

Digestive system - Liver

A

Bile is produced

  • neutralises stomach acid
  • emulsified fats
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40
Q

Digestive system - Gall bladder

A

Where bile is stored before released into small intestine

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41
Q

Digestive system - Large intestine

A

Where excess water is absorbed from undigested foods, producing faeces

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42
Q

Digestive system - Small intestine

A

Where digested foods are absorbed and move into the blood

Produces amylase, lipase and protease to complete digestion

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43
Q

Digestive system - Rectum

A

Where faeces are stored, before leaving through the anus

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44
Q

Digestive system - Pancreas

A

Produces protease, amylase and lipase and releases them into the small intestine

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45
Q

Digestive system - Stomach

A 
Pummels food with its muscular wall
Produces protease, amylase and lipase
Produces hydrochloric acid 
- to kill bacteria
- give correct pH for protease enzymes to work (pH2 - acidic)
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46
Q

How are cone cells in the eye adapted to carry out its function?

A
  • Outer segment of cell has a chemical called visual pigment - chemically changes in colour to allow you to see in colour
  • The centre has lots of mitochondria, releases energy allowing visual pigment to reform
  • Specialised nerve cell that transmits signals to brain so colour is continuously seen
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47
Q

How are fat cells adapted?

A
  • small cytoplasm to allow space for fat to be stored
  • few mitochondria as they do not use much energy
  • can grow to 1000 times its original size
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48
Q

Tissues - examples?

A

Epithelial
Muscle
Blood
Bone

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49
Q

Organs - examples?

A 
Stomach
Heart
Kidney
Lung
Skin
Small intestine
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50
Q

Organ systems - examples?

A 
Brain
Circulatory 
Digestive
Glandular
Nervous
Skeletal
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51
Q

Pancreas and salivary glands make digestive juices that

A

Lubricate food

Carry enzymes to aid digestion

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52
Q

Digestion

A

Breakdown of large food molecules into smaller particles that can pass through the gut wall and be absorbed into the blood

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53
Q

Absorption

A

Process by which smaller food particles are taken into the blood. They pass through the gut-wall into the blood from the gut environment

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54
Q

Plant organs contain

A

Stem
Roots
Leaves

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55
Q

Organ: stem

A

Supports the plant

Transports substances through the plant

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56
Q

Organ: leaf

A

Produces food by photosynthesis

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57
Q

Organ: roots

A

Anchors the plant

Takes in water/minerals from the soil

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58
Q

Leaf - upper epidermal tissue

A

Thin and transparent
Waxy cuticle
Allows light to pass to the mesophyll to protect the leaf and stop water loss

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59
Q

Leaf - palisade mesophyll

A

Regular shaped cells
Near upper surface
(Where most chloroplasts are found)
Absorbs the maximum amount of sunlight

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60
Q

Leaf - spongy mesophyll

A

Irregular shaped cells
Air spaces
Increases surface area for CO2 absorption to maximise
Allows gases to diffuse

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61
Q

Leaf - lower epidermal tissue

A

Surrounded by guard cells
Allows gases to diffuse
Guard cells open/close stomata

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62
Q

Leaf: vascular bundles

A

Contains xylem and phloem tubes

Transport substances from roots to the shoots and leaves

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63
Q

Leaf - guard cells

A

Opens and closes stoma to allow gas exchange

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64
Q

Why do plants need glucose?

A
  • used in respiration to release energy
  • joined together to make starch for storage
  • combined with nutrients to make proteins for growth
  • joined to make cellulose for cell walls
  • converted to fats and oils for the seeds
  • converted to fructose for the fruit
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65
Q

Photosynthesis equation

A

Carbon dioxide + water -> (light energy) -> oxygen + glucose

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66
Q

Limiting factors - photosynthesis

A

Light intensity
CO2
Temperature

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67
Q

What happens during photosynthesis?

A

Light energy is absorbed by chlorophyll (in chloroplasts)
The energy is used during by converting CO2 from the air and water from the soil into sugar (glucose)
Oxygen is a by product

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68
Q

Photosynthesis - light intensity

A

A shortage of light means less energy to power the reaction

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69
Q

Photosynthesis - temperature

A

A low temperature limits the rate of photosynthesis as molecules move slower so there are less reactions, however too high will cause enzymes to be denatured (40 degrees roughly)

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70
Q

Photosynthesis - CO2 concentration

A

This will limit the rate as there are less molecules in the reaction. A levelled off line on the graph shows it has reached its optimum point.

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71
Q

How can you grow plants in the ideal environment?

A

Grow then in a greenhouse as limiting factors can be controlled

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72
Q

Uses of glucose (from photosynthesis) in plants and algae

A

Converted into insoluble starch for storage

Used in respiration

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73
Q

Physical factors affecting organisms

A 
Temperature
Availability of nutrients 
Availability of light 
Availability of water
Availability of oxygen 
Availability of CO2
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74
Q

How temperature affects organisms

A

Affects the rate of an organisms metabolism
Some cannot tolerate extreme temperatures
Organisms with a high temperature may also struggle to tolerate extreme conditions

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75
Q

How availability of nutrients affects organisms

A

Nutrients e.g. Nitrate are essential for growth of plants/microorganisms
A low concentration would cause organisms to struggle to grow and survive

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76
Q

How availability of light affects an organism

A

Required as an energy source for photosynthesis

In low light intensities, plants grow very slowly

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77
Q

How availability of water affects organisms

A

All organisms require water
Chemical reactions take place in water solutions
An absence of water causes cells and in turn, organisms to die

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78
Q

How availability of oxygen affects organisms

A

Essential for aerobic respiration
May become limited in soil - so roots cannot grow and absorb the minerals/water
May become limited in water, so aquatic organisms struggle to respire

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79
Q

How availability of CO2 affects organisms

A

Essential for photosynthesis

Limited where there are many plants - reducing rate of growth

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80
Q

Water and CO2 are used to … food during respiration

A

Synthesise

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81
Q

Phosphate - plants

A

For growth and respiration
Component of DNA
Deficiency symptom - discoloured leaf and poor growth

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82
Q

Magnesium - plants

A

Makes chlorophyll green

Deficiency symptom - chlorophyll goes yellow

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83
Q

Nitrate - plants

A

Found in water, creates amino acids which create proteins

Lack of nitrate - stunted growth

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84
Q

Potassium - plants

A

For photosynthesis and respiration
Must be present for respiration enzymes to work
Deficiency symptom - discoloured leaves and poor growth

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85
Q

Transect

A

A line across a habitat/ part of a habitat

The number of organisms of each species can be observed and recorded at regular intervals along the transect

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86
Q

Quadrat

A

Organisms underneath, usually plants, can be identified and counted

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87
Q

Why should quadrats be randomly placed?

A

So a representative sample is taken

The validity and reproducibility of the results increases as the results from more quadrats are analysed

88
Q

Proteins

A

Made up of long chains of amino acids

Fold into a specific shape which dictates its function, another molecule will then fit into it

89
Q

Uses of proteins in the body

A 
Keratin in the hair/skin
Channels in cell membrane
Hormones
Haemogoblin in red blood cells 
Antibodies
Collagen in blood vessel walls, skin, tendon and bones
Fibrin in blood clots (scabs)
Elastin in lungs/blood vessel walls
90
Q

Catalysts

A

Substances that speed up reactions without being changed or used up

91
Q

Biological catalysts

A 
Enzymes, enzymes are proteins
Found in long chains 
Speed up reactions 
Specific (only catalyse a particular reaction)
Re-used
92
Q

All proteins contain the elements

A 
Carbon
Oxygen
Nitrogen
Hydrogen
Some sulphur
93
Q

Reactions sped up by catalysts

A

Proteins
Respiration
Proteinsynthesis

94
Q

You can change the shape of a protein by

A

Heating it
Changing its pH
Reacting it with chemicals e.g ethanol

95
Q

What happens if a proteins shape changes?

A

It will not be able to carry out its function

It will be denatured

96
Q

How does pH affect the active sight?

A

It effects the forces that hold the enzyme molecule together

97
Q

What factors affect enzymes

A

pH

Temperature

98
Q

Active sight

A

A specific shape that only a certain type of reactant (substrate) will fit into

99
Q

How do enzymes affect activation energy?

A

It lowers the activation energy, so reactions occur at a greater rate
Particles do not need to collide with as much energy

100
Q

How does temperate affect the rate of reaction with enzymes?

A

If it is too low, the rate of reaction falls as there is less kinetic energy
If it is higher, particles collide with more energy so the rate of reaction increases
If it is too high, the enzyme denatures and the active sight shape changes so the substrate can no longer bond. The rate of reaction falls

101
Q

Digestive enzymes

A

Break down big molecules into smaller ones

102
Q

Big molecules (digestion - examples)

A

Starch
Proteins
Fats

103
Q

Small molecules (digestion - examples)

A

Sugars
Amino acids
Glycerol
Fatty acids

104
Q

3 enzymes - digestive system

A

Amylase
Protease
Lipase

105
Q

Amylase

A

Concerts starch into maltose and other sugars

106
Q

Protease

A

Converts protein into amino acids

107
Q

Lipase

A

Converts lipids into glycerol and fatty acids

108
Q

Where is amylase made?

A

Salivary glands
Pancreas
Small intestine

109
Q

Where is protease made?

A

Stomach (pepsin)
Pancreas
Small intestine

110
Q

Where is lipase made in?

A

Pancreas

Small intestine

111
Q

How does bile emulsify fats?

A

Breaks fats into tiny droplets

There is then a larger surface area of fat for lipase to work with so digestion is quicker

112
Q

How does bile neutralise acid in the stomach?

A

The hydrochloric acid in the stomach makes the pH too acidic for enzymes to work
Bile is alkaline so it neutralises the acid

113
Q

Where is bile stored and released into?

A

Stored in the call bladder

Released into small intestine

114
Q

Biological washing powders

A

Contain enzymes (protease/lipase) to break down fats and proteins in stains

115
Q

Enzymes must work well in solutions with a high pH because washing powders are

A

Highly alkaline

116
Q

What is the range of temperatures enzymes must work at

A

10-90 degrees

117
Q

When can enzymes be used in home and industry?

A

If microorganisms produce enzymes that pass out of the cells

118
Q

Biological detergents are more effective at … temperatures

A

Lower

119
Q

Advantages of biological washing powders

A

Enzymes work at low temperature saving energy
More efficient at removing stains
Help delicate fabrics get cleaned without damaging then by a hot wash

120
Q

Disadvantages of biological detergents

A

May lead to allergies and irritation

If clothes are not rinsed, the enzymes may remain in the clothing which would digest protein in the skin

121
Q

Enzymes used in industry

A

Biological washing powders
‘Pre-digested’ baby foods
Diet foods/slimming products
Fruit juice

122
Q

How does the function of enzymes affect confectionary/slimming products?

A

Breaks cheap starch into glucose

This changes to fructose syrup (by isomerase) so less of it if needs to get a sweeter taste

123
Q

How does the function of enzymes affect baby food?

A

Protease ‘pre-digests’ the proteins so it is easier for the babies to eat and absorb into their blood

124
Q

How does the function of enzymes affect fruit juice?

A

It makes it sweeter

125
Q

How does the function of enzymes affect meat?

A

It tenderises and makes it softer

126
Q

Properties of industrial enzymes

A

Long shelf life
Withstand high temperatures
Can work in the presence if chemicals that would otherwise stop enzymes working

127
Q

Enzymes in the home

A

Used to break down food stains as biological detergents

128
Q

Advantage of enzymes

A

Enzymes lower the temperatures and pressures often needed for chemical reactions
They are specific
Biodegradable

129
Q

Disadvantages of enzymes

A

Sensitive to surroundings (changing pH or temperature may stop them working)
Expensive to control the conditions

130
Q

Respiration

A

The process of releasing energy from glucose, which goes on in every cell

131
Q

Aerobic respiration

A

glucose + oxygen -> carbon dioxide + water + energy

132
Q

Aerobic respiration is respiration using…

A

Oxygen

133
Q

Aerobic respiration occurs inside…

A

Mitochondria

134
Q

The energy respiration releases is used to…

A
  • Build larger molecules from smaller ones (proteins from amino acids)
  • Allow muscles to contact in animals
  • Allow birds/mammals to maintain a constant body temperature
  • In plants to build up sugars, nitrates and nutrients into amino acids which are built into proteins
135
Q

Cyanide

A

A toxin that stops respiration by stopping enzymes involved in the process from working

136
Q

How can exercise affect us?

A

The depth and rate of breathing increases
Heart rate increases
Increases supply of blood flow to muscles of sugar/oxygen
Removal of CO2 increases

137
Q

How is glycogen used during exercise?

A

Glucose from food can be stored as glycogen
Mainly stored in the liver but each muscle has its own store
During vigorous exercise, glucose can be converted back to glucose to provide further energy

138
Q

Anaerobic respiration

A

Glucose -> lactic acid + (some) energy

139
Q

Anaerobic respiration is respiration without

A

Oxygen

140
Q

What is anaerobic respiration?

A

The incomplete breakdown of glucose into lactic acid. It does not release as much energy as aerobic respiration but is useful in emergencies

141
Q

Lactic acid - anaerobic respiration

A

Lactic acids builds up in muscles, which is painful.

It tires out muscles- they stop contacting efficiently

142
Q

What is oxidation?

A

Blood flows through the muscles to removed the lactic acid by oxidising it to CO2 and water

143
Q

Every cell contains … pairs of chromosomes

A

23

144
Q

What is a gene?

A

A section of DNA

145
Q

What is a chromosome?

A

Made up of DNA

146
Q

What is a diploid number?

A

A full set (23 pairs of chromosomes)

147
Q

Sex cells only have … single chromosomes

A

23

148
Q

What is mitosis?

A

Mitosis is when a cell reproduces itself by splitting to form two identical offspring

149
Q

Mitosis makes new cells for…

A

Growth
Repair damaged tissue
Replace worn out tissue

150
Q

DNA fingerprinting is used for…

A

Forensic science

Paternity testing

151
Q

What do genes do?

A

They code for a specific protein

They tell cells the order for the amino acids

152
Q

What is the exception to everyone having unique DNA?

A

Identical twins

Clones

153
Q

Before cells divide in mitosis, what must happen?

A

The DNA must make a copy of itself

154
Q

How does DNA make a copy of itself?

A

DNA is double stranded
The molecule unzips
This exposes DNA based
These bases then join to spare, complimentary bases
The bases then match to create an exact copy

155
Q

Which DNA bases join together?

A

A - T
T - A
C - G
G - C

156
Q

Mitosis is … reproduction

A

Asexual, so there is no variation

157
Q

How does the cell create an exact copy of itself in mitosis?

A

DNA replicates
The two duplicated chromosomes like up in the centre of the cell
Spindle fibres form
Each chromosome splits into two identical copies
Each copy moves to opposite ends of the cell
A membrane forms around each set
This becomes the nuclei
The cytoplasm then divides leaving two new cells that are identical

158
Q

Meiosis

A

Produces cells which have half the number of chromosomes (gametes)

159
Q

Where does meiosis occur and what does it result in?

A

It happens in sex organs and results in variation

160
Q

Before meiosis occurs what should happen?

A

Before the cell divides, it duplicates its DNA

161
Q

How does a cell create gametes through meiosis?

A

In the first division, chromosome pairs line up in the centre
The pair gets pulled into two separate cells as they are attracted to opposite poles (each cell has one copy of each chromosome)
In the second division, they line up again in the centre and split
You are left with four gametes each with a single set of chromosomes

162
Q

Why does meiosis occur?

A

For sexual reproduction

163
Q

What happens to gametes during fertilisation?

A

A single body cell with new pairs of chromosomes are formed

This cell then divides repeatedly by mitosis to develop into a new individual

164
Q

What are stem cells?

A

Embryonic stem cells can turn into any type of cell

165
Q

Where can stem cells be found?

A

Adult bone marrow

Human embryos

166
Q

What is differentiation?

A

The process by which a cell changes to become specialised for its job

167
Q

Are stem cells undifferentiated?

A

Yes

168
Q

How can stem cells be used?

A

Nerve cells- helping those paralysed by spinal cord injuries
Beating heart muscle cells- those with heart disease
Insulin producing cells- those with diabetes

169
Q

Arguments for stem cells

A
  • those who are alive are more important than an embryo
  • unwanted embryos from fertility clinics could be used instead
  • medicine uses them to cure disease
  • could replace faulty cells
170
Q

Arguments against stem cells

A
  • each embryo is a potential human life

- scientists should find other ways to obtain stem cells rather than using them from embryos

171
Q

In asexual reproduction, the offspring contain the … alleles as the parent

A

Same (they are genetically identical)

172
Q

Why does variation occur in sexual reproduction?

A

When the gametes fuse, one of each pair comes from the parents

173
Q

What determine the sex of the offspring?

A

One of the 23 pairs of chromosomes is different, and carries the gene that determines sex

174
Q

Which chromosomes determine male characteristics?

A

All men have an X and a Y chromosome

The Y chromosomes causes the male characteristics

175
Q

What chromosome determines the female characteristics?

A

All women have to X chromosomes

The combination of XX is what allows female characteristics to develop

176
Q

What is an allele?

A

An allele is a version of a gene

E.g. The gene could be Hh and the alleles would be H and h

177
Q

What is a dominant allele?

A

It controls the development of a characteristic when it is present in only one of the chromosomes

178
Q

What is a recessive allele?

A

It controls the development of characteristics only if the dominant allele is not present

179
Q

What is a genotype?

A

What alleles you have

180
Q

What is a phenotype?

A

The characteristic displayed by the genotype

181
Q

What is a heterozygous?

A

2 different alleles

182
Q

What is a homozygous?

A

2 of the same alleles

183
Q

Who worked out the main principles of inheritance?

A

Gregor Mendel

184
Q

What 3 conclusions did Mendel reach?

A
  • Characteristics in plants are determined by “hereditary units”
  • Hereditary units are passed on from both parents (one unit from each parent)
  • Hereditary units can be dominant or recessive - if an individual has both, the dominant characteristic will he expressed
185
Q

What are hereditary units?

A

Genes

186
Q

Why were Mendel’s discoveries not recognised until after his death?

A

He published his work in an obscure journal
DNA, chromosomes and genes were not discovered yet
People couldn’t accept the link between plants and animals
He was a monk, so wasn’t as respected

187
Q

What does DNA stand for?

A

Deoxyribose Nucleic Acid

188
Q

How do genes control characteristics?

A

DNA forms a helix that protects it
Phosphate backbone
Bases

189
Q

Why do the bases match together?

A

The shape of the molecule allows them to fit together

190
Q

Chromosomes have … folded DNA

A

Tightly

191
Q

What are the four bases called?

A

Cytosine & Guanine

Adenine & Thymine

192
Q

What is a triplet code?

A

Three bases joined with the opposite base

193
Q

One triplet code creates an…

A

Amino acid

194
Q

A chain of amino acids make a…

A

Protein

195
Q

What forms the bond between bases?

A

A hydrogen bond

196
Q

What is cystic fibrosis?

A

Genetic disorder of cell membranes

Body produces sticky mucus in air passages/ pancreas

197
Q

Cystic fibrosis - explain the alleles

A

The allele that causes the disease is recessive ‘f’
People with only one ‘f’ will not have the disorder (carriers)
To get the disorder, both parents must be carriers or sufferers
E.g. 1 in 4 chance if parents are both carriers
Only a sufferer if you have two ‘f’ alleles

198
Q

What is Polydactyly?

A

Genetic disorder where baby’s are born with extra fingers/toes
Not life threatening, little side effects

199
Q

Polydactyly - explain the alleles?

A

Caused by the dominant allele ‘D’
Can be inherited if one parent carries the defective allele
The parent with that allele will also suffer as the allele is dominant
E.g. 50% chance of child having disorder if one parents has the ‘D’ allele

200
Q

What is embryo screening?

A

The screening of embryos to search if their alleles may cause a genetic disease m

201
Q

Arguments for embryo screening

A

Stops people suffering
There are laws to stop it going too far
During IVF most embryos are destroyed anyways, this just allows the selected one to be healthy
Treating disorders is expensive

202
Q

Arguments against embryo screening

A

People may use screening to pick their most desirable baby
Rejected embryos were potential human life
Screening is expensive
Implies those with disorders are ‘undesirable’ which increases prejudice

203
Q

What is speciation?

A

The development of a new species

204
Q

What 2 things lead to speciation?

A

Isolation

Natural selection

205
Q

What is a species?

A

A group of similar organisms that reproduce to give birth the fertile offspring

206
Q

Why does speciation occur?

A

When populations of the same species become so different they can no longer breed to produce fertile offspring

207
Q

What is isolation?

A

When a population is levies is separated

208
Q

What are the 4 stages of speciation?

A

Isolation - 2 species become separated
Genetic variation - they show variation because of the range of alleles
Natural selection - pass on characteristics to next generations
Speciation - populations become so different that interbreeding is no longer successful

209
Q

Extinction happens if you can’t … quickly enough

A

Evolve

210
Q

Reasons species become extinct

A
  • new predators
  • more competition
  • catastrophic event e.g volcano
  • diseases
  • new species develops (speciation)
  • change in environment
211
Q

What are fossils?

A

The remains of plants and animals

212
Q

3 ways fossils form in rock

A
  • Gradual replacement by minerals (most common)
  • Casts and impressions
  • Preservation in places where no decay occurs
213
Q

How does gradual replacement by minerals cause fossils to form?

A

Thing like bones do not decay easily
They get replaced by minerals as they decay and form a rock like substance shaped like the original bone/shells/teeth etc.
The surrounding sediment turns to rock but the fossil stays distinct in the rock

214
Q

How do casts and impressions lead to fossils?

A

Fossils can form if the organism is buried in a soft material like clay
The clay hardens and the organism decays leaving a cast
E.g a plants roots can be preserved as casts
Things like footprints leave impressions in soft materials

215
Q

How does preservation lead to fossils forming?

A

-In tar pits/ amber (clear yellow stone made from fossilised resin) there’s no oxygen or moisture
Therefore decay microbes cannot survive
-In glaciers it’s too cold for decay microbes to work
-Peat bogs are too acidic for decay microbes

216
Q

Why can we not be sure on how life began?

A

Lack of valid and reliable evidence
This is because it’s believed early organisms were soft bodied and decayed completely
Therefore the fossil record is incomplete
Geological activity may have destroyed fossils e.g tectonic plates moving

AQA ADDITIONAL SCIENCE (3 decks)

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