Life On Earth Flashcards
1
Q
What is biodiversity?
A
Total variety of all living things on Earth.
2
Q
What is a habitat?
A
The place where a organism lives.
3
Q
What is a population?
A
All the members of one species living in a habitat.
4
Q
What is a community?
A
All the different organisms living in a habitat.
5
Q
What is an ecosystem?
A
All the living organisms in a habitat + the non-living components with which they interact.
6
Q
What is a producer?
A
Green plant that makes its own food by photosynthesis.
7
Q
What is a consumer?
A
Organism that eats a producer / another consumer for energy.
8
Q
What is a herbivore?
A
Organism that eats only plant material.
9
Q
What is a carnivore?
A
Organism who only eats animal material.
10
Q
What is a niche?
A
The role an organism plays within a community.
11
Q
What is an omnivore?
A
Organism that eats both plant and animal material.
12
Q
What is a predator?
A
Organism that hunts other animals for its food.
13
Q
What is a prey?
A
Organisms hunted by a predator.
14
Q
What is a species?
A
A group of organisms that can interbreed to produce fertile offspring.
15
Q
What is a food chain?
A
A diagram which shows how energy is passed on from one organism to another in an ecosystem, when they are eaten.
16
Q
What does a food chain always start with?
A
Producer
17
Q
What do the arrows in a food chain represent?
A
Direction of energy flow
18
Q
Organise these organisms into a food chain: lion, grass, zebra.
A
grass → zebra → lion.
19
Q
What are the three ways that energy is lost from a food chain?
A
Heat, movement, undigested material.
20
Q
Refer to this food chain:
zoo plankton → animal plankton → clownfish → shark.
What will happen to the number of clownfish and zooplankton if the shark becomes vegetarian?
A
Clownfish: Increase because they are not being eaten by sharks anymore.
Zooplankton: decrease because they are eaten by sharks.
21
Q
What is a pyramid of numbers?
A
Diagram that represents the number of organisms at each stage.
22
Q
What is a pyramid of energy?
A
Represents the energy available at each stage of a food chain. As energy is lost at each stage, it is always a pyramid shape.
23
Q
When will competition between organisms occur?
A
When they require the same resources but they are in short supply.
24
Q
What might animals compete for?
A
Food, water, shelter, mates
25
What might plants compete for?
Light, water, soil nutrients, root space.
26
What are the two types of competition?
Intraspecific and interspecific
27
Give an example of intraspecific competition?
**Polar bears fighting** for one prey animal.
28
Give an example of Interspecific competition.
Rabbits and cats fighting for shelter.
29
What type of competition is more intense?
**Intraspecific**, because it is **for all resources required**.
30
What are the two types of factors that affect biodiversity?
Abiotic, biotic
31
What are abiotic factors?
**Non-living** factors
32
What are biotic factors?
Factors **directly related to living organisms**.
33
Describe how soil pH can be measured
Insert the **probe** of a **pH meter** into the soil and take a reading
34
What are examples of biotic factors?
Predation, competition, food availability, disease, grazing
35
Describe how light intensity can be measured
Direct the **solar panel** of a **light meter** towards the **light source** being measured and take a reading
36
What are examples of abiotic factors?
Temperature, pH, moisture, light intensity.
37
Describe how temperature can be measured
Insert a **thermometer** into the **soil** and take a reading
38
How can predation affect biodiversity?
**Affects the numbers of population** of **prey** and **predators**. The two will have a **delicate balance**.
39
Describe how the moisture level can be measured
Insert the **probe** of a **moisture meter** into the **soil** and take a reading
40
How can disease affect biodiversity?
Could **remove whole species** from food webs.
41
What are quadrats?
Quadrats **mark off an exact area** of ground so that the **organisms** in that area **can be identified** and **counted**.
42
What sources of error occur when measuring soil pH and how can they be minimised?
- Reading may be **contaminated** from a **previous measurement**
- **Wipe the probe clean** between **each use**
43
What sources of error occur when measuring light intensity and how can they be minimised?
- Sensor could be **blocked**
- Stand to the **side** of the meter when taking a reading
44
What are some sources of error regarding quadrats and how can you minimise them?
**Sources of error**:
- Non-random sampling
- Sample size too small
**How to minimise**:
- Throw quadrat at random
- Throw many quadrats
45
What are transects?
A **line across a habitat** or part of it. It can be a **string or a rope** placed **on the ground**. The number of organisms can be observed and recorded along the transect.
46
What sources of error occur when measuring soil moisture and how can they be minimised?
- Reading may be **contaminated** from a previous measurement
- Wipe the probe **clean and dry** between each use
47
What sources of error occur when measuring temperature and how can they be minimised?
- Reading may be **inaccurate**
- Leave it for some time to **adjust** before taking a reading
- Or you insert the probe to the **same depth** each time
48
What is the word equation for photosynthesis?
carbon dioxide + water (light energy + chlorophyll) → oxygen + glucose
49
Where does photosynthesis take place?
Chloroplasts
50
What is chlorophyll?
A **chemical** found **in the chloroplasts** of plant cells.
51
What method can be used to represent the population of organisms in an ecosystem?
A **sample**
52
What is the function of chlorophyll?
To **absorb light energy** and **convert it to chemical energy in ATP**.
53
What are the two stages of photosynthesis?
Light reactions and carbon fixation
54
What would you use to sample small, invertebrate animals?
**Pitfall traps**
55
What happens in the light reactions stage?
The **light energy absorbed by chlorophyll** is converted into **chemical energy**. Some of this energy used to **split water** into hydrogen and oxygen. Some of the chemical energy is used to make **ATP from ADP + Pi**. The **oxygen** is a **by product** which is **released from the leaf by diffusion**. The **hydrogen is carried forward** to carbon fixation.
56
What is carbon fixation controlled by?
Enzymes.
57
Give some sources of error of pitfall traps, its problems associated with them and how to fix them.
- Trap **not level with soil surface**, organisms don’t fall in**, make sure trap is **level** with soil so insects fall in
- Too many **fall into the trap** because it was left for **too long**, organisms **eat** each other, don’t leave trap for **too long**
- Trap **not camouflaged**, **predation** occurs, **camouflage** the trap
- No **drainage holes**, trap **floods** and **organisms lost**, make drainage holes **small enough** but not too big so organisms don’t **fall out**
58
What happens in carbon fixation?
The **ATP and hydrogen produced** during the light reactions **are used**. The **energy from ATP allows hydrogen to join with** the gas **carbon dioxide** to **form sugar**.
59
What are the 3 limiting factors of photosynthesis
- **Light intensity**
- **Temperature**
- **Carbon dioxide** concentration
60
The sugar produced contains chemical energy. What is the sugar used for?
**Respiration**, **converted to starch** for storage, **converted to cellulose** to build up the cell wall.
61
Why is temperature a limiting factor?
Because photosynthesis is an **enzyme-controlled reaction**
62
How can you measure the rate of photosynthesis?
Measure the number of **oxygen bubbles** per minute
63
How can you determine limiting factors on a graph?
- When the line is **diagonal**, then the limiting factor is the one on the **x-axis**.
- When the line is **horizontal**, then the limiting factor one that’s **not the one being measured**.
64
What are some farming techniques that have been used to increase food production?
Fertilisers and pesticides.
65
How do plants obtain nitrogen?
In the form of **nitrates** which are **dissolved in soil water** and **absorbed by roots**
66
What are nitrates used to produce?
**Amino acids**, which are synthesised into **proteins**.
67
What is biological control?
Biological control involves using animals that are **natural predators** to keep numbers of **pests** down
68
Where is biological control useful?
In areas where pests have been introduced to a **habitat** where there are **no natural predators**
69
What are genetically modified crops?
This involves taking a useful **gene** from **one organism** and inserting it into **another**.
70
What is the benefit of using genetically modified crops?
GM crops can **metabolise nitrogen** more effectively, reducing the **need** for **fertilisers** and **increasing yields**
71
What is an indicator species?
Species whose **presence/absence** can show the **conditions** of an environment
72
What is a mutation?
A mutation is a **random change** to **genetic material**. Mutations are **spontaneous** and the only source of **new alleles**
73
What are types of mutations?
- Neutral
- Advantageous
- Disadvantageous
74
Describe how an algal bloom forms and its effects.
**Fertilisers** that are sprayed onto crops can **leach into freshwater**, adding **unwanted nitrates**.
Fertiliser greatly **increases growth of algae**, causing **algal bloom** after which, the **algae die**.
Algal blooms **reduce light levels**, meaning that **plants can’t photosynthesise and die**.
**Dead plants and dead algae** become **food for bacteria** which greatly **increase** in number.
Bacteria use **large quantities of oxygen**, so there is **less oxygen** for **other organisms** in freshwater, causing them to **die**.
75
What are pesticides used for?
**Killing** a range of **pests** that **reduce crop yield**.
76
What is an unintended effect of pesticides?
Pesticides **aren’t biodegradable** so they have to be **broken down by the organism** that ingests them.
The **toxicity levels** of this **increase** as you **go up the food chain** because **organisms become larger** and **eat more** from the level below.
77
What is bioaccumulation?
The **build up of toxic substances in living organisms**.
78
What do new alleles produced by mutation allow plants and animals to do?
Adapt to **changing environmental conditions**
79
What is an adaptation?
An **inherited characteristic** that makes an organism well suited to be able to **survive** its environment
80
What is natural selection?
A process where organisms are **better adapted** to their environment **survive and reproduce**, passing on their **favourable alleles**.
Those organisms less well-adapted **die** before they reproduce
81
How does natural selection occur?
When there are selection pressures such as:
- **Temperature**: some might be better adapted to **colder** temperatures
- **Predators**: some organisms might be better adapted to **camouflage** and avoid predators
82
Describe the process of natural selection.
**Species produce more offspring** than the **environment can sustain**.
**Variation** then exists **between members of a species**.
The **best adapted survive**
**Those who survive reproduce** passing on their **favourable alleles** that **give a selective advantage**
This happens **over many generations** and these **alleles increase in frequency** within the population.
83
Define speciation.
The **evolution of new species** from **a pre existing one**.
84
Under what condition will speciation occur?
When **sub-populations become isolated from each other** and so **can’t interbreed**.
85
What are some example of isolating barriers between sub-populations?
- **Geographical**: mountains, rivers, forests.
- **Ecological**: temperature, pH
- **Behavioural**: courtship mechanisms, breeding times.
86
Describe each stage of speciation.
New **sub-populations are created** by creating an **isolation barrier**.
New **mutations** occur through each **sub-population breeding with their own**, causing new variation.
**Natural selection occurs**, choosing **favourable alleles** that are **advantageous** to each sub-population.
Each **sub-population continues to breed** until they become **so genetically different** that they **can’t interbreed** to create fertile offspring.
You now have two separate species.
