Every AQA A Level Biology Flaschard

Question 1

What is PRIMARY succession?

Answer 1

It is the process where pioneer species, such as lichens, colonize an area adapted to harsh conditions.

Question 2

What happens after pioneer species die in PRIMARY succession?

Answer 2

They are decomposed by microorganisms, adding humus and eventually forming soil.

Question 3

What occurs as the environment becomes suitable for more complex organisms in PRIMARY succession?

Answer 3

Soil becomes richer in minerals, allowing plants like shrubs to survive.

Question 4

What is a climax community?

Answer 4

It is the final stage of succession, a self-sustaining stable community of organisms.

Question 5

What are the stages of SUCCESSION?

Answer 5

A) Pioneer
B) Intermediate
C) Climax
D) Bare rock
E) Lichens
F) Small annual plants & lichens
G) Perennial herbs & grasses
H) Grasses, shrubs & shade-intolerant trees
I) Shade-tolerant trees

Question 6

What is the MARK-RELEASE-RECAPTURE method?

Answer 6

A method used to count fast-moving or hidden animals by capturing, marking, and releasing them.

Question 7

Why is the MARK-RELEASE-RECAPTURE method used?

Answer 7

To count fast-moving or hidden animals.

Question 8

What is CONSERVATION?

Answer 8

The management of the earth’s resources, typically involving the management of succession.

Question 9

Give an example of CONSERVATION.

Answer 9

Controlled burning of land is done to stop the formation of a climax community.

Question 10

What is SECONDARY succession?

Answer 10

Succession that occurs in a previously colonized area where an existing community has been cleared.

Question 11

What events can trigger SECONDARY succession?

Answer 11

Events like forest fires.

Question 12

What is a RECESSIVE allele?

Answer 12

A characteristic expressed only if there is no dominant allele present.

Question 13

What is required for a RECESSIVE allele to be expressed?

Answer 13

Two recessive alleles (homozygous recessive) must be present.

Question 14

What is a CODOMINANT allele?

Answer 14

Both alleles are expressed equally, contributing to the phenotype.

Question 15

What does PURE BREEDING mean?

Answer 15

A homozygous pair of alleles.

Question 16

Define ALLELE.

Answer 16

An alternative form of a gene.

Question 17

What is meant by HOMOZYGOUS?

Answer 17

Both alleles are dominant or both alleles are recessive.

Question 18

What is meant by HETEROZYGOUS?

Answer 18

One allele is dominant and the other allele is recessive.

Question 19

Describe the structure of bony fish gills.

Answer 19

They have 4 pairs of gills supported by arches, with multiple projections called gill filaments.

Question 20

What are lamellae in bony fish gills?

Answer 20

Structures on gill filaments that help with gas exchange.

Question 21

What points are assumed so the Hardy-Weinberg equation can be used?

Answer 21

No mutations occur to create new alleles. There is no movement of alleles into/out of the population by migration. The population is large. There is no selection = every allele has an equal chance of being passed to the next generation. Mating is random.

Question 22

What is INTRAspecific competition and give examples of factors that affect it?

Answer 22

Factors that members of the SAME species compete for.

FACTORS = food, water, mates, shelter, minerals and light.

Question 23

Describe an example of INTRAspecific competition.

Answer 23

Male robins maintain a large territory to support their families but in winter when food is short, they move to other males’ territories to obtain enough food to survive.

Question 24

What is INTERspecific competition and give examples of factors that affect it?

Answer 24

When members of DIFFERENT species compete with one another for the same resources. This occurs most commonly when different species occupy the same niche.

Question 25

Describe an example of INTERspecific competition.

Answer 25

Red and grey squirrels in the UK.

Question 26

Define PREDATION.

Answer 26

When one species (the prey) is caught and eaten by another species (the predator).

Question 27

Label the structure of the synapse.

Answer 27

A) Presynaptic neurone B) Ca2+ C) Synaptic vesicle D) Calcium ion channel E) Sodium ion channel F) Synaptic neurone G) Na+ H) Synaptic cleft I) Receptor J) Neurotransmitter K) Synaptic knob.

Question 28

Describe the transmission across a CHOLINERGIC synapse.

Answer 28

AP opens voltage-gated Ca2+ channels in synaptic knob. Ca2+ enters tissue fluid from synaptic cleft -> pre-synaptic cell. Ca2+ causes vesicles of acetylcholine (Ac) to fuse with pre membrane. Ac is released by exocytosis and diffuses by facilitated diffusion = binds to receptors on post membrane. Na+ channels open = depolarisation of post membrane & threshold of -50mV is reached -> AP.

Question 29

What are the 2 types of synapses?

Answer 29

Excitatory and inhibitory.

Question 30

What do EXCITATORY synapses do?

Answer 30

Induce an AP in post-synaptic membrane.

EXAMPLE = cholinergic synapse.

Question 31

What do INHIBITORY synapses do?

Answer 31

Make an AP less likely to occur = one neurone can inhibit an AP in the next neurone.

EXAMPLE = GABA.

Question 32

What are some important roles of the synapse?

Answer 32

Allow flow of information from one neurone to another = unidirectional. Allow next neurone to be excited or inhibited. Protect nervous system from over-stimulation. Filters out low-level stimuli. Forms the physical basis for memory/learning.

Question 33

What is SUMMATION and what does it allow?

Answer 33

Low frequency APs will often release insufficient amounts of neurotransmitters to exceed the threshold in post-synaptic neurone. Allows AP to be generated by building up neurotransmitters in the synapse.

Question 34

What are the 2 types of summation?

Answer 34

Spatial and temporal.

Question 35

What is synaptic INHIBITION?

Answer 35

Cl- ions on postsynaptic membrane open = ions flood into neurone. Axon becomes HYPERPOLARISED = becomes harder for an AP to be generated.

Question 36

What is summation and inhibition of synapses described as?

Answer 36

They work antagonistically at the SAME synapse.

Question 37

What are organs? (give examples)

Answer 37

A grouping of tissues into a distinct structure that perform a specialised function.

Example: the heart.

Question 38

What is a NEUROMUSCULAR junction?

Answer 38

A type of effector in the muscles that releases neurotransmitters.

Question 39

Label the structure of a NEUROMUSCULAR junction.

Answer 39

A) AP B) Motor neurone axon C) Synaptic cleft D) Pre-synaptic membrane E) Sarcolemma F) Mitochondrion G) Skeletal muscle H) Myofibril I) Nucleus J) Sarcoplasm K) Synaptic vesicles containing acetylcholine L) Synaptic knob.

Question 40

Describe the effects of EXCITATORY drugs on the synapse.

Answer 40

Some will stimulate the release of more neurotransmitters. This generates an AP faster because the threshold is reached quicker.

EXAMPLE: caffeine stimulates the release of more Ca2+ ion.

Question 41

Describe SPATIAL summation.

Answer 41

Multiple presynaptic neurones charge the same synaptic cleft. Together they can release enough neurotransmitters to create an AP.

Question 42

Describe TEMPORAL summation.

Answer 42

Single presynaptic neurone releases neurotransmitters over a short time. Total amount released increases threshold value = AP sent in presynaptic neurone.

Question 43

Compare & contrast synapses with neuromuscular junctions (NMJ) [5].

Answer 43

SIMILARITIES: Both are stimulated by AP/cause depolarisation of post membrane. Both release acetylcholine (neurotransmitters). Unidirectional with receptors present on post membrane. Use calcium ions to release neurotransmitters.

DIFFERENCES: Synapse between neurones & NMJ between motor neurones and muscles. Information between neurones & cause muscle contractions. Synapses can be excitatory/inhibitory & NMJ only excitatory. Synapses generate another AP & NMJ are at end of AP (moves AP to muscles for contraction).

Question 44

Describe what is meant by a PREDATOR-PREY relationship.

Answer 44

The populations of the predator will both affect one another.

Question 45

What is included in an ECOSYSTEM?

Answer 45

The organisms living in a particular area = the community. The non-living elements of that particular environment. Controlled by biotic (living) and abiotic (non-living) factors.

Question 46

Describe PREDATION.

Answer 46

When the prey is eaten by predator = population of prey falls. Population of predator grows = more prey is consumed. Population of prey reduces = increase competition for prey between predators. Lack of food for predators = population falls and less prey is eaten. Allows the population of the prey to recover and cycle occurs over and over again.

Question 47

How can the size of a population be ESTIMATED?

Answer 47

Using randomly placed quadrats or quadrats placed along a belt transect for SLOW-MOVING or NON-MOTILE organisms.

Question 48

How can the ABUNDANCE of different species be measured?

Answer 48

Percentage cover -> suitable for plants or algae whose individual numbers are difficult to count. Frequency -> the number of times an organism appears in the sampling area and is expressed as a decimal or percentage.

Question 49

What are the assumptions that need to be made when using the MARK-RELEASE-RECAPTURE method?

Answer 49

The proportion of marked to unmarked in SECOND sample is the same as proportion in the population as a whole. The marked individuals released from FIRST are distributed evenly amongst the rest of the population and have sufficient time to do so. There is a definite boundary to the population so no migration in or emigration out. There are few (if any) births and deaths. The method of marking is not toxic and doesn’t reduce chance of survival. The marks don’t rub off during investigation.

Question 50

Define SUCCESSION.

Answer 50

The change of one community of organisms into the other shows that ecosystems are very dynamic.