Biology Topic 4

Question 1

Define:
Species richness:
Species abundance:

Answer 1

Species richness: the number of different species in an area.

Species abundance: number of each individuals of each species in an area.

Question 2

Measuring species diversity in a habitat?

Answer 2

1. Randomly choose area to sample. E.g. use random number generator to go random number of steps in random direction.
2. Count the number of individuals of each species in sample area. For plants use a quadratic, flying insects a sweepnet, ground insects a pitfall trap, and for aquatic animals a net.
3. Repeat.
4. Use results to calculate biodiversity index.

Question 3

How to calculate heterozygosity index?

Answer 3

Number of heterozygote individuals/ total number of individuals in the population

Question 4

Biodiversity index formula?

Answer 4

D = N(N-1)/ Σn(n-1)

Question 5

Define niche

Answer 5

The role of a species within its habitat, including its interactions with biotic and abiotic factors.

Question 6

Define the 3 different types of adaptation

Answer 6

1. Behavioural adaptations: way an organism acts that increase its chance of survival.
2. Physiological adaptations: processes inside an organism’s body that increase its chance of survival.
3. Anatomical adaptations: structural features of an organisms body that increase its chance of survival.

Question 7

How can adaptations become more common by evolution?

Answer 7

1. Random mutations introduce new alleles into population.
2. Some of the alleles may determine phenotypes that increase an organisms survival chances against selection pressures e.g. disease, competition, predation.
3. Individuals with advantageous characteristics more likely to survive and pass on their advantageous alleles to offspring.
4. Over time, number of individuals with the advantageous alleles increase.
5. Over generations leads to evolution.

Question 8

What is speciation and what are some non-geographic causes of it?

Answer 8

Species= group of similar organisms that can reproduce to give fertile offspring.

Speciation is the development of new species that occurs when populations of the same species become reproductively isolated. The changes in phenotypes prevent breeding, these changes could be:
1.Developing different flowering or mating seasons.
2.Changes to genitalia that prevent successful mating.
3. Development of courtship rituals unattractive to the main population.

Question 9

How can geographic isolation lead to speciation

Answer 9

1. Geographic isolation happens when a physical barrier divided a population of a species. This could be due to flood, volcanic eruption or earthquake.
2. Conditions on either side of barrier will be slightly different e.g. different climate.
3. Different selection pressures mean different characteristics become common due to natural selection.
4. Eventually different populations= genetically distinct.
5. No longer able to reproduce to give fertile offspring, they are now separate species.

Question 10

What are the 2 Hardy-Weinberg equations?

Answer 10

1. p + q = 1
   p= frequency of dominant allele.
   q= frequency of recessive allele.
2. p² + 2(pq) + q²
   p²= frequency of homozygous dominant.
   2(pq)= frequency of heterozygous.
   q²= frequency of homozygous recessive.

Question 11

What are the 5 kingdoms?

Answer 11

Based on general features

Prokaryotae e.g. bacteria: prokaryotes

Proctoctista e.g. algae: eukaryotic, unicellular or very simple multicellular, in water

Fungi e.g. moulds, yeasts, mushrooms: eukaryotic, chitin cell wall, absorb substances from dead organisms.

Plantae e.g. mosses, ferns, flowering plants: eukaryotic, multicellular, cellulose cell wall, able to photosynthesise.

Animalia e.g. reptiles, birds, mammals: eukaryotic, multicellular, no cell walls, heterotrophic

Question 12

What are the 3 domains?

Answer 12

Based on molecular phylogeny which tells us how related species are to each other by looking at DNA and proteins.

Organisms in kingdom prokaryotae are separated into 2 domains, archaea and bacteria.

Organisms from other 4 kingdoms placed in domain of eukaryota.

Prokaryotae reclassified into 2 domains are molecular phylogeny suggested they were more distantly related than once thought.

Question 13

What is a seedbank and what are the advantages and disadvantages of them?

Answer 13

A seedbank stores lots of seeds of lots of different species of plant.
This helps to conserve biodiversity by storing seeds of endangered plants. Also conserves genetic diversity.
The work of seedbanks involve creating the cool, dry conditions needed for storage and testing seeds for viability. Seeds are planted grown and new seeds are harvested and stored.

Advantages: cheaper to store seeds than plants
Larger numbers of seeds can be stored than plants
Less labour required to loom after seeds than plants.
Seeds cab be stored anywhere that is cool and dry.
Seeds are less likely to be damaged by disease, natural disaster, or vandalism than plants.

Disadvantages: testing the seeds for viability can be expensive and time consuming.
Too expensive to store all types of seed and regularly test for viability

It may be difficult to collect seeds from some plants as they grow in remote locations.

Question 14

How do captive breeding programmes help endangered species?

Answer 14

1. Captive breeding programmes involve breeding animals in controlled environments.
2. Endangered species can be bred together in zoos to help increase their numbers.

Problems with captive breeding
1. Some animals can have problems breeding outside their natural habitat, which can be hard to recreate in a zoo.

2. Some people think it’s cruel to keep animals on captivity, even if done to prevent extinction.

Question 15

Reintroduction of organisms from food and seedbanks into the wild

Answer 15

1. Could increase their numbers in the wild, bringing back endangered species from brink of extinction.
2. Could also help organisms that rely on these plants or animals for food or as part of their habitat.
3. Reintroduction also contributes to restoring habitats that have been lost.

Problems:
1. Reintroduced organisms may bring disease to habitats.
2. Reintroduced animals may not behave as they would if they had been raised in the wild e.g. Could have trouble finding food.

Question 16

How can seedbanks and zoos contribute to scientific research?

Answer 16

Seedbanks: scientists can study how plant species can be successfully grown from seeds. This is useful for reintroducing them to the wild.
Seedbanks can be used to grow endangered plants for use in medical research, as new crops, or for new materials. So endangered plants don’t have to be removed from the wild.
Disadvantage= only studying plants from seeds in a seedbank limits data to small, interbred populations.

Zoos: increases knowledge of behaviour, physiology, and nutritional needs of animals.
Zoos can carry out research that’s not possible in wild e.g. reproductive studies.
Disadvantage= captive animals might behave differently to wild animals.

Question 17

How do zoos and seedbanks help to educate people about conserving biodiversity?

Answer 17

1. Zoos let people get close to organisms, increasing their enthusiasm for conservation work.
2. Seedbanks contribute to education by providing training and setting up local seedbanks all round the world.

Question 18

Structure and function of plant cell wall?

Answer 18

Rigid structure that surrounds plant cells. It is mainly made up of the carbohydrate cellulose.

Supports plant cells

Question 19

Middle lamella structure and function?

Answer 19

Outermost layer of plant cell

Acts as an adhesive, sticking adjacent plant cells together. It gives the plant stability.

Question 20

Structure and function of pits?

Answer 20

Regions of the cell wall where the wall is very thin. They’re arranged in pairs- the pit in one cell is lined up with the pit in the adjacent cell.

Question 21

Structure and function of plasmodesmata?

Answer 21

Channels in the cell wall that link adjacent cells.

Allows transport of substances and communication between cells.

Question 22

Structure and function of chloroplasts?

Answer 22

Small, flattened structure. Surrounded by a double membrane, and also has membranes inside called thyloakid membranes. The membranes are stacked to form grana (granum singular). Grana are linked together by lamellae, thin, and flat pieces of thylakoid membrane.

The site where photosynthesis takes place. Some parts of photosynthesis happen in the grana and other parts in the stroma.

Question 23

Structure and function of amyloplasts?

Answer 23

Small organelle enclosed by a membrane. They contain starch granules.

Store starch grains. Also convert starch back to glucose for release when the plant requires it.

Question 24

Structure and function of the vacuole and tonoplast?

Answer 24

The vacuole is a compartment surrounded by a membrane called the tonoplast.

The vacuole contains the cell sap, which is made up of water, enzymes, minerals, and waste products. Vacuoles keep the membrane turgid, which stops the plant wilting. They’re also involved in the breakdown and isolation of unwanted chemicals in the cell. The tonoplast controls what enters and leaves the vacuole.

Question 25

Outline the structure and function of xylem vessels.

Answer 25

1. Transports water and mineral ions up plant, and provide support. 2. Very long tube-like structures formed from dead cells joined end-to-end. 3. Longer than they are wide, hollow lumen (no cytoplasm), and have no end walls. 4. This makes an uninterrupted tube, allowing water and mineral ions to pass through the middle easily. 5. Lignified walls to support the plant. 6. Water and mineral ions move into and out of the vessels through pits in the walls where there is no lignin.

Question 26

Outline structure and function of sclerenchyma fibres?

Answer 26

1. The function of sclerenchyma fibres is to provide support- they are not involved in transport. 2. Like xylem, they're also made up of bundles of dead cells that run vertically up the stem. 3. The cells are longer than they are wide and have hollow lumen. However, unlike xylem contain end walls. 4. Their cell walls are also lignified, but don't contain pits. They contain more cellulose than other plant cells.

Question 27

Outline the structure and function of phloem tissue?

Answer 27

1. Transport organic solutes such as sucrose to where they are needed. This is called translocation. 2. Arranged in tubes. But purely for Transport, not support. 3. Phloem contains sieve tube elements and companion cells. 4. Sieve tube elements are living cells, joined end to end to form sieve tubes. 5. 'Sieve' parts = end walls, which have lots of holes in to allow solutes to pass through. 6. They contain no nucleus, thin cytoplasm and very few organelles. Cytoplasm of adjacent cells is connected through the holes in the sieve plates. 7. Lack of nucleus and other organelles means they can't survive on their own. So there's a companion cell for every sieve tube element. 8. Companion cells carry out living functions for themselves and their sieve cells. E.g provide energy for active transport of solutes.

Question 28

What is the structure of the vascular bundle?

Answer 28

Xylem= innermost Phloem= middle Sclerenchyma= outermost

Question 29

Dissecting and observing plant stems practical?

Answer 29

1. Use a scalpel to cut a cross section of the stem as thinly as possible. 2. Place in water until you use it to stop it from drying out. 3. Stain with toluidine blue and leave for a minute. TBO stains lignin blue-green. 4. Rinse off in water and place each onto a slide. 5. Place your prepared slide under a microscope and adjust the microscope until you get a clear image of your sample. Make a labelled drawing that shows the position of xylem, phloem and sclerenchyma.

Question 30

Structure and function of starch?

Answer 30

Starch = main energy storage material in plants. 1. Cells get energy from glucose. Plants store excess glucose as starch. 2. Starch= mixture of two polysaccharides, amylose and amylopectin. Amylose: long unbranched chain of alpha-glucose. Angles of glyocsidic bonds give it coiled structure. This makes it compact which is good for storage. Amylopectin: long branched chain of alpha-glucose. Side branches allow the enzymes that break down the molecule to get at glycosidic bonds easily- so glucose can be released quickly. 3. Starch is insoluble in water, so it doesn't affect osmotic balance of cell > good for storage.

Question 31

Structure and function of cellulose?

Answer 31

Cellulose= major component of plant cell walls. 1. Made of long unbranched chains of beta-glucose, joined by 1-4 glycosidic bonds. 2. Glycosidic bonds straight, so cellulose chains are straight. 3. Between 50 and 80 cellulose chains are linked together by a large number of of hydrogen bonds to form strong threads called microfibrils. The strong threads mean cellulose provides structural support for cells.

Question 32

Measuring tensile strength of plant fibres practical?

Answer 32

1. Attach fibre to clamp stand and hang weight to other end. 2. Keep adding weights, one at a time, until the fibre breaks. 3. Record mass needed to break the fibre. The higher the mass, the fibre the higher the tensile strength. 4. Repeat with same fibre to calculate a mean. This reduces the effect of random error and makes results more precise. 5. Fibres should always be the same shape. 6. Throughout experiment all other variables e.g. temperature and humidity must be kept constant. 7. Safety= wear goggles and keep area where weights will fall clear to protect feet.

Question 33

How can using plant fibres contribute to sustainability?

Answer 33

1. Ropes and fabrics can be made of plastic, which is made from oil. They can also be made from plant fibres. 2. Making products from plant fibres is more sustainable than making them from oil - less fossil fuels are used and crops can be regrown to maintain supply for future generations. 3. Products made from plant fibres are biodegradable so can be broken down by microbes. 4. Plants are easier to grow and process than extracting and processing oil. So cheaper and easier to do in developing countries.

Question 34

How can starch contribute to sustainability?

Answer 34

1. Starch is found in all plants. 2. Plastics usually made from oil, but some can be made from plant-based materials, like starch. These are called bioplastics. 3. This is more sustainable as crops can be regrown and uses less fossil fuels. 4. Vehicle fuel is also usually made from oil, but you can make fuel from starch. E.g. bioethanol. This is more sustainable.

Question 35

Uses of inorganic ions in plants?

Answer 35

Magnesium ions: needed for chlorophyll- the pigment needed for photosynthesis. Nitrate ions: DNA production, proteins, and chlorophyll. Required for plants growth, fruit production and seed production. Calcium ions: important components in plant cell walls. They're required for plant growth.

Question 36

Investigating antimicrobial properties of plants core practical?

Answer 36

1. Prepare agar plate seeded with bacteria. 2. Prepare extracts for plants you want to use by grinding them and soaking in ethanol. 3. dip filter paper discs into each plant extract using sterile forceps. 4. Dip 1 disc into ethanol as a control. 5. place discs in agar plate, lightly tape so oxygen can still enter, and incubate at 25 C for 48 hours. 6. Area around the extract where bacteria unable to grow= zone of inhibition. 7. calculate zone of inhibition for each extract using pi X radius squared. Repeat experiment to calculate mean zone of inhibition for each extract. The higher the mean zone of inhibition, the more antimicrobial the plant is.

Question 37

Aseptic technique?

Answer 37

close windows and doors to prevent disturbing the air. Regularly disinfect work surfaces. Use sterile equipment, e.g. sterilising forceps with Bunsen burner. Work near bunsen flame as hot air rises so microbes in air will be drawn away from agar plate.

Question 38

William Withering key points?

Answer 38

1. Scientists in 1700s. Discovered that foxglove extract could be used to treat dropsy (swelling brought about by heart failure). This extract contained the drug digitalis. 2. Withering tested patients with different concentrations of digitalis- this became known as his digitalis soup. 3. Too much digitalis poisoned patients, too little had no effect. 4. It was through this crude trial and error that he discovered the right amount to give a patient.

Question 39

Modern drug testing?

Answer 39

Phase 1: testing new drug on small group of healthy individuals. Done to find safe dosage and side effects. Phase 2: If a drug passes phase 1, it will then be tested on a larger group of people ( this time patients) , to see how well drug actually works. Phase 3: drug is compared to existing treatments, with testing on hundred or thousands of patients. One group gets new treatment other group get existing treatment to see if new drug is better.

Question 40

Blind trials and double blind trials?

Answer 40

Placebo= inactive substance that looks like drug but doesn't do anything. Blind trial: patients don't know if drug is real or Placebo. Double blind trial: phase 2 and 3 clinical trials are usually double blind. This is where neither the doctors nor patients know who has received the real drug and who has received the placebo. This reduces bias.