Alevel Biology Topic 4

Question 1

What is biodiversity?

Answer 1

Compromises every form of life, the genes that give them their specific characteristics, and the ecosystem of which they are part.
- Biodiversity is threatened as never before due to human activity

Question 2

What is endemism?

Answer 2

Species that is uniquely found in only one part of the world and most commonly found in isolated areas.

Question 3

Species richness

Answer 3

Number of different species in a particular area or region

Question 4

Species evenness

Answer 4

Considers each population size in a habitat

Question 5

Heterozygosity index?

Answer 5

Measures the proportion of genes in heterozygous form:

Number of heterozygous/Total population size

Question 6

Diversity Index?

Answer 6

Used to measure diversity at the species level:

N(N-1) / Sum of n(n-1)
N= Number of all organisms in all species total
n= Total number of organisms of each species

The higher the value of D, the greater the biodiversity. Allows for comparison between habitats

Question 7

What is a niche?

Answer 7

The way in which the species exploits it’s envoirnment and the role of an organism in its envoirnment. They become adapted to their environment by the process of natural selection.

Question 8

What are the three forms of adaptations?

Answer 8

Behavioral: A change in behavior of an animal to increase the chance of survival e.g the use of tools to hunt for prey

Physiological: Changes in the internal biochemical functioning of the organism in response to environmental stimulus. E.g changes in metabolic rate for different seasons

Anatomical: Physical or structural adaptations. E.g Cactus plants have spines

Question 9

How does natural selection lead to evolution?

Answer 9

• Natural occurring variation due to a mutation in alleles
• A change in environment results in a change in selection pressure
• Mutated allele may now be more favorable
• organisms will this allele are more likely to survive, reproduce and maybe pass it on to the next generation.
• Allele frequency increase over many generations

Question 10

Evolution and rise of a different species

Answer 10

The change in allele frequency over time. In order for a new species to form, existing population must be reproductively isolated.

Question 11

Hardy wienberg equation

Answer 11

P2 + 2PQ + Q2 = 1
Used to detect changes in allele frequency in a population. Cannot be used if there is a selection pressure, nonrandom mating, mutations, not if the population is small, no movement of organisms .

Question 12

Speciation

Answer 12

Formation of a different species through reproductive isolation

Question 13

What factors affect speciation?

Answer 13

Geographical ( Rivers or mountains)
Ecological (Preferences for habitats)
Seasonal (Mating times)
Mechanical (Changes in reproductive organ)

Question 14

What is the order of classification?

Answer 14

-Three domain system
-Kingdom
-Phylum
-Class
-Order
-Family
-Genus
-Species

Question 15

What are the three domains?

Answer 15

Bacteria, Archaea, Eukaryotes

Question 16

What are the Kingdoms?

Answer 16

-Animalia
-Pantae
-Fungi
-Protoctista
-Prokaryotes

Question 17

Define species

Answer 17

A group of organisms with similar morphology, physiology, and behavior, which can interbreed to produce fertile offspring, and which are reproductively isolated from other species.

Question 18

What is molecular phylogeny and how does it change how we classify things?

Answer 18

It’s the analysis of genetic material to establish evolutionary relationships between organisms. The way in which we classify organisms is constantly changing, and this modern DNA analysis allows us to show relationships between organisms that have not yet been apparent.

Question 19

The case for three domains

Answer 19

-For a long time, it was just accepted that life was either prokaryotes and eukaryotes
-Using molecular Phylogeny, a scientist named Woese found that bacteria (Prokaryotes) and eukaryotes has similarities and presented a new taxonomic group: three domain system called Archaea.

Question 20

How is idea and evidence critically evaluated?

Answer 20

To ensure reliability and validity three keys aspect have to be ensured: Peer review, scientific conferences, dedicated scientific journals.
Before any research is published in must go under peer review where other scientists in the same area of work question is validity, significance, and originality. Then the paper can be published and speeches can be delivered at conferences. Scientists may also repeat the experiment to test for validity

Question 21

All plant cells include the structures in animal cells except…

Answer 21

Centrioles

Question 22

What features can be seen in a plant cell but not an animal cell?

Answer 22

Chloroplasts - Site of photosynthesis
Vacuole - Storage of water and minerals
Tonoplasts - The membrane round the vacuole ton control movement
Cell wall - For strength and support, and protection
Amyloplasts - To store starch
Middle lamella - To stick cells together
Plasmodesma and pits - To allow communication between one cell and other by allowing the connection of cytoplasm

Question 23

What is the sugar polymer found in plant cells?

Answer 23

Cellulose

Question 24

Explain the formation of cellulose and microfibrils? (+Diagram)

Answer 24

-B-Glucose vs A-Glucose
-Flipped over
-Glycosidic bonds
-Straight chain
—————-
-Hydrogen bonds between cellulose chains

Question 25

Compare cellulose with starch?

Answer 25

Starch comes in two forms, Amylopectin and amylose:
Amylose is a straight chain that coils up due to hydrogen bonding of OH molecules. This makes the shape compact so it can store lots of glucose in a small space and is insoluble to little effect on osmotic balance.
Amylopectin are branched starch molecules at (1,6 glycosidic bonds) with many terminal ends which means breakdown can occur more rapid glucose release.
Cellulose is a straight parallel B-glucose polymer meaning this makes the shape compact so it can store lots of glucose in a small space and is insoluble to little effect on osmotic balance.

Question 26

Explain/draw the structure of a cell wall?

Answer 26

Primary cell wall is made up of microfibrils+Cellulose+Hemicellulose+pectins
Middle lamella on top of the primary walk

Question 27

What makes a cell wall useful for its job?

Answer 27

In the primary cell wall, microfibrils are arranged at angles, layered to form a mesh like structure which leads to strength and flexibility
Pectins hold neighboring cells together in the middle lamella
Some specialized cells contain a secondary cell wall inside the primary wall which are long flexible and strong - MAKING IT USEFUL FOR HUMANS AS FIBERS SUCH AS COTTON AND FLAX
The secondary wall may contain lignin and thicker which makes it rigid and waterproof

Question 28

Draw the structure of root and stem crosssection

Answer 28

Vascular bundles on outside in stem with pith in the middle.
In root, vascular bundles in the middle within the pith surrounding it
Vascular bundles have xylem tissue on inside, them phloem, then schlerenchyma fibers

Question 29

What are the different cuts of plant tissues

Answer 29

Transverse and longitudinal

Question 30

Explain the structure and function of xylem vessels.

Answer 30

STRUCTURE:
- Long and hollow with no ends (Allows for easy water transport/flow without need for diffusion)
- Cell wall is thickened with cellulose fibres (Stops the cells from collapsing under sanction)
- Lignified (To make it waterproof and provide structural support)

Function:
-Transport water and mineral ions up the stem through the transpirational stream in transpiration, and also structural support

Question 31

Explain the structure and function of the Phloem

Answer 31

STRUCTURE:
- A living cell
- Reduced cytoplasm (Ease the flow of substances)
- Perforated end walls called sieve plates containing sieve pores
- Lateral pores (Allow movement of water to other phloem tubes and xylem vessels)
- Adjacent to a companion cell (Joined by plasmodesmata so cytoplasms can join to move photosynthetic products. These also have lots of mitochondria to actively transport substances into the phloem tube.

Function:
-Transport of photosynthetic products and plant growth substances up and down the stem and root (Bidirectional), source to sink or Vice-versa

Question 32

Explain the structure and function of the scherenchyma fibers

Answer 32

STRUCTURE:
- Dead cells
- very thick cell wall
- Heavily lignified and secondary thickened but not in spiral form
- very small lumen and maybe absent

Function:
Thickened cell walls provide structural support to the cell

Question 33

What is the cortex of a stem made up of?

Answer 33

Collenchyma and epidermis cells

Question 34

What type of cells in the pith made up of (Packing tissue)

Answer 34

Parenchyma

Question 35

How can plant fibers be exploited by humans?

Answer 35

*Starch - be processed into bioplastics to replace oil plastics (Sustainable)
*They can be burnt to release heat energy
*Lignified plant fibers - Very resistant to chemical and enzyme breakdown
*Cellulose - A structure that does not stretch but is flexible and has great strength

Question 36

What calcium compound can strengthen cell walls?

Answer 36

Calcium pectate

Question 37

Function of the middle llamela in mitosis?

Answer 37

Formed between adjacent cells since they hold the cell walls together. The function is stability and does this through calcium pectate and magnesium pectate

Question 38

Why may clothes made out of starch not be fully sustainable?

Answer 38

Starch is sustainable because it is made from plants and can be regrown, however not 100% so has to use some oil based products

Question 39

Define tensile strength

Answer 39

The pulling force the fiber can withstand before breaking

Question 40

Which organelles in a leaf cell stores starch?

Answer 40

-Chloroplasts
-Amyloplasts

Question 41

What is the role of Starch molecules in a cell?

Answer 41

A store of glucose/energy

Question 42

what is monoculture and it’s effects?

Answer 42

The growing of a single variety of a single crop. This decreases the level of biodiversity in an area because habitats are lost to make way for large fields

Question 43

What are herbicides and it’s effects?

Answer 43

Used to get rid of weeds. Organisms that feed of these weeds are at threat since it causes disturbances in the food chain

Question 44

What are pits?

Answer 44

Narrow areas of the plant cell wall. They have a pit cavity which enables fluid exchange and communication

Question 45

Describe features of chloroplasts

Answer 45

A double membrane, contains RNA, ribosomes, and starch molecules

Question 46

Draw the structure of the chloroplast:

Answer 46

• Thylokoids
• Granums
• Stroma lamaellea
• Stroma
• Outer membrane
• Inner membrane
• Intermembrane space

Question 47

What is the importance of water in plants?

Answer 47

Temperature regulation, mineral transport, photosynthesis, and maintain structural rigidity

Question 48

The effect of the deficiencies in Mg, NO3, Ca, and their role in a plant.

Answer 48

Mg - Poor growth and yellow leaves - Element needed in the production of Chlorophyll

NO3 - Reduced growth - Various molecules such as Chlorophyll, DNA, and proteins

Ca - Wilted and reduced growth - Found in the cell wall for support as calcium pectate

Question 49

Who is William withering and how did he test his drugs on patients?

Answer 49

He was a doctor that found that the extract of foxglove plants can treat dropsy (Now referred to as edema which is the swelling of the heart and kidney). These plants contained digitalis. Too much of this chemical by observation meant patients were poisoned whilst too little has no effect. Therefore by trail and error he came to know the right amount to give patients

Question 50

Explain fully modern drug testing?

Answer 50

*Drug testing is very expensive

Preclinical trials:
- Chemical is tested on animals and human tissue
-Three phase test
*Phase 1: Drug is tested on a group of healthy individuals and side effects are recorded
*Phase 2: The Drug is tested on a large number of patients with placebos and side effects and dosages are calculated
*Phase 3: Thousands of patients are tested on, split into two groups. They are split into previously existing drugs, and the new drug and the comparison is made. Double blind trails also occur.

Placebo: The medicine that looks like the drug, with no side effects, so the patient thinks he is getting better and therefore shows improvement

Double blind trail: Nor the patients or doctors know who has, or hasn’t had the placebo so there is no bias when observing the results

Question 51

What do bacteria need for growth?

Answer 51

Nutrients, Oxygen, and appropriate temperature and PH

Question 52

What is sustainability?

Answer 52

To use resources in a way that doesn’t deplete them and they remain available for future generations to use

Question 53

Walkthrough CPAC 6 - Identifying plant stem tissue

Answer 53

Rough:
- Thin sections, transverse and longitudinal, of plant stem tissue (Preferably dicots stem tissue)
- Stain with methylene blue and wait for 5 minutes
- Add dilute 50% glycerol and mount under a cover slip