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Edexcel A Biology > TOPIC 4 > Flashcards

TOPIC 4 Flashcards

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1
Q

Define species

A

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

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2
Q

Define habitat

A

A place where an organism lives

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3
Q

Define population

A

A group of interbreeding individuals of the same species found in an area. The various populations in a habitat make up a community.

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4
Q

Define endemic

A

An endemic species is those species that are found only in a limited, restricted, and defined area or habitat, with no traces of its populations in any other part of the world.

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5
Q

Define ecological niche

A

This is the way an organism exploits its environment- so species have a niche when they live in the same habitat and have the same role within the habitat.

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6
Q

What is a behavioral adaptation and give an example of it.

A

A behavioral adaptation is any actions by organisms that help them to survive or reproduce. e.g. when sunflowers turn towards the sun in order to maximise the amount of light received for photosynthesis.

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7
Q

What is a physiological adaptation and give an example of it.

A

Physiological adaptations are features of the inner workings of an organism which help them to survive or reproduce. An example is Danish scurvy grass which allows toleration of high salt concentrations so that it can occupy a new niche.

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8
Q

Anatomical adaptations are…

A

the structures we can see when we observe or dissect an organism

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9
Q

An example of anatomical adaptations is…

A

bumblebees having long tongues which aid them in extracting nectar from flowers

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10
Q

Define co-adaptation.

A

When two organisms become dependent on each other and, so, become more closely and closely adapting to each other.

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11
Q

Define evolution.

A

A change in allele frequency in a population over time

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12
Q

The process of evolution is….

A

1) A population has some naturally occuring genetic variation with new alleles created through mutation
2) A change in the environment causes a change in the selection pressures acting on the population
3) An allele that was previously of no advantage is now favourable
4) Organisms with this allele are more likely to survive and reproduce, and so pass on the allele
5) These offspring are more likely to have the allele so it becomes more common in the population

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13
Q

What are the five fingers of evolution?

A

small population, non-random mating, mutations, gene flow, adaptation

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14
Q

Define gene pool

A

A gene pool consists of all the alleles of all the genes present in a population

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15
Q

The Hardy- Weinberg Equation is…

A

p^2 + 2pq + q^2 = 1

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16
Q

What does p and q represent in the H-W Equation?

A

p^2 is the frequency of homozygous dominant individuals and q^2 is the frequency of homozygous recessive individuals

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17
Q

What does the ability of a population to adapt to new conditions depend upon?

A

The strength of the selection pressure, size of the gene pool and the reproductive rate of the organism

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18
Q

What is speciation?

A

The formation of a new species

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19
Q

The process of speciation is…

A

Geographic isolation: A population of organisms becomes physically separated from other populations, either by a physical barrier (e.g., a mountain range, a body of water) or by other means (e.g., migration to a new habitat). This isolation prevents or restricts gene flow between the populations.

Genetic divergence: Once isolated, the populations experience different environmental conditions and selective pressures, which can lead to genetic differences accumulating over time. Mutations, genetic drift, and natural selection act on the populations’ gene pools, causing genetic divergence.

Reproductive isolation: As genetic differences accumulate, individuals from the two populations may become unable to successfully mate and produce fertile offspring when they come into contact again. This can be due to differences in behavior, mating rituals, anatomy, or genetics. Reproductive barriers prevent gene flow between the populations.

Reinforcement: If reproductive isolation occurs and hybrids between the populations have reduced fitness or reproductive success, natural selection may favor individuals that mate within their own population. This process reinforces the reproductive barriers and further promotes speciation.

Speciation completion: Over time, with continued genetic divergence and reproductive isolation, the populations become distinct enough that they can be classified as separate species. They may have distinct traits, genetic characteristics, and occupy different ecological niches.

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20
Q

What is the binomial system of identification?

A

A unique two-part Latin name where the first part is the genus and second is the species

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21
Q

What is taxonomy?

A

Placing organisms into groups based on shared features

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22
Q

Kevin Please Come Over For Gay Sex

A

Kingdom Phylum Class Order Family Genera Species

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23
Q

What does the kingdom of Animalia contain? What about Plantae? Fungi?

A

Animalia- multicellular eukaryotes that are heterotrophs
Plantae- Multicellular eukaryotes that are autotrophs
Fungi- Multicellular eukaryotes that are heterotrophs that absorb nutrients from decaying matter

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24
Q

What does the kingdom of Protoctista include? What about Prokaryotae?

A

Protoctista- eukaryotes that photosynthesise or feed on organic matter from other sources
Prokaryotae- organisms without membrane bound organelles

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25
Q

What differs Bacteria from Archea according to Woese?

A

Cell wall composition: The cell walls of bacteria and archaea also differ in composition. Bacterial cell walls often contain peptidoglycan, a unique polymer made up of sugars and amino acids. In contrast, archaeal cell walls lack peptidoglycan and have diverse cell wall compositions that can include polysaccharides, proteins, or other substances.
Cell membrane composition: The cell membranes of bacteria and archaea differ in their composition. Bacterial cell membranes typically contain ester-linked phospholipids, while archaeal cell membranes contain ether-linked phospholipids. Additionally, the structure and organization of the lipids in the cell membranes of archaea are different from those in bacteria.
Ribosomal RNA (rRNA) sequences: One of the fundamental differences that Carl Woese used to classify bacteria and archaea into separate domains was the analysis of their rRNA sequences. Bacterial and archaeal rRNA sequences differ significantly, indicating their genetic divergence.

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26
Q

Name the three domains.

A

Bacteria, Eukarya, Archea

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27
Q

The sources of genetic variation during the production of gametes are…

A

Independent assortment, crossing over

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28
Q

The sources of genetic variation during mutation are…

A

Gene point mutations- alterations of the DNA base sequence which may arise during DNA replication
Chromosome mutations- small sections of chromosome may be rearranged during meiosis; they may be inverted, moved during one chromosome to another or even lost altogether.

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29
Q

The sources of genetic variation during fertilization are…

A

Mate selection- Different combination of alleles will come together depending on the two parents
Random fertilisation- Different combinations of alleles will come together in the offspring depending on the sperm and egg involved

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30
Q

What are microfibrils?

A

Bundles of neighbouring cellulose chains

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31
Q

How are microfibrils formed?

A

Microfibrils are formed via hydrogen bonds between -OH groups in neighbouring cellulose chains. They are wound in a helical arrangement around the cell and stuck together with a polysaccharide glue- hemicelluloses and pectins.

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32
Q

Is cellulose a part of the cell wall of plant cells?

A

Yes

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33
Q

Is cellulose made up of 1.4 beta glucose units or 1.6 and 1.4 alpha glucose units?

A

1.4 b-glucose units

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34
Q

Is cellulose a long branched molecule?

A

No, it is unbranched

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35
Q

What is the function of the xylem?

A
  • The function of the xylem is to transport water and aqueous minerals from the roots to the leaves and other areas.
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36
Q

What is the function of the phloem?

A
  • The function of the phloem is to transport sugars and amino acids from the leaves and other photosynthetic parts of the plant to the sinks
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37
Q

What is autolysis and why is it done in the xylem?

A

There is autolysis, or programmed cell death, in order to leave empty cells that can propagate a continuous column of water.

38
Q

What aids the xylem’s tubes in resisting high water pressures?

A
  • Xylem is composed of dead cells which are elongated, hollow tubes which are lignified to resist high water pressures.
39
Q

Is the xylem formed of dead or living cells? Are they hollow tubes?

A
  • Xylem is composed of dead cells which are elongated, hollow tubes
40
Q

What is different about the xylem from the phloem regarding direction of transport?

A
  • The xylem only allows for the transport of water from the roots to the leaves
  • The phloem transports amino acids bidirectionally, to wherever it is needed, using a pressure gradient.
41
Q

Are the companion cells nucleated?

A

Yes

42
Q

The function of the companion cells are…

A

They are dependent on companion cells which are nucleated to produce the energy for the metabolic reactions that the sieve tube elements conduct, via aerobic respiration.

43
Q

The function of sieve cells are…

Why are they perforated?

A

Sieve tube elements transport organic compounds to the sinks of the plant, and are elongated thin walled cells that form long tubes. These elements are perforated to allow for the movement of sugars between adjacent cells.

44
Q

What is the process of transpiration?

A
  • Transpiration-
    1- Water diffuses out through the stoma down a diffusion gradient
    2- Water evaporates from the cell surface
    3- Water is replaced by capillary action within the cell walls
    4- Water is drawn out of the xylem
    5- A continuous column of water is drawn up from the xylem
45
Q

What is the mass transport process in the phloem sieve tube elements?

A

Mass transport in phloem sieve tubes-
1) Solutes are loaded onto the phloem, which increases solute concentration, which draws water into the sieve tube via osmosis from adjacent xylem
2) This increases the hydrostatic pressure inside the lumen of the sieve tube at the loading end
3) At sinks, solutes are unloaded, lowering solute concentration in the sieve tube.
4) Water moves back into the xylem by osmosis lowering the hydrostatic pressure
5) The pressure gradient controls the movement of solute through the phloem

46
Q

What is the plasmodesmata?

A

Narrow fluid filled channels which cross the cell walls, making the cytoplasm of one cell continuous with the cytoplasm of the next. They are usually present in the pits.

47
Q

What do the schlerenchyma fibres do to the vascular bundles?

A

Provide support through their stiffened cell walls.

48
Q

What is cohesion-tension theory (for water)?

A

Cohesive forces between water molecules, which are a result of hydrogen bonding- water in narrow tubes sticks together very strongly.

49
Q

What physiologically occurs when a plant is Mg deficient?

A

unable to produce chlorophyll

50
Q

What are the visible symptoms of Mg deficiency?

A

yellow leaves with reddish brown tints.

51
Q

What are the visible symptoms of Nitrogen deficiency?

A

yellowing leaves, stunted growth

52
Q

What are the physiological implications of a plant having a deficiency in Nitrogen ions?

A

They cannot make amino acids- and so cannot do protein synthesis. They also cannot produce ATP since those contain amino acids.

53
Q

What conditions should seed banks be kept under?

A

Cold, dry conditions in order to prevent germination

54
Q

Are sclerenchyma fibres lignified?

A

Yes

55
Q

Biodiversity is…

A

Biodiversity

= refers to the variance and variability of life on earth

= the number and variety of different organisms found in a specified area

56
Q

Endosymbiosis is…

A

Endosymbiosis = idea that eukaryotic cells are associations of different types of cell which joined together may millions of years ago

57
Q

What are the membranes of eukarya composed of?

A

Membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages

58
Q

What are the membranes of bacteria composed of?

A

Membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages

59
Q

What are some ways to evaluate scientific ideas?

A

Ways to Evaluate scientific ideas

It is peer reviewed by scientists who specialise in the area
Publish in a scientific journal
Other scientists repeat the experiment to hopefully get similar results
Other scientists use the theory to make new predictions and experiments

60
Q

What is the heterozygosity index? What does it show?

A

Heterozygosity index = the proportion of genes which are present in heterozygous form

Number of heterozygotes/
No. of individuals in the population

The higher the number the larger the genetic diversity = more chance of survival

61
Q

Species evenness is…

A

Species evenness = a measure of the relative abundance of the different species making up the richness of an area

How even is the distribution

62
Q

What does it mean for a seed to germinate?

A

Germinate = a seed/ spore begins to grow and put out shoots after a period of dormancy

63
Q

What are tonoplasts?

A

Tonoplasts = a cytoplasmic membrane surrounding the vacuole

64
Q

molecular phylogeny is…

A

Molecular phylogeny = analysis of the structures of many different chemicals and genes to identify the interrelationships b/w groups of organisms

65
Q

What does pectin do in the middle lamella?

A

Pectin acts as a cement in the middle lamella, joining cells together

66
Q

What are the visible symptoms of a lack of calcium in a plant?

A

Stunted growth

67
Q

What are the physiological changes a plant goes through due to Ca 2+ deficiency?

A

Poor cell wall structure: Calcium plays a crucial role in the formation and stability of cell walls. A lack of calcium can lead to weakened cell walls, resulting in reduced structural integrity and increased susceptibility to damage or disease.Calcium pectate is formed.

Increased membrane permeability: Calcium helps regulate membrane permeability and integrity. In the absence of sufficient calcium, cell membranes may become more permeable, leading to the leakage of important ions and metabolites from the cells. This can disrupt cellular functions and affect various physiological processes.

68
Q

What are the phases of drug testing?

A

Drug Testing Phases

Preclinical testing: In this stage, drugs are tested in laboratory and animal models to evaluate their pharmacological properties and potential side effects before proceeding to human trials.

Phase 1 clinical trials: A small group of healthy volunteers is given the drug to assess its safety, dosage, and potential side effects, focusing on its tolerability and pharmacokinetics.

Phase 2 clinical trials: A larger group of patients with the specific condition is involved to evaluate the drug’s effectiveness, optimal dosage, and safety, often involving a control group for comparison.

Phase 3 clinical trials: Conducted on a larger scale with thousands of patients, these trials aim to provide comprehensive data on safety, efficacy, and side effects, further confirming the findings from previous phases.

Regulatory review: The drug manufacturer submits an application to regulatory authorities, who review the clinical data, safety profile, and manufacturing processes to determine whether the drug should be approved for market distribution.

69
Q

What is a double blind trial and what is a placebo?

A

Double Blind Study = neither the patients nor doctors know who has the drug or placebo

Placebos = an inactive substance that looks like the drug but doesn’t do anything

70
Q

Describe the methodology of the deficiency CPAC.

A

Make 5 mixtures: all nutrients, no nitrogen, no magnesium, no calcium and then deionised water→to compare against→liquids
Then split the mixtures up into three test tubes each→for validity→liquids
Measure the masses of 9 germinated seeds of the same plant, e.g mung beans→to use as test subjects→diseases
Then place the seeds’ roots in the mixtures with the seeds out of the liquid using cling film→to represent the ground→glass
Cover the outside of the test tube w/ foil→to prevent light entering and algae growth
Then place all the test tubes near the same light source and leave for two weeks→to allow for plant growth→light = eyes // burn
Every day check if the mixtures need topping up to keep the roots suspended→for plant growth
Carefully remove each plant and blot dry→to not affect mass // for validity
Measure and record the masses of the plants→to compare
Calculate the mean change from the results→for reliability

71
Q

Describe the stages of the antimicrobial properties of plant experiment.

A

Antimicrobial properties of plants experiment
Prepare an agar plate and transfer the bacteria using a sterile pipette→to place in a controlled environment // prevent cross-contamination→its bacteria
Spread the bacteria around the plate using a sterile plastic spreader→for a large SA // to prevent cross-contamination→seriously, its bacteria
Cover the plate w/ lid→to keep it contained→back to the point it’s bacteria
Dry and grind each plant you want to test and soak in ethanol→to use as test subjects // to sterilise→ethanol = slip/ flammable/ eyes
Filter the ethanol off and using sterile forceps dip equally sized sterile absorbent paper in the plant extracts→so the ethanol doesn’t affect it→ethanol
Leave for one hour→to absorb the plant extracts→liquids // glass
Place the discs on the agar plate with another equally sized disc of just ethanol→control group→ethanol
Tape the lid shut, invert and incubate at 25°C for 48 hours→to allow for it to kill the bacteria
Then remove the lid and make 4 radius measurements of each clear zone and calculate an average→to measure and compare→it’s still bacteria
Repeat the experiment and create an average→for reliability and validity

72
Q

What is the purpose of seed banks?

A

Store lots of seeds from different species of plants, esp. endangered ones
Conserve biodiversity and genetic diversity through storing them
If a plant becomes extinct, the seeds can be used to regrow them

73
Q

Chloroplasts are…

A

Chloroplasts are specialized organelles found in plant cells and some algae cells. They are responsible for the process of photosynthesis, which converts light energy into chemical energy in the form of glucose. Chloroplasts have a double membrane structure. The inner membrane encloses a fluid-filled space called the stroma, which contains various enzymes, DNA, and ribosomes. Within the stroma, there are stacks of membrane-bound structures called thylakoids. Stacks of thylakoids are known as grana.

74
Q

Genetic drift is…

A

Genetic drift = the change in frequency of an existing gene variant (allele) in a population due to random sampling of organism

75
Q

Inbreeding depression is…

A

Inbreeding depression refers to the reduction in fitness or overall health of a population or species as a result of increased inbreeding. Inbreeding occurs when closely related individuals, such as siblings or cousins, mate with each other, leading to an increase in the proportion of homozygous alleles in the offspring.

76
Q

Inbreeding depression leads to the harmful effects of…

A

Loss of genetic diversity: Inbreeding reduces the genetic diversity within a population by increasing the frequency of homozygous alleles. This can lead to a higher expression of deleterious or recessive alleles that may have harmful effects on an organism’s fitness and health. In a genetically diverse population, individuals with different alleles can compensate for each other’s weaknesses, but in inbred populations, the reduced genetic diversity limits this compensatory mechanism.

Expression of recessive deleterious alleles: In outbred populations, harmful recessive alleles are often masked by the presence of a dominant, healthy allele. However, when individuals with the same recessive alleles mate and produce offspring, there is an increased chance of these deleterious alleles being inherited in a homozygous state. This can result in the expression of harmful traits, reduced fertility, impaired immune function, and increased susceptibility to diseases or environmental stressors.

77
Q

What is a studbook?

A

Studbooks provide raw data upon which all the breeding plans are based- the scientists’ understanding of genetics shapes the breeding plans themselves. Studbooks are an individual species shows the history and location of all of the captive animals of that species in the places that are co-operating in an overall breeding plan.

78
Q

What is ex situ conservation?

A

Ex situ conservation involves the preservation and protection of biodiversity outside its natural habitat, typically through methods such as captive breeding, seed banks, or botanical gardens.

79
Q

What is in situ conservation?

A

In situ conservation involves the preservation and protection of biodiversity within its natural habitat, focusing on maintaining and managing ecosystems and their native species.

80
Q

Give 3 reasons as to why oil based plastics are not sustainable.

A
  • Burning fossil fuels contributes to a net increase in carbon dioxide concentrations
    -oil reserves will eventually run out
    -Plastics generate non-biodegradable waste, creating major waste disposal problems
81
Q

What does the middle lamella do?

A

Middle lamella join adjacent cell walls together with calcium pectate – adding to the strength of the plant fibres.

82
Q

What is the difference between the primary and secondary cell walls?

A

Composition: The primary cell wall is composed primarily of cellulose, hemicellulose, and pectin. It is relatively thin and flexible, allowing for cell expansion and growth. In contrast, the secondary cell wall is thicker and contains an additional layer of cellulose, along with lignin, which provides rigidity and strength to the cell wall.

Formation: The primary cell wall is formed during cell division and initial cell growth. It is laid down by the cell while it is still expanding. After the primary cell wall is formed, some plant cells, particularly in specialized tissues like xylem and sclerenchyma, can undergo secondary cell wall deposition. The secondary cell wall is synthesized on top of the primary cell wall and provides additional support and protection.

Structure: The primary cell wall is a relatively uniform layer surrounding the cell, allowing for flexibility and elasticity. It consists of interconnected cellulose microfibrils embedded in a matrix of hemicellulose and pectin. In contrast, the secondary cell wall is more complex in structure. It often exhibits distinctive patterns, such as alternating layers or specialized cell wall thickenings. The secondary cell wall contains a higher proportion of cellulose and is reinforced by lignin, providing greater strength and rigidity.

Functions: The primary cell wall is involved in cell expansion, growth, and maintaining cell shape. It allows the cell to stretch and elongate during development. The secondary cell wall, on the other hand, provides mechanical support and protection to the plant cell. It strengthens the cell wall, enabling it to withstand physical stresses, maintain cell integrity, and provide structural support to tissues like xylem and sclerenchyma.

83
Q

Describe the method of the tensile strength experiment.

A

The plant material should be left to soak in a bucket of water for about a week in order for the fibres to be easily extracted (retting).

Once the fibres have been removed, connect them between 2 clamp stands and gradually add mass in the middle until the fibre snaps. Note the mass required to snap the fibre.

Try this again but with individual fibres from different plants and different ways of combining fibres (e.g. twists). You can also compare the tensile strength of the stem to the individual fibres.

84
Q

What are the control variables in the tensile strength experiment?

A

Length of fibre – each fibre should be roughly the same length for a fair comparison

Size of each individual mass – a set of the same weights can be used

85
Q

Describe the process of the experiment where you look at plant stems and plant bundles.

A

Place a small piece of tinned rhubarb on a watch glass.
Use forceps to pick out one or two vascular bundles from this block of tissue and place them on a microscope slide.
Use mounted needles to tease the vascular bundles apart.
Cover the tissue with a drop of methylene blue, and leave for 5 minutes.
Draw off the extra stain with filter paper. Place a drop of dilute glycerol on the fibres and mount under a coverslip.
Examine your preparation under low, medium and high magnification. If the tissues are not separated enough, place your slide on a piece of filter paper, put a filter paper pad on the coverslip and press down with your thumb. This may separate out the tissue. Do not move your coverslip sideways at all. You may need to re-irrigate the slide with glycerol after squashing it. To do this, place a drop of glycerol on the slide next to the coverslip. It will be drawn under the coverslip by capillary action. Blot off any excess and re-examine the slide.
Look for vascular bundles amongst the separated tissues.

86
Q

Why does the pressure flow mechanism of the phloem make it adapted to its function?

A

Pressure Flow Mechanism: The phloem sap movement is primarily driven by a process called the pressure flow mechanism. Sugars and other nutrients are actively loaded into the sieve tube elements at the source, creating a high concentration of solutes. This generates osmotic pressure, causing water to enter the sieve tubes from surrounding tissues. As a result, the sap flows from areas of high pressure (source) to areas of low pressure (sink) through the sieve tubes.

87
Q

explain what a captive breeding programme is

A

A captive breeding program involves breeding and raising endangered or threatened species in controlled environments, such as zoos or specialized facilities, with the aim of increasing their population and eventual release into the wild once genetic diversity increases.

88
Q

The function of the parenchyma fibres is…

A

Parenchyma fibers are specialized plant cells that provide mechanical support to plant tissues. They have thickened cell walls and elongated shapes, which contribute to the strength and rigidity of the plant.

89
Q

Definition of capillary action.

A

Capillary action refers to the ability of water to rise in narrow tubes due to adhesive and cohesive forces.

90
Q

Why are vessel elements perforated?

A

Vessel elements have perforations at their end walls, called perforation plates, which create a direct pathway for water movement between cells.

Edexcel A Biology (2 decks)

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