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Biology AS Level > Topic 4 - Biodiversity And Natural Resources > Flashcards

Topic 4 - Biodiversity And Natural Resources Flashcards

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1
Q

What is a species?

A

A species is a group of organisms with similar morphology, physiology and behaviour, which can interbreed to produce fertile offspring, and which are reproductively isolated (in place, time or behaviour) from other species.

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2
Q

Are horses and donkeys the same species?

A

No, horses and Donkeys are separate species because although they can produce a mule, that mule is infertile. This means they are closely related, they remain distant.

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3
Q

What’s the importance of DNA analysis?

A

It is increasingly used in the identification of species. It can help us to tell whether two slightly different species are one or two.

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4
Q

What are being developed to be able to identify species without looking at there phenotypes?

A

DNA barcodes

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5
Q

What cannot DNA analysis tell us?

A

Whether two populations can breed together to produce fertile offspring.

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6
Q

What are habitats?

A

The particular place where a community of organisms is found.

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7
Q

What is a population?

A

A group of individuals belonging to one species. Members of a population are generally found in one place at a particular time and are also able to breed with one another.

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8
Q

What is a community?

A

All the living organisms - animals, plants and microorganisms -found in a particular place at a particular time.

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9
Q

What does an organisms environment provide?

A

All the essential resources, such as energy, raw materials, a place to live and a mate.

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10
Q

What is competition?

A

A relationship between different organisms which require the same resources. Competition occurs between different species. Competition may also occur between organisms of the same species, e.g. Seedlings of a particular species of a plant compete with each other when they are growing close together.

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11
Q

What is a niche?

A

The way an organism exploits (uses) its environment.

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12
Q

All the species using a habitat have different ….

A

Niches.

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13
Q

If two species live in the same habitat - the same food source, the same time of feeding, the same shelter site - what do they occupy?

A

The same niche and they will compete directly with each other.

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14
Q

What are adaptations?

A

Features that enable an organism to survive. Adaptations can be classified as behavioural, physiological or anatomical.

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15
Q

What are behavioural adaptations?

A

Any actions by an organism that help them to survive or reproduce.

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16
Q

What are physiological adaptations?

A

Internal workings of an organism that help them to survive or reproduce.

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17
Q

What are anatomical adaptations?

A

The structures we can see when we observe or dissect an organism.

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18
Q

What are co-adaptations? Give an example

A

When two organisms become dependent on one another. Plant and its pollinator.

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19
Q

What is natural selection?

A

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

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20
Q

What is natural selection also known as?

A

Survival of the fittest

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21
Q

What is evolution?

A

A change in form, behavioural and physiological, over generations. (Change in the frequency of alleles in the population)

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22
Q

Describe evolution by natural selection (6 points)

A

1) A population has some naturally occurring genetic variation with new alleles created through mutations.
2) There is competition for resources which means it is insufficient for all individuals to survive.
3) Individuals that are better adapted and have the advantageous allele are more likely to survive and reproduce.
4) The offspring that has the beneficial characteristic/allele.
5) The allele for the beneficial characteristic becomes more common and reproduce.
6) This process repeats itself over every population leading to better adaptations.

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23
Q

Regarding evolution, what happens when the environmnet stays stable?

A

The organisms may simply become better and better adapted to their existing niches.

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24
Q

What is a gene pool?

A

All the alleles of all the genes present in a population.

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25
Q

Why do we look at gene pools?

A

The concept of a gene pool is useful when thinking about biodiversity and adaptability of any species.

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26
Q

If a population has a big gene pool, what does this mean?

A

A population with a bigger gene pool has more different alleles of each gene and therefore there is more biodiversity. They are more likely to possess alleles that will allow them to survive. The frequency of those alleles will change overtime due to natural selection.

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27
Q

What is the equation for the relationship between two frequencies?

A

P + q = 1

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28
Q

What is the Hardy-Weinberg Equation?

A

p2 + 2pq + q2 = 1

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29
Q

In the hardy-Weinberg equation, what does the p2 stand for?

A

The frequency of homozygous dominant individuals.

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30
Q

In the hardy-Weinberg equation, what does the 2pq stand for?

A

The frequency of heterozygous individuals

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31
Q

In the hardy-Weinberg equation, what does the q2 stand for?

A

Frequency of homozygous recessive individuals.

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32
Q

What does it mean to being adaptable?

A

The ability of the population to adapt to new conditions.

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33
Q

What does being adaptable depend on?

A
  • The strength of selection pressure
  • The size of the gene pool
  • The reproductive rate of an organism
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34
Q

Can a population be perfect? Why?

A

No! When an environment changes, there is a time lag before a population can adapt by natural selection, so organisms are always playing a game of evolutionary catch up. Even in stable environments, mutations occur all the time. This makes a population less well adapted to its surroundings.

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35
Q

What is the benefit of being closely to perfectly adapted?

A

Being close to perfect means that an organism is adapted to a specialised niche which helps avoid competition.

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36
Q

For a new species to form what needs to occur?

A

Reproductive isolation needs to occur of a group of individuals from the rest of the species.

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37
Q

What does reproductive isolation lead to?

A

Normally a geographical feature which prevents a group of individuals from breeding. Overtime two groups become less like each other by responding to different selection pressures and as random mutations accumulate. Speciation occurs.

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38
Q

What is speciation?

A

When there are two new species that cannot breed or communicate.

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39
Q

What is biodiversity?

A

The range of organisms found in a particular place.

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40
Q

Describe a place that has a low biodiversity?

A

Deserts have a low biodiversity because the climate is harsh and a few species are adapted to living in it.

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41
Q

Describe a place that has a high biodiversity?

A

Tropical forests and coral reefs, the biodiversity is high.

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42
Q

What does biodiversity also refer to?

A

The diversity within a species.

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43
Q

What is binomial system made up of?

A

Two parts:

  • Genus - Shared by closely related species -> horses and zebras (Equus)
  • Defines the particular species in the genus.
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44
Q

How are organism sorted and grouped?

A

Organisms are placed into groups based on shared features (classification / taxonomy)

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45
Q

Who created the first classification system and how were the organisms classified?

A

Linnaeus created the first classification system, grouping organisms according to visible similarities and differences.

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46
Q

What is the hierarchy order?

A
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
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47
Q

What are the five kingdoms?

A
  • Animalia
  • Plantae
  • Fungi
  • Protocista
  • Prokaryotae
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48
Q

What are the anamalia?

A

Multicellular eukaryotes that are heterotrophs

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49
Q

What are the plantae?

A

Multicellular eukaryotes that are all autotrophs

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50
Q

What are fungi?

A

Multicellular eukaryotes that are heterotrophs that absorb nutrients from decaying matter after external digestion.

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51
Q

What are protocista?

A

Eukaryotes that photosynthesise or feed on organic matter from other sources but are not included in the other kingdoms; includes single-celled protozoa, such as amoeba and algae. (Both autotrophic and heterotrophic forms exist).

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52
Q

What are prokaryotae?

A

Prokaryotic organisms; includes bacteria

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53
Q

Who was Carl Woese?

A

He pioneered RNA sequencing of bacteria -> constructed phylogenies of groups of bacteria. He noticed that Methanogens, completely lacked the sequence characteristic of bacteria. Unlike other bacteria, methanogens had no peptidoglycans. Overall, the RNA sequence showed up completely different from all other bacteria. Therefore a new group was identified, the archaea.

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54
Q

What are archaea?

A

A third branch of life along the prokaryotes and eukaryotes. They are some of the earliest forms of life, existing before oxygen. They survive in extreme anaerobic environments.

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55
Q

What are the three domains?

A
  • Bacteria
  • Archaea
  • Eukaryotes
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56
Q

What is the diagram based on the three domains called?

A

The phylogenetic tree

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57
Q

The phylogenetic tree based on the three domains contains…

A

The organisms in each of the three domains which contain RNA sequences that are unique to their domain.

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58
Q

Are archaea closer to bacteria or eukaryotes?

A

The archaea have a closer evolutionary relationship to eukaryotes.

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59
Q

Give an example of when DNA analysis does not follow Linnaean classifications?

A

Birds and reptiles are placed in separate class yet DNA analysis puts birds with turtles, snakes and crocodiles -> supported by fossil evidence as they descended from dinosaurs.

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60
Q

What is convergent evolution?

A

Unrelated organisms evolving a similar appearance as they adapt to the same conditions.

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61
Q

Give an example of an convergent evolution?

A

Sharks and dolphins

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62
Q

why do we classify organisms?

A

Classification when used in partnership with genetic analysis, enables us to look at evolutionary relationships.

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63
Q

What is biodiversity within a species?

A

Individuals within a species differ from one another - they show variation.

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64
Q

What is genetic diversity?

A

In all organisms that reproduce sexually, every individual has a unique combination of alleles.

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65
Q

What does genetic diversity allow?

A

Th population to adapt to changing conditions.

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66
Q

When there is a greater variety in genotypes, is the population more or less genetically diverse?

A

More

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67
Q

What are the sources of genetic variation?

A
  • Mutations in genes and chromosomes
  • Independent assortment and crossing over
  • Mate selection
  • Random fertilisation
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68
Q

How can mutations cause genetics variation?

A
  • Chromosomes - Small sections of chromosome may be rearranged during meiosis ->inverted, moved from one to the other or lost.
  • Gene - Alterations on the DNA base sequence -> occur during DNA replication or more rarely at other stages of the cell cycle.
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69
Q

How can independent assortment and crossing over at the preparation for sexual reproduction cause genetic variation?

A

Independent assortment - Each homologous pair of chromosomes is sorted independently of the other during meiosis and the process is random.
Crossing over - New combinations of alleles result when pieces of genetic material are exchanged between homologous chromosomes during meiosis.

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70
Q

How can fertilisation cause genetic variation?

A
  • Mate selection - Different combinations of alleles will come together in the offspring depending on which two parents mate together.
  • Random fertilisation - Different combinations of alleles will come together depending on the sperm and the egg involved.
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71
Q

Genetic diversity may be visible, How?

A

Genetic difference within species show up clearly in the external phenotypes. However much genetic variation has no visible effect on phenotype.

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72
Q

What is species richness?

A

Counting the number species present in a given habitat.

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73
Q

What is species evenness?

A

Takes into consideration the population size of each species.

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74
Q

A community in which most of the species have a similar abundance is said to have a … evenness

A

A high evenness with no single species dominating the community.

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75
Q

What does the diversity index calculate?

A

A quantitive score for biodiversity that takes account of both richness and evenness.

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76
Q

What is the equation for the diversity index?

A

D= N(N-1) / E n(n-1)

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77
Q

What is a biodiversity hotspot?

A

Areas of particularly high biodiversity.

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78
Q

How to measure genetic diversity within a species?

A

-DNA sequencing to determine the bases in a segment of DNA and thus to determine which alleles are present.
-DNA can be cut into fragments and then separated using electrophoresis.
The genes from a grouo of individuals are sampled and the alleles present in this sample are recorded -> more alleles -> more biodiversity

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79
Q

What do conservationist biologists use?

A

Genetic diversity indices to compare different populations when deciding which populations need to be conserved.

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80
Q

What does biotic mean?

A

Living

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81
Q

What does abiotic mean?

A

non-living

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82
Q

What are the three strands of biodiversity?

A
  • Species
  • Genetic
  • Habitat
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83
Q

Put niche, habitat, community, ecosystem, population and species in order of size (largest to smallest)

A 
Ecosystem 
Habitat
Community 
Niche
Species 
Population
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84
Q

What is an ecosystem?

A

An area that contains many habitats

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85
Q

What is competitive exclusion?

A

When two species occupy the same nisei he leading to one dying out because of increased competition.

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86
Q

What three basic principles do plants use to build strong structures?

A

1) They produce strong cell walls out of cellulose, a polymer made from sugar molecules.
2) They build columns and tubes from specialised cells.
3) They stiffen some of these specialised cells with another polymer called lignin.

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87
Q

What are the two main differences between a plant and animal cell?

A
  • The plant cell has a rigid cell wall

- The plant cell contains chloroplast.

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88
Q

List the organelles and different structures of a plant cell.

A
  • Ribosomes
  • Vacuolar membrane (tonoplast)
  • Chloroplast
  • Smooth endoplasmic reticulum
  • pit
  • plasmodesma
  • middle lamella
  • rough endoplasmic reticulum
  • chromatin
  • nucleolus
  • nuclear envelope
  • mitochondrion
  • cell surface membrane
  • cell wall
  • amyloplast containing starch grains
  • Golgi apparatus
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89
Q

What is the parenchyma?

A

Relatively unspecialised tissue found in plants. Parenchyma cells have thin cellulose cell walls and living contents. These cells are very important in providing support in young stems; they can photosynthesise and they can store substances such as starch.

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90
Q

What is cellulose?

A

A polysaccharide which is an important component of plant cell walls. A molecule of cellulose consists of a long straight chain of beta-glucose molecules joined by glycosidic bonds. Hydrogen bonds form between neighbouring chains. These bonds hold the cellulose molecules together in bundles called microfibrils.

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91
Q

Cellulose is a … of glucose

A

Polymer

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92
Q

Is cellulose made up of alpha-glucose or beta-glucose? What does the other form of glucose make up?

A

Beta-glucose makes cellulose whereas alpha-glucose makes starch.

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93
Q

What is the difference in structure between an alpha-glucose and a beta-glucose?

A

The -OH on the fourth glucose of the alpha-glucose is swapped with the H on the beta-glucose. Therefore, the beta-glucose’s first carbon is OH rather than H.

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94
Q

Describe how beta-glucose molecules join to form cellulose.

A

A condensation reaction between the -OH group on the first carbon of the one glucose and the -OH on the fourth carbon of the adjacent glucose links the two glucose molecules.

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95
Q

In cellulose what are the bonds formed between the glucose molecules?

A

1,4 glycosidic bonds

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96
Q

Why is cellulose a long and unbranched molecule?

A

There are no 1,6 glycosidic bonds that occur in starch as these provide the branches.

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97
Q

What is the shape of a cellulose molecules?

A

They are long unbranched molecules.

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98
Q

What forms between the neighbouring cellulose chains?

A

Hydrogen bonds

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99
Q

What do the cellulose chains joined together make?

A

Bundles called microfibrils

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100
Q

Which bonds are stronger the glycosidic or hydrogen bonds?

A

Glycosidic bonds are stronger but the high number of hydrogen bonds in the microfibrils produces a strong structure.

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101
Q

How are the microfibrils arranged?

A

They are wound in a helical arrangement around the cell.

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102
Q

What sticks and holds the microfibrils together?

A

A polysaccharide glue

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103
Q

What is the polysaccharide glue that holds the microfibrils together composed of?

A

It is composed of short, branched polysaccharides known as hemicelluloses and pectins.

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104
Q

What do the polysaccharides in the glue do?

A

These short polysaccharides bind both to the surface of the cellulose and to each other, and hold the cellulose microfibrils together.

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105
Q

What are hemicelluloses?

A

Polysaccharides that have molecules made up of short chains of various sugars. They are important in plant cell walls where they help to bind cellulose microfibrils together.

106
Q

What are pectins?

A

A structural carbohydrate found in plant cell walls. Pectin consists of a mixture of polysaccharides, depending on its source. The majority of the structure is formed of repeating units of galacturonic acid. Pectins combine with calcium ions to form calcium pectates. Calcium pectates are found in and between plant cell walls where they help to cement cellulose fibres together.

107
Q

What makes the structure of the wall strong and flexible?

A

The microfibrils are laid down at different angles.

108
Q

What are the plasmodesmata?

A

Small fluid-filled channels through the cell walls of plant cells. Plasmodesmata allow dissolved molecules such as mineral ions to pass directly from the cytoplasm of one cell to the cytoplasm of the next. These molecules do not have to pass through cell membranes or cell walls.

109
Q

How do pits form?

A

At some places the cell wall is thin because only the first layer of cellulose is deposited. The result is a pit in the cell wall.

110
Q

Where are the plasmodesmata often located?

A

In pits

111
Q

What are the three specialised types of cells in plants?

A
  • Xylem vessels
  • sclerenchyma fibres
  • phloem sieve tube cells
112
Q

What is the function of the xylem vessels?

A

These form tubes for transport of water and minerals, and their stiffened cell walls help support the plant.

113
Q

What is the function of the sclerenchyma fibres?

A

Columns of these cells with their stiffened cell walls also provide support.

114
Q

What is the function of the phloem sieve tube cells?

A

These form long tubes for transport of organic solutes, such as sugars and amino acids. They do not have a role in supporting the plant upright.

115
Q

What are the three types of basic tissue found within plants?

A
  • Dermal tissue (epidermis)
  • Vascular tissue
  • Ground tissue
116
Q

What is the vascular tissue?

A

One of the three main types of tissue found in a plant. Vascular tissue consists of xylem and phloem. Xylem transports water and mineral ions from the roots, up through the stem to the leaves. Phloem transport the products of photosynthesis from the leaves to other parts of the plant.

117
Q

Which direction is water and inorganic ions carried in the xylem vessels?

A

Up through the stem

118
Q

Which direction are the products of photosynthesis transported in the phloem?

A

Up and down the plant

119
Q

In a vascular bundle from inside to out name the order of the three specialised cells.

A

Xylem vessels, phloem sieve tube cells, Sclerenchyma fibres

120
Q

What is the collenchyma tissue?

A

A type of supporting tissue found in plants. Collenchyma cells are slightly elongated and have their cell walls strengthened with extra cellulose at the corners.

121
Q

What are the xylem vessels made up of?

A

They are made up of large cells and thick cell walls.

122
Q

What is lignin?

A

A polymer found in some plant cell walls. The main component of plant cell walls is cellulose. In sclerenchyma and xylem, the cellulose is impregnated with lignin. Lignin makes the walls stronger and more able to resist the forces on them. However, it also prevents water and salts getting through. As a result of being lignified the cell dies.

123
Q

What is autolysis?

A

Self-destruction of cells.

124
Q

When does autolysis occur?

A

When cells become lignified, the tonoplast breaks down and there is autolysis of the cell contents.

125
Q

What happens during autolysis?

A

The cells organelles, cytoplasm and cell surface membrane are broken down by the action of enzymes and are lost, leaving dead empty cells that form a tube.

126
Q

Why are xylem vessels so strong?

A

The cellulose microfibrils and lignin in the cell walls of the xylem vessels give the tubes great strength and hence a role in supporting the plant.

127
Q

How is water transported through xylem vessels?

A

1) Water vapour diffuses out through the stoma down a diffusion gradient.
2) Water evaporates from the surfaces of cells lining the substomatal cavity.
3) Water replaced by means of capillary action within the cell walls.
4) Water is drawn out of the xylem.
5) A continuous column of water is drawn up through the xylem.

128
Q

What provides the force that causes water to be transported up the xylem vessels?

A

It is the evaporation of water from the cells in the substomatal cavities of the leaves that provides the force needed to draw water up the plant.

129
Q

What does it mean by the “water is replaced by capillary action”?

A

The minute channels between the cellulose have the ability to draw water up by capillary action, which is caused by the surface tension between the water and the capillary walls. As water evaporates from the surfaces of the cell walls within the leaf, it is replaced by means of capillary action within the cell walls. This draws more water to the cell surfaces. The thousands of minute capillary-like channels in the cell walls inside the leaves produce a massive pull on the water behind them. This pull is thought to be sufficient enough to draw water from the xylem vessels and up the whole stem of the plant. Water moves up the xylem vessels and through the cell walls within the leaf in a continuous stream.

130
Q

What is a transpiration stream?

A

The stream of water passing through a plant.

131
Q

What is transpiration?

A

Evaporation of water from the leaves of plants. During transpiration, water evaporates from the surfaces of the cells lining the substomatal cavities and diffuses out through the stomata.

132
Q

Where does the energy come from that allows the water to move through the plant?

A

The energy from moving water comes from the sun, which heats and evaporates water from the cells lining the substomatal cavity.

133
Q

What keeps the xylem vessels from collapsing in on themselves?

A

The lignification

134
Q

Why does the xylem vessel not break when pulled?

A

It is because of the cohesive forces between the water molecules, which are a results of hydrogen bonding (water in narrow tubes sticks together very strongly)

135
Q

What is cohesion?

A

A force resulting from attraction between molecules of the same substance. Water molecules stick to each other by cohesion. As a result, transpiration pulls a continuous, unbroken water column up through the xylem in a plant stem.

136
Q

What is the cohesion-tension theory?

A

A theory explaining the movement of water through the xylem of a plant from the roots to the leaves. Water molecules stick to each other by cohesion. As a result, transpiration pulls a continuous, unbroken water column up through the xylem. This water column is under tension as a result of being pulled up by transpiration and down by gravity.

137
Q

What is a mass flow system?

A

A system that transports substances in bulk from one part of an organism to another. Large organisms cannot rely on diffusion alone to meet their needs. It is too slow. They need mass flow systems which move substances rapidly over long distances. Examples of mass flow systems are the xylem in a flowering plant and the blood system in an animal.

138
Q

What do plants need nitrogen ions for?

A

Nitrate ions are needed by plants in order to make amino acids.

139
Q

If inorganic ions are not absorbed in sufficient amounts, what will happen?

A

The plant will show deficiency symptoms.

140
Q

What does a lack of magnesium in plants lead to?

A

The plants is unable to make chlorophyll

141
Q

What does a lack of calcium in plants lead to?

A

It causes stunted growth

142
Q

Hydrogen bonds between water molecules is known as?

A

Cohesion

143
Q

Hydrogen bonds between water molecules and the cell wall is known as?

A

Adhesion

144
Q

What is surface tension at water surfaces partly caused by?

A

The cohesive forces between water molecules.

145
Q

Why is it important that water has solvent properties?

A

It allows substances which have dissolved in the water to be transported around the plants through the xylem and phloem.

146
Q

Why is the high specific heat capacity of water important to organisms?

A

A large input of energy causes only a small increase in temperature, so water warms up and cools down slowly. This is extremely useful for organisms, helping them to avoid rapid changes in their internal temperature and enabling many of them to maintain a fairly steady temperature even when the temperature of their surroundings varies considerably.

147
Q

What happens as liquid cools and freezes?

A

Water expands as it freezes. As liquid water cools, the molecules slow down, enabling the maximum number of hydrogen bonds to form between the water molecules. These hydrogen bonds hold the water molecules further part than in liquid water, making ice less dense than liquid water.

148
Q

Apart from the xylem and phloem transporting different substances what is another difference about the cells?

A

Unlike xylem vessels, phloem sieve tubes remain alive.

149
Q

What happens to the organelles within a phloem sieve tube?

A

The nucleus and most cell contents disintegrate during development, with only a few organelles remaining in the thin layer of cytoplasm close to the cell wall. This leaves most of the cell as a liquid filled space, called the lumen.

150
Q

What do the end walls of phloem sieve tubes have and why?

A

The end of the walls of each sieve tube cell contains holes that are aligned with those of the neighbouring cell to allow transfer of material between the fluid filled lumen of adjacent cells.

151
Q

What are the sieve plates?

A

The perforated end walls.

152
Q

What is translocation?

A

The transport of organic molecules within the phloem.

153
Q

What are the main substances transported by the phloem?

A

Sugars (usually sucrose) and amino acids

154
Q

Where does fluid in the lumen move?

A

Along the sieve tube

155
Q

What are the amino acids used for in plants?

A

Growth

156
Q

What are the sugars used for in plants?

A

Source of energy of converted into polysaccharides (such as starch) and stored.

157
Q

What is a companion cell?

A

Long thin cells, that unlike the sieve tube element, still has a nucleus, mitochondria, ribosomes and rough endoplasmic reticulum. These cells perform the metabolic functions that maintain the sieve tube.

158
Q

What do transfer cells do?

A

They help to actively transport sugars, amino acids and other organic solutes produced as a result of photosynthesis into the sieve tube.

159
Q

How are the transfer cells adapted to their function?

A
  • Their cell walls and cell surface membranes have many small infoldings that increase their surface area.
  • They contain numerous plasmodesmata linking their cytoplasm with that of adjacent cells.
  • They have lots of mitochondria to provide the energy necessary to load the solutes into the sieve tube.
160
Q

How are sugars and other solutes moved along the phloem?

A

1) Loading of solutes to the phloem increases solute concentration, which draws water into the sieve tube by osmosis from adjacent xylem vessels.
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 difference in pressure between the loading and unloading sites causes mass flow along the sieve tube: fluid carrying dissolved substances moves along the phloem sieve tube from high to low pressure.

161
Q

As well as transporting water why are xylem vessels also important?

A

Xylem vessels are important in supporting plants.

162
Q

Lignin not only waterproofs but …

A

Make xylem vessels much stiffer and gives the plant greater tensile strength.

163
Q

How is lignin laid down?

A

It is often laid down in spirals or rings.

164
Q

Are phloem sieve tubes lignified?

A

No

165
Q

Are sclerenchyma fibres lignified?

A

Yes they are lignified and die once lignified leaving hollow fibres.

166
Q

What is a turgid cell?

A

A plant cell is described as being turgid when the cell contents press against the cell wall. If a plant cell is surrounded by a solution with a high concentration of water molecules, water will move into the cell by osmosis. As a result, the volume of the cell contents will increase and press against the cell wall.

167
Q

Plant fibres are used to make clothing, rope, floor coverings, paper and more. Plant fibre can be used in this way because?

A

They are:

  • long and thin
  • flexible
  • strong
168
Q

How doe we extract fibres from plants?

A

To obtain fibres we must take the plant apart. This can be done mechanically by pulling out the fibres or by digesting the surrounding tissue. Fortunately for us, cellulose and particularly cellulose combined with lignin is very resistant to chemical and enzyme degradation, whilst the polysaccharides that hold the fibres together can be dissolved away.

169
Q

The more … present the harder it is to separate the fibres.

A

Lignin

170
Q

What is the traditional process whereby stems are left in heaps allowing bacteria to break down the tissue, leaving the fibres?

A

Retting

171
Q

How do some plants defend themselves against attack?

A

Many plants have adaptations that provide chemical defences to repel or even kill animals that feed on them. One strategy is to produce a chemical that is distasteful or even toxic. If the animal takes a bite and the taste is offensive (usually bitter) the animal is deterred from further feeding. If its chemicals kill the predator, the plant will avoid future attacks.

172
Q

What is the process bacteria use to reproduce?

A

Binary fission

173
Q

Describe what happens in binary fission.

A

The circular DNA replicates and a new cell content is synthesised before new cell wall forms to divide the cell into two roughly equal halves.

174
Q

With bacteria reproducing so quickly why are we not completely overrun?

A

The reason is that these of growth only occur under ideal conditions, when there is sufficient nutrients, optimum temperature, optimum pH, no build up of waste products and sufficient oxygen if the bacteria relies on aerobic respiration. In reality, conditions are rarely ideal.

175
Q

What are the four phases of bacteria reproducing?

A
  • Lag phase
  • Log/exponential growth phase
  • Stationary phase
  • Death/logarithmic decline phase
176
Q

What is the lag phase?

A

This is when the cells are adjusting to the conditions (e.g. enzyme synthesis)

177
Q

What is the exponential phase (log phase)?

A

Cells are dividing exponentially at fastest rate possible for conditions.

178
Q

What is the stationary phase?

A

Growth is limited by lack of food, build of toxins, changing pH (same amount of replicating as dying)

179
Q

What is the death phase?

A

Number of cell deaths is greater than cells formed.

180
Q

What are the five stages of drug testing?

A
  • Pre-clinical testing
  • Clinical trials phase 1
  • Clinical trials phase 2
  • Clinical trials phase 3
  • After licensing
181
Q

Describe what happens during pre-clinical testing.

A

Animal studies and laboratory studies on isolated cells and tissue cultures assess safety and determine whether or not the compound is effective against the target disease.

182
Q

Describe what happens during clinical trails phase 1.

A

A small group of volunteers are told about the drug and given different doses. These volunteers are normally healthy, but there are circumstances when drugs are first tested on sick patients. The trial confirms whether or not the compound is being absorbed, distributed, metabolised and excreted by the body in the way predicted by the laboratory tests. The effects of different doses are monitored.

183
Q

Describe what happens during clinical trails phase 2.

A

Small group of volunteer patients (100-300 with the disease) are treated to look at the drug’s effectiveness. If results are promising, phase 3 trials are set up.

184
Q

Describe what happens during clinical trails phase 3.

A

A large group of patients (1000-3000 people) is selected and divided randomly into two groups. One group is given the compound being investigated. The second is given an inactive ‘dummy’ compound known as a placebo. If there is an existing treatment for the disease, the standard treatment is given instead of the placebo. It is important that neither the Doctor or the patient know who is having the placebo or standard treatment. This is known as a double-blind randomised controlled trial. If the compound being investigated is effective, then the results will show a statistically significant improvement in the patients receiving the treatment compared with patients given the placebo or standard treatment. The tests also look for any adverse reactions in the patients.

185
Q

Describe what happens during after licensing.

A

Trials continue to collect data on the effectiveness and safety of a new drug after the drug has been licensed.

186
Q

Seeds are adapted to ensure they:

A
  • Protect the embryo
  • Aid dispersal
  • Provide nutrition for the new plant
187
Q

In flowering plants how is the ovule fertilised?

A

It is fertilised by the nucleus from a pollen grain and develops into a seed.

188
Q

What happen to the ovule once it has been fertilised?

A

The outer layers of the ovule become lignified forming a tough seed coat that protects the embryo within the seed. The surrounding ovary develops into the fruit, which often has an important role in seed dispersal.

189
Q

In some species where does the stored food remain (seeds)?

A

Outside the embryo in a storage tissue called the endosperm.

190
Q

Seeds that have an endosperm are referred to as

A

Endospermic

191
Q

Why is it important that seeds are widely dispersed?

A

This helps the offspring to avoid competing with their parent plant or with each other and it also lets the plants colonise new habitats.

192
Q

Hat are the ways seeds are dispersed?

A
  • Wind
  • Animal
  • Water
  • Self-dispersal
193
Q

Where does the seed take in the water?

A

The seed takes in water through a pore in the seed coat.

194
Q

What happens once water has been absorbed into the seed?

A

Absorbing water triggers metabolic changes in the seed.

195
Q

What is the seed coat known as?

A

Testa

196
Q

What are cotyledons?

A

A leaf from an embryo plant inside a seed. In some plants, when seeds germinate, the cotyledons may stay below the surface of the soil and supply the developing plant with nutrients. In others, the cotyledons emerge from the soil, turn green and photosynthesise. The number of cotyledons present is one of the features used in classifying plants. Monocotyledons have one cotyledon and dicotyledons have two.

197
Q

What is a plumule?

A

A young plant shoot. If the seed of a dicotyledon plant such as a bean is cut open, an embryo can be seen. A bean embryo has two cotyledons which act as a food store, a radicle or young root, and a plumule or young shoot.

198
Q

What is a radicle?

A

A young plant root. If the seed of a plant such as a bean is cut open, an embryo can be seen. This embryo has two cotyledons which act as a food store, a plumule or young shoot, and a radicle or young root.

199
Q

What is the difference between a plumule and a radicle?

A

Plumule after germination grows into a shoot, that is it grows upwards out of the soil. Whereas, a radicle after germination grows into a root, that is, it begins to grow down into the soil.

200
Q

Describe the metabolic changes that occur in a seed after water has been absorbed.

A

Enzymes are produced that mobilise the stored food reserves. Maltase and amylase break the starch down into glucose, which is converted into to sucrose for transport to the radicle and plumule. Proteases break down the proteins in the food store into amino acids; lipase break down stored lipids into glycerol and fatty acids.

201
Q

Why is starch easy to extract from plants?

A

It is because starch is in granules, which do not dissolve in water, but can be washed out.

202
Q

What is gelatinisation?

A

When starch granules are heated in water they suddenly swell, absorb water and thicken the liquid.

203
Q

What is the benefit of starch based packaging?

A

It means this form of packaging can be used instead of polystyrene or polyethylene.

204
Q

What can we use vegetable oils for?

A

Biofuels

205
Q

What is the benefit of biofuels?

A

They produce less sulphur dioxide than diesel and less carbon dioxide.

206
Q

Name three reasons why the use of oil-based plastics and fuel is not sustainable.

A
  • Burning fossil fuels contributes to a net increase in atmospheric carbon dioxide concentration, which is likely to contribute to climate change.
  • Oil reserves will eventually run out
  • Plastics generate non-biodegradable waste, creating major waste disposal problems.
207
Q

What can help reduce the problem of sustainability regarding the use of oil-based plastics and fuels?

A

The use of plant-based products

208
Q

Why is it more sustainable to use plant-based products instead of oil-based products?

A
  • Burning fuel made from vegetable oil also produces carbon dioxide, this carbon dioxide has been removed from the atmosphere relatively recently when the crop that produced the oil was grown. The carbon dioxide released will be about the same quantity as the amount fixed, so there is no net change in carbon dioxide in the atmosphere (carbon neutral). This is not the case when burning fossil fuels, which release carbon dioxide stores built up over long periods of time.
  • Renewable - more plants can be grown
  • Ethanol is clean burning (no sulphur)
209
Q

At are the problems with trying to grow biofuels?

A
  • We already cultivate a large proportion of the planet’s surface for food, so there is not much room left for growing biofuels and other plant material. Plants for biofuels are replacing rainforests and also food crops.
  • Many of the remaining uncultivated areas are unsuitable for agriculture and/or are essential for wildlife conservation or water conservation. The human population is increasing rapidly(Land availability)
  • Intensive agriculture is itself very energy demanding
  • Some of the plant alternatives do not have the same desirable qualities as the oil-based products.
  • Some plant alternatives may require the consumption of as much or more energy in production and transport of the product, compared with the oil-based products.
  • Ethics of using food as fuel
210
Q

What is your ecological footprint?

A

Is the area of land you would require to support your current lifestyle.

211
Q

What is the primary threat to most species and habitats?

A

Human activity

212
Q

What are the threats by humans to species and their habitats?

A
  • Land development (causes habitat destruction, fragmentation and depredation)
  • Over exploitation
  • Introduction of alien species
  • Pollution
213
Q

What are the two types of conservation?

A
  • in situ

- ex situ

214
Q

What is an in situ conservation?

A

In place, i.e. In its natural habitat.

215
Q

What is ex situ conservation?

A

Outside of place, i.e. In a zoo or wildlife park

216
Q

Why is in situ better than ex situ conservation?

A
  • Conserves habitat diversity
  • Conserves more species including, small, boring and ugly ones.
  • More genetic diversity (larger population)
  • Avoids ethical issues with keeping animals in captivity
217
Q

Why is in situ not always possible?

A
  • Specific threats such as poaching

- Dramatic habitat loss, due to humans (directly or climate change)

218
Q

What are the benefits of ex situ?

A
  • No poaching, therefore the animals are safe
  • Education of the public
  • Raises money for in situ conservation
  • Allows research
  • Breeding programmes increase numbers
  • Reintroduction
219
Q

What are the problems of ex situ?

A
  • Habituation of animals to humans
  • Concerns over animal welfare
  • Inbreeding, reduction in genetic diversity
  • Animals can be kept in poor conditions
  • Animals behave unnaturally
  • 95% of species in zoos are not endangered
220
Q

How can we reduce the problem of habituation of animals to humans?

A
  • Less human contact
  • Large enclosures
  • Allow the animals to hunt
221
Q

How can we reduce the problems regarding concerns over animal welfare?

A
  • Make sure the animals have enough space
  • Mimic their natural habitat
  • Enrichment activities
222
Q

How to reduce the problems of inbreeding and the reduction in genetic diversity within zoos and wildlife parks?

A
  • Managed breeding by keeping stud books
  • Capture new individuals
  • Exchange of individuals within zoos
  • Do not allow organisms to repeatedly breed with the same partner
  • Select partner, possibly by adding a potential partner to a cage, IVF or inter-zoo swapping
223
Q

Why is the plant alternative form of packaging better?

A
  • Renewable

- Biodegradable

224
Q

What are the problems with packaging made from plants?

A
  • Land availability to grow plants
  • Using food sources for packaging
  • In landfill even biodegradable products do not biodegrade due to anaerobic condition.
225
Q

Why are building materials unsustainable?

A
  • Rocks are non-renewable

- Quarrying degrades the environment -> habitats and water surfaces

226
Q

Why is the plant alternative of building materials better?

A
  • Renewable

- Wood can be sourced sustainably from managed woodlands

227
Q

What are the problems with using plant materials for building?

A
  • Wood is not suitable for all types of structures

- Modern building materials have important properties that wood does not (e.g transparency)

228
Q

What are the main aims of captive breeding programmes?

A
  • Increasing the number of individuals of the species if numbers are very low (reduce the risk of extinction).
  • Maintaining genetic diversity within the captive population
  • Reintroducing animals into the wild if possible
229
Q

How can genetic diversity be lost?

A

Genetic drift

230
Q

What is genetic drift?

A

In a small population, some of the alleles may not get passed on to offspring purely by chance. This changes the allele frequencies over time and leads to a reduction in genetic variation.

231
Q

What environment is best for individuals in a population having similar genotypes?

A

Stable environments as the organisms have adapted to the environment and it is not changing.

232
Q

What type of population is better if the environment is changing?

A

A genetically diverse population

233
Q

What is an inbreeding depression?

A

Inbreeding is breeding closely related individuals together. The offspring are likely to become homozygous for more and more harmful recessive alleles. This may result in the offspring of animals or plants which have been inbred for a number of generations showing inbreeding depression and producing a lower yield or being less fertile.

234
Q

When does inbreeding occur?

A

In a small population, whether in the wild or in captivity.

235
Q

What is the importance of keeping studbooks?

A

The studbook for an individual species shows the history and location of all the captive animals of that species in the places that are co-operating in an overall breeding plan.

236
Q

What is captive breeding for reintroduction?

A

This involves breeding animals in captivity that are then returned to their native habitats.

237
Q

What are plants threatened by?

A
  • Habitat destruction
  • Climate change
  • Over-harvesting
238
Q

Name a seed bank project

A

The Millennium Seed Bank (MSB)

239
Q

What is the aim of the Millennium Seed Bank Project?

A

To conserve seed samples from threatened species of plants

240
Q

What are the seed collections also used for?

A

Research, habitat restoration and species reintroductions.

241
Q

How do you work out the heterozygosity index?

A

Number of heterozygotes / number of individuals in the population

242
Q

How can allele frequency change?

A

Allele frequency changes because of a change in selection pressure.

243
Q

What is molecular phylogeny?

A

Is the analysis of genetic material to establish evolutionary relationships between organisms.

244
Q

What are the three key aspects of the scientific process to try and ensure reliability and validity?

A
  • Peer review
  • Dedicated scientific journals
  • Scientific conferences
245
Q

Before research gets published in a journal it is sent off to two or three other scientists in the same area of work. What do they look at?

A
  • Is the paper valid? (Are the conclusions based on good methods and are the data reliable)
  • Is the paper significant? (The paper must make a useful addition to the existing body of scientific knowledge)
  • Is the paper original?
246
Q

What is the tonoplast membrane?

A

A membrane around the vacuole to control movements in and out of it.

247
Q

What are the amyloplasts?

A

Cells that store starch granules.

248
Q

What is between plant cells? What does it contain?

A

The middle lamella is between cell walls of adjacent cells and contains pectin, which holds cells together.

249
Q

Give an example of cells that have a secondary cell wall? Why?

A

Xylem vessels and sclerenchyma because it makes them stronger and more flexible.

250
Q

Compare and contrast the structure of starch and cellulose (4marks)

A

Both are polysaccharides made of monosaccharide monomers, but in cellulose the monomer is Beta-glucose whereas in starch it is alpha-glucose. All hydrogen bonding in starch is on one side of the molecule, making it a spiral, but in cellulose they are on both, making it long parallel chains.

251
Q

Describe the structure of the phloem

A

Living cell with reduced cytoplasm and perforated and walls called sieve plates. Phloem have many pores on their sides, some of which communicate via cytoplasm-filled pores called plasmodesmata, with an adjacent living cell called the companion cell, giving phloem cells metabolic energy for the transport of sugar solution.

252
Q

Describe the structure of sclerenchyma cells.

A

Dead cells with a very thick cell wall which is heavily lignified. Not in rings or spirals. Lumen is very small and may be absent.

253
Q

What are the similarities between historical and contemporary drug trials?

A
  • Both isolate a possible drug/ treatment

- Both initially tested on a small number of patients and then a larger group of patients.

254
Q

What are the differences between historical and contemporary drug trials?

A
  • Modern protocols test on animals before phase 1
  • Modern protocols have phase 1 testing where the drug is tested on healthy people
  • Modern protocols have double blind trials, including using a placebo, undertaken to collect data for statistical analysis
255
Q

List aseptic techniques.

A
  • All equipment, including agar, Petri dishes, pipettes and culture tube necks should be sterile.
  • Flaming this equipment in a Bunsen flame ensures sterility
  • Inoculation (adding an organism) should be done with a flamed instrument
  • Lids should be replaced as quickly as possible
  • Lids should be taped across with sticky tape
256
Q

What are the three main roles in conservation?

A
  • Education
  • Scientific research
  • Captive breeding programmes
257
Q

What is the education to people from zoos about?

A
  • Illegal trade in animals and products
  • The need for biodiversity
  • Captive breeding programmes
258
Q

What is the scientific research done in zoos?

A
  • Control of disease
  • Behaviour, to understand needs
  • Techniques, to improve breeding
259
Q

Why are seeds stored rather than plants?

A
  • Less space is required so more species can be held in the available space
  • Most plants produce large numbers of seeds so collecting small numbers is unlikely to damage the wild population.
  • Easier to store because dormant
260
Q

Describe how the seeds are collected and then stored.

A

1) Seeds are collected from a number of individual plants (seeds from several plants are likely to have a higher diversity)
2) Seeds x-rayed to check for fully formed embryos (only viable seeds are selected for storage)
3) Seeds dried to remove water (reducing water content increases the length of time a seed can be stored and remain viable)
4) Seeds stored in the cold -20 degrees celsius (reducing the temperature also increases the length of time a seed can be stored and remain viable.
5) Some seeds periodically germinated to check viability (some seeds are planted to check that they will germinate and grow)
6) If less than 75% germinate, those that did germinate are allowed to grow into mature plants that produce their own seeds which are stored. If 75% or more germinate, the remaining seeds are retained in cold storage and can be checked again for viability.

261
Q

what are the issues with seed banks?

A
  • Stored specimens have to be replanted as they lose viability
  • Only some biodiversity can be stored
  • Certain seeds cannot be stored this way
  • Seed banks are expensive to build and to run; power has to be sustained to keep the seeds very cold.

Biology AS Level (4 decks)

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