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Biology Year 1 > Topic 4 > Flashcards

Topic 4 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the cell wall and what is its function?

A

a rigid structure that surrounds plant cells made mainly of cellulose.
it supports plant cells.

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2
Q

what is the middle lamella and what is its function?

A

the outermost layer of the cell.
this layer acts as an adhesive, sticking adjacent plant cells together. it gives the plant stability.

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3
Q

what is the plasmodesmata and what is the function?

A

channels in the cell walls that link adjacent cells together.
allow transport of substances between cells.

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4
Q

what is the pits and what is the function?

A

regions of the cell wall where the wall is very thin.
they are arranged in pairs. the pit in one cell is lined up with the pit in the adjacent cell.
allows transport of substances between cells.

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5
Q

what are chloroplasts and what are the function?

A

small flattened structures surrounded by a double membrane containing thylakoid membranes.
these membranes are stacked up in some parts of the chloroplast to form grana.
grana are linked together by lamellae (thin, flat pieces of thylakoid membrane).

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6
Q

what are amyloplasts and what are the function?

A

a small organelle enclosed by a membrane.
they contain starch granules.
they store starch grains and also convert starch back to glucose for release when the plant requires it.

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7
Q

what are the vacuole and tonoplast and what are the functions?

A

the vacuole is a compartment surrounded by a membrane called the tonoplast.
the vacuole contains cell sap, which is made up of water, enzymes, minerals and waste products.
vacuoles keep the cells turgid, this stops plants wilting.
they are also involved in the breakdown and isolation of unwanted chemicals in the cell.
the tonoplast controls what enters and leaves the vacuole.

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8
Q

what is the function of xylem vessels?

A

to transport water and mineral ions up the plant and provide support.

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9
Q

what is the structure of xylem vessels?

A

-long tube-like structures formed from dead cells, joined end to end.
-the tubes are found together in bundles.
-the cells are longer than they are wide, they have a hollow lumen (no cytoplasm) and have no end walls.
-makes an uninterrupted tube allowing water and mineral ions to pass up through the middle easily.
-the walls are thickened with lignin which helps to support the plant.
-water and mineral ions move into and out of the vessels through pits in the walls where there’s no lignin.

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10
Q

what is the function of sclerenchyma fibres?

A

to provide support.
they are not involved in transport.

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11
Q

what is the structure of sclerenchyma fibres?

A

made of bundles of dead cells that run vertically up the stem.
the cells are longer than they are wide and have a hollow lumen.
they have end walls.
their cell walls are thickened with lignin but do not contain pits.
they have more cellulose than other plant cells.

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12
Q

what is the function of phloem tissue?

A

to transport organic solutes (mainly sugars like sucrose) from the source to the sink.
this is known as translocation.

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13
Q

what is the structure of phloem tissue?

A

phloem is formed from cells arranged in tubes.
phloem tissue contains different types of cells including sieve tube elements and companion cells.
sieve tube elements are living cells and are joined end to end to form sieve tubes.
the ‘sieve’ parts are the end walls, which have lots of holes in them to allow solutes to pass through.
sieve tube elements have no nucleus, very thin layer of cytoplasm and few organelles.
the cytoplasm of adjacent cells is connected through the holes in the sieve plates.
the lack of a nucleus and other organelles in sieve tube elements means they can’t survive on their own so there is a companion cell for every sieve tube element.
companion cells carry out living functions for both themselves and their sieve cells (they provide the energy for the active transport of solutes).

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14
Q

where are the xylem vessels and phloem tissues found in the stem?

A

xylem vessels and phloem tissues form vascular bundles.
sclerenchyma fibres are usually associated with the vascular bundles.

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15
Q

what is starch?

A

the main energy storage material in plants.
cells get energy from glucose.
plants store excess glucose as starch.
starch is insoluble in water so it doesn’t cause water to enter cells by osmosis- this makes it good for storgage.

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16
Q

what is cellulose?

A

the major component of cell walls in plants.

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17
Q

describe the structure of starch.

A

starch is a mixture of two polysaccharides of alpha-glucose (amylose and amylopectin):
amylose- long unbranched chain of alpha glucose. the angles of the glycosidic bonds give it a coiled structure. this makes it compact so good for storage because more can fit in a small space.
amylopectin- long branched chain of alpha glucose. it’s side branches allow the enzymes to break down the molecule to get at the glycosidic bonds easily. this means that glucose is released quickly.

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18
Q

describe the structure of cellulose.

A

cellulose is made of long unbranched chains of beta glucose joined by 1-4 glycosidic bonds.
the glycosidic bonds are straight, so the cellulose chains are straight.
between 50 and 80 cellulose chains are cross linked by a large number of hydrogen bonds to form MICROFIBIRLS.
hydrogen bonds form between the -OH groups in neighbouring cellulose chains.
individually the hydrogen bonds are weak compared with glycosidic bonds, but together the large number of hydrogen bonds in the microfibril produces a strong structure.
the microfibrils are laid down at different angles, which makes the wall strong and flexible, providing structural support for cells.

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19
Q

how are plant fibres strong?

A

the arrangement of cellulose microfibrils in a net-like arrangement.
the secondary thickening of the cell walls (the secondary cell wall is thicker than the normal cell wall and have more lignin).

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20
Q

what is meant by the term tissue?

A

a group of cells working together for a specific function.

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21
Q

what is biodiveristy?

A

the variety of living organisms in an area and it includes species diversity and genetic diversity?

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22
Q

what is species diveristy?

A

the number of different species and the abundance if each species in an area.

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23
Q

what is genetic diveristy?

A

the variation of alleles within a species.
e.g human blood type is determined by a gene with three different alleles.

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24
Q

what is a population?

A

a group of organisms of the same species living in a particular area.

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25
Q

what is endemism?

A

when a species is unique to a single place.

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26
Q

why has biodiversity increased overtime?

A

natural selection leading to adaptation and evolution.

27
Q

why is biodiversity falling?

A

human activities, such as farming and deforestation, are reducing species diversity causing biodiversity to fall.

28
Q

how can biodiversity be maintained?

A

through conservation.

29
Q

what is a habitat?

A

the place where an organism lives.

30
Q

how can biodiversity be measured within a habitat?

A
  • choose an area to sample (randomly to avoid bias)
  • count the number of individuals of each species in the sample area
  • take as many samples as possible
  • use the results to estimate the species richness in the habitat being studied
31
Q

how can biodiversity be measured within a species?

A

measuring genetic diversity using the heterozygosity index.
heterozygotes have two different alleles at a particular locus.
a higher proportion of heterozygotes in a population means that the population has greater genetic diversity.

32
Q

how do you calculate the heterozygosity index (H)?

A

number of heterozygotes/ number of individuals in the population

33
Q

how can biodiversity be compared in different habitats?

A

by calculating the index of diversity.

34
Q

how do you calculate an index of diversity?

A

D = N(N-1)/ sum of n(n-1)
N= total number of organisms of all species
n= total number of organisms of one species

35
Q

what is a niche?

A

the role of a species within its habitat inlcuding its interaction with other living organisms and the non-living environment.
a niche can only be occupied by one species.
if two species try to occupy the same niche there will be competition.

36
Q

what three ways can organisms be adapted to their niche?

A

behavioural adaptations
physiological adaptions
anatomical adaptations

37
Q

what are behavioural adaptations?

A

ways an organism reacts that increases its chance of survival.

38
Q

what are physiological adaptations?

A

processes inside an organism’s body that increase its chance of survival and reproduction.

39
Q

what are anatomical adaptations?

A

structural features of an organisms body that increase its chance of survial.

40
Q

describe the process of natural selection.

A

1) mutations introduce new alleles into a population showing variation within phenotypes.
2) selection pressures create a struggle for survival.
3) individuals with advantageous alleles are more likely to survive, reproduce and pass on the beneficial characteristics to their offspring.
4) overtime the number of individuals with the advantageous allele increases.
5) over generations this leads to evolution.

41
Q

what is a species?

A

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

42
Q

describe the process of speciation.

A
  • GEOGRAPHICAL ISOLATION occurs when a physical barrier divides a population of a species
  • conditions on either side of the barrier will be slightly different resulting in different SELECTION PRESSURES
  • as different characteristics will be advantageous on each side, the allele frequency will change in each population
  • mutations will take place independently in each population, also changing the ALLELE FREQUENCIES
  • the changes in allele frequencies will lead to changes in PHENOTYPE FREQUENCIES (the advantageous phenotype will become more common on that side)
  • eventually the different populations become GENETICALLY DISTINCT
  • individuals from the different populations will not be able to breed with each other to produce fertile offspring (the populations have become REPRODUCTIVELY ISOLATED)
43
Q

how does speciation occur?

A

when populations of the same species become reproductively isolated.
this can be due to:
seasonal changes, mechanical changes, behavioural changes and geographical isolation (physically isolated, different selection pressures, changes in allele frequencies)

44
Q

what is evolution?

A

a change in allele frequency.

45
Q

how can the allele frequency of a population be calculated and what is this used for?

A

the Hardy-Weinberg equation
used to see of the population is changing overtime

46
Q

what does the Hardy-Weinberg principal predict?

A

that the frequencies of alleles in a population won’t change from one generation to the next.
this is only true under certain conditions - it has to be a large population where there is no immigration, emigration, mutations or natural selection.
there also needs to be random mating.

47
Q

how can the Hardy-Weinberg equation be used to predict allele frequency?

A

when a gene has two alleles, the frequency of one of the alleles of the gene can be calculated of the frequency of the other allele is known.
p + q = 1
p= the frequency of the dominant allele
q= the frequency of the recessive allele

48
Q

how can the Hardy-Weinberg equation be used to predict genotype and phenotype frequency?

A

can work out the frequency of one genotype is teh frequency of the others is known.
p2 + 2pq + q2 = 1
p2= frequency of homozygous dominant
2pq= frequency of heterozygous
q2= frequency of homozygous recessive

49
Q

what is the relationship between allele frequency in a population and evolution?

A

evolution is a change in allele frequency
allele frequencies show if a population is changing over time

50
Q

4.5 ii
how are new species formed?

A

reproductive isolation can lead to accumulation of different genetic information in populations, potentially leading to the formation of new species.

51
Q

what is classification?

A

a means of organising the variety of life based on relationships between organisms using differences and similarities in phenotypes and genotypes, and is built around the species concept.

52
Q

what is taxonomy?

A

the science of classification

53
Q

describe early classification systems.

A

only used observable phenotypes to place organisms into groups however scientists don’t always agree on the relative importance of different features and groups based solely on physical features may not show how related organisms are.

54
Q

describe the advantages of new technologies in classification.

A

have enabled organisms’ genotypes (DNA sequence) to be determined which has resulted in new discoveries being made and the relationship between organisms being clarified.

55
Q

why does new data need to be evaluated?

A

to check that experiments or studies were designed properly and that the conclusions are fair.
new scientific data can lead to new taxonomic groupings.

56
Q

how is new data evaluated?

A

scientists share their new discoveries in meetings and scientific journals containing scientific reports.
reports in scientific journals undergo peer review before they are published.
other scientists test the theory by either repeating the exact same experiments or using the theory to make new predictions and then testing them with new experiments.
shows the TENTATIVE NATURE OF SCIENTIFIC KNOWLEDGE (always changing and evolving).

57
Q

how was the three domain classification system developed?

A

based on new data from molecular phylogeny (looks at DNA and proteins to see how closely related organisms are).

58
Q

describe the three domain classification system.

A

in the new three domain system all organisms are placed into one of three domains, large superkingdoms that are above the kingdoms in the taxonomic hierarchy.
the three domains are BACTERIA, ARCHEA and EUKARYOTA.

59
Q

4.10
understand how the arrangement of cellulose microfibrils and secondary
thickening in plant cell walls contributes to the physical properties of xylem
vessels and sclerenchyma fibres in plant fibres that can be exploited by
humans.

A

plant fibres are strong which makes them useful to humans e.g ropes or fabrics like hemp.
they are strong due to the arrangement of cellulose microfibrils in the cell wall and the secondary thickening of cell walls.

the arrangement of cellulose microfibrils in the cell wall:
a net like arrangement (cross linking) makes the wall strong and flexible.
the arrangement of cellulose microfibrils within a matrix of hemicelluloses and pectins gives the plant fibres strength.

the secondary thickening of cell walls:
when sclerenchyma and xylem have finished growing they produce a secondary cell wall between the normal cell wall and the cell membrane.
the secondary cell wall is thicker than the normal cell wall and contains more lignin making plant fibres even stronger.

60
Q

why do plants need water?

A

photosynthesis, to transport minerals, to maintain structural rigidity (water exerts pressure in cell vacuoles) and to regulate temperature (water evaporating from leaves helps cool plants down)

61
Q

why do plants need magnesium ions?

A

for the production of chlorophyll (the pigment needed for photosynthesis)

62
Q

why do plants need nitrate ions?

A

for the production of DNA, proteins (including enzymes) and chlorophyll.
they are also required for plant growth, fruit production, and seed production.

63
Q

why do plants need calcium ions?

A

are important components in cell walls and are required for plant growth.

Biology Year 1 (4 decks)

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