Topic 4 SNAB Biology

Some questions with bullet pointed answers on some of the key topics within topic 4 of the SNAB BIOLOGY A-LEVEL course

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  • Created by: VicC
  • Created on: 28-05-10 21:38

Define SPECIES, HABITAT and POPULATION.

SPECIES

  • a group of organisms with similar morphology (looks the similar), physiology (internally similar) and behaviour
  • which can interbreed to produce fertile offspring
  • and which are reproductively isolated from other species

HABITAT

  • a place with a distinct set of conditions where an organism lives

POPULATION

  • a group of individuals
  • of the same species
  • found in an area
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Define COMMUNITY, NICHE and GENE POOL.

COMMUNITY

  • the various populations
  • of different species
  • that share an ecosystem/ habitat

NICHE

  • the precise role of an organism in its environment;
  • the sum total of all the organisms' interactions

GENE POOL

  • the sum total of all alleles of all genes within a population
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Define ADAPTATIONS and descirbe the different TYPE

  • features which enable an organism to survive and reproduce
  • being specialised to suit an environment in which the organism lives

BEHAVIOURAL ADAPTATIONS: any actions by organisms, which help them to survive and reproduce.

PHYSIOLOGICAL ADAPTATIONS: features of the internal workings of an organism, which help them to survive and reproduce.

ANATOMICAL ADAPTATIONS: physical structural features of an organism's body, which help them to survive and reproduce

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What is CO-ADAPTATION?

  • two organisms become dependent of each other
  • and more and more closely adapted
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What is NATURAL SELECTION and what is EVOLUTION?

NATURAL SELECTION

  • organisms change over time as they adapt to their changing environment

EVOLUTION

  • a change in the frequency of alleles over time
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What were the KEY OBSERVATIONS and CONCLUSIONS for

1. OBSERVATION: more offspring produced than can survive

  • STRUGGLE FOR EXISTENCE:
    • competition for survival between members of the same species for resources such as food
    • limited resources between too many organisms
    • population size is limited by environment

2. OBSERVATION: huge amount of inherited variation between species

  • SURVIVAL OF THE FITTEST
    • organisms best adapted to the environment are more likely to obtain resources (e.g. food)
    • and so more likely to survive and reproduce
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Describe how EVOLUTION occurs.

  • Variation exists within a species through RANDOM GENETIC MUTATIONS, which form new alleles
    • Meiosis mixes up existing allele combinations
  • Change in environment causes a change in the selection pressure
  • Which causes a change in allele success
    • Some alleles are favourable and some are harmful
    • Organisms with favourable alleles survive and reproduce, forming fertile offspring
    • Those who have the harmful allele do not
  • Inhertitance of the favourable allele occurs, increasing the frequency of that allele in the next generation
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Explain the HIERARCHY in TAXONOMY (in order from l

Kingdom

Phylum (plu. Phyla)

Class

Order

Family

Genus (plu Genera)

Species

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Name and breifly describe the 3 domains of the DOM

  • ARCHAEA
    • organisms from PROKARYOTE kingdom
    • no nucleus
    • e.g. methanogens
  • BACTERIA
    • organisms from PROKARYOTE kingdom
    • no nucleus
    • e.g. all other bacteria (apart from methanogens)
  • EUCARYA/ EUKARYOTA
    • organisms from the other four kingdoms (not prokaryote)
    • eukaryotic
      • plants/ animals/ fungi
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Explain BIODIVERSITY by defining SPECIES, GENETIC

SPECIES DIVERSITY:

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

GENETIC DIVERSITY:

the variety of alleles within a species

ECOLOGICAL DIVERSITY:

the variety between different habitats

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What is 'ENDEMISM'?

  • when a species is unique to a single place
  • and isn't naturally found anywhere-else in the world
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How do you measure GENETIC DIVERSITY within a spec

  • FIND THE NUMBER OF DIFFERENT ALLELES IN A GENE POOL.

by:

  • DNA SEQUENCING:
    • to determine the bases in a DNA segment
    • determining the alleles present
  • GEL ELECTROPHORESIS:
    • DNA --> fragments
    • identify different alleles
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How do you measure SPECIES diversity?

1. SPECIES RICHNESS:

  • count the number of different types of species in a given habitat
  • more types of species: HIGH SPECIES RICHNESS

2. SPECIES EVENESS:

  • count the number ofa different types of species in a given habitat
  • AND the number of individuals of each species
  • similar abundances: HIGH SPECIES EVENESS

HIGH SPECIES RICHNESS AND HIGH SPECIES EVENESS = highly diverse

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Describe and explain the function of these organel

  • AMYLOPLAST:
    • has a double membrane
    • storage of starch grains
  • PITS:
    • regions of thin cell wall
    • allows transport of substances between cells
  • PLASMODESMATA:
    • channels in cell wall that link adjacent cells together
    • allows transport and communication between cells
  • MIDDLE LAMELLA:
    • is an adhesive sticking adjacent plant cells together
    • gives plant stability
    • contains pectins
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Describe a VACUOLE and what is its function?

  • VACUOLE:
  • contains cell sap
  • keeps cell turgid (stops plant wilting)
  • involved in the breakdown and isolation of unwanted chemicals in cell
  • has a tonoplast- controls what enters and leaves the vacuole
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Describe the comparisons between STARCH and CELLUL

  • S: alpha-glucose monomer
  • C: beta-glucose monomer
  • S: branched amylopectin (1, 4 and 1,6 glycosidic bonds) and unbranched amylose (1, 4 glycosidic bonds)
  • G: unbrached
  • S: chains with side branches; amylose is a helical coiled structure
  • G: long straight chains
  • S: compact energy storage molecule in plants
  • C: strong structural support for cells
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How does CELLULOSE give plant cells STRONG STRUCTU

  • large number of hydrogen bonds forming bundles called MICROFIBRILS
  • microfibrils:
    • arranged at many different angles
    • in layers
    • within matrix of hemicelluloses and pectins

Hemicelluloses and pectins = glue that holds microfibrils together

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How is water transported up xylem vessels? (Descri

TRANSPIRATION: water evaporated from the surface of spongy mesophyll cells and diffuses down the diffusion gradient through stomata of leaves

Water in the spongy mesophyll leaves is replaced from the xylem, lowering hydrostatic pressure at the top of the vessel, resulting in water being drawn up from below: TRANSPIRATION STREAM.

Hydrogen bonding between water molecules allows cohesion between water molecules; this keeps water as a continuous column in the xylem vessel: COHESION-TENSION THEORY.

Forces of ADHESION occur between water molecules and the xylem cell walls.

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Compare XYLEM VESSELS and SCLERENCHYMA FIBRES.

  • X: transport water and minerals up the plant AND provide support
  • S: provide support
  • X: cell walls are thickened with lignin, making them strong and waterproof
  • S: cell walls are thickened with lignin, making them strong and waterproof BUT contain more cellulose (microfibrils)
  • X and S: made of bundles of dead cells
  • X and S: hollow lumen
  • X and S: arranged in columns
  • X: long cylinders with no end walls
  • S: short structures with taperend ends (ends closed)
  • X: has pits in walls-allows transport of water & mineral ions in and out of xylem
  • S: no pits in walls
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Describe how to investigate the lack of calcium io

1. Take 30 seedlings of the same plant (same age and height)

2. Split seeds into 3 groups of 10

3. Plant each group into separate pots

4. Make up 3 nutrient broths with varying concentration of calcium ions:

  • 1 broth: high concentration
  • 1 broth: medium concentration
  • 1 broth: low concentration

5. Give each group one of the three broths

6. Record the height of the plants after 7 weeks

7. Calculate the average height of each group of plants

Controls: amount of water and sunlight

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How do you extract fibres from plants?

1. Mechanically pull out fibres

2. Digest the surrounding tissues

3. RETTING:

  • pile stems in heaps
  • allows bacteria and fungi to rot plant
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Describe why plant fibres are strong in terms of i

1. The arrangement of cellulose microfibrils in the (primary) cell wall

  • microfibrils are arranged in a net-like criss-cross arrangement
  • at many different angles
  • giving it strength

2. The secondary thickening of cell walls

  • plant cells can produce a secondary cell wall between the normal cell wall and the cell membrane
  • giving more lignin
  • its microfibrils are arranged in sheets, running in one direction only
  • giving it strength
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Describe how to measure the TENSILE STRENGTH of pl

1. Attach the plant fibre to a clamp stand

2. Attach a mass to the other end of the planf fibre, adding more mass in small constant increments until the fibre snaps

3. Record the mass needed to break the fibre

4. Repeat, increase reliability of results.

5. Safety: make sure tha area where the mass stops ins clear/ has a large container containing polysterene

6. Control: Make sure that the plant fibres are the SAME WIDTH and LENGTH.

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Describe how to investigate the ANTIBACTERIAL prop

1. Take extracts from 1 plant by drying and grinding each plant and soak in ethanol; control: plants must be same size so same amount of extracts is used.

3. Evenly spread a sample of bacteria onto an agar plate.

4. Dip discs of absorbant paper into one of the plant extracts; control: discs must be same size so the same amount of liquid is absorbed by each.

5. Have a control disc which is ONLY soaked in ethanol.

6. Place paper dics onto the agar plate (spread out evenly).

7. Replace the lid and seal, but so gases cans still enter and leave.

8. Incubate the the plate at about 25 degrees centigrade-allow bacteria to grow.

9. Measure the clear patch around each disc: INHIBITION ZONE. Larger the inhibition zone, the more effective the plant extract (better antibacterial properties)

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Comments

Kate

Thanks this is really good :)

Noor

Wow awesome, very helpful!

Thank you ~ I have a mock today and only used this for revision :) 

shalom

For those who are new to SNAB, this is unit 2 revision material for AS. 

ermira123

this is really helpful however where is the part about seeds and sustainability?

ermira123

and also zoos

ermira123

and also zoos

Imanrobl

fab

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