Topic 4 SNAB Biology

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

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

• 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

• two organisms become dependent of each other
• and more and more closely adapted

NATURAL SELECTION

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

EVOLUTION

• a change in the frequency of alleles over time

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

• 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

Kingdom

Phylum (plu. Phyla)

Class

Order

Family

Genus (plu Genera)

Species

• 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

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

• when a species is unique to a single place
• and isn't naturally found anywhere-else in the world

• 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

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

• 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

• 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

• 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

• 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

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.

• 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

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

1. Mechanically pull out fibres

2. Digest the surrounding tissues

3. RETTING:

• pile stems in heaps
• allows bacteria and fungi to rot plant

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

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.

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)