4.1 Why so many different species?
Species: A group of organisms with similar morphology, physiology & behaviour which can interbreed to produce fertile offspring, and which are reproductively isolated (in place time or behaviour) from other species.
Habitat: Each has a particular set of conditions which supports a distinctive combination of organisms.
Niche: The way an organism exploits its environment
Comparing ultrastructure of plant & animal cell (p
a-glucose & b-glucose
(Polysaccharides) Starch & cellulose
Starch-1,6 glycosidic bonds
Cellulose-1,4 glycosidic bonds
Cellulose & plant cell wall
Cellulose - polymer of b-glucose (long, unbranched molecule) [straight chain]
Hydrogen bond forms between OH grp of adjacent celluloses, forms bundles-microfibrils
Single H bond=weak BUT lots of H bonds in microfibril makes strong structure.
Plant cell wall formed of microfibrils wound in helical arrangement around cell &
stuck together with polysaccharide glue (hemicelluloses & pectin).
Structure of xylem vessels and sclerenchyma fibres
- Both impregnated with lignin
- Both do not contain living cells (dead)
- Xylem vessel is a hollow tube
- Xylem vessels have perforated end walls
Position in the stem: Xylem & Sclerenchyma
- Both can be found in the stem of a plant
- Xylem vessels found in vascular bundles but sclerenhyma can be found in stem/leaf or any part of the plant that needs strengthening
Function of xylem vessels & sclerenchyma fibres
- Both support plant structure
- Xylem transport water & mineral ion, sclerenchyma fibres do not
How uses of plant fibres & starch contribute to su
Starch= easily extracted from plants. Can be used:
- adhesives, paints, textiles, plaster & toiletries (conditioners)
Thickening: Starch granules heated in H2O,swell,absorb H2O & thicken.-"Gelatinisation"
Super-absorbents: Chemically cross-linked, gelalinised,particles formed- dried, rehydrated
Plant based products could replace oil-based plastics
Plant based plastics developed by fermentation of agricultural waste, so supermarket food packaging e.g. plastic film can be made from starch.
Practical: Tensile strength of plant fibres
Importance of water & organic ions to plants
H2O-Hydrogen bonding makes strong cohesion forces between H2O molecules
Water stays together going through xylem vessels.
Solvent properties:dissolved substances can be transported through xylem & phloem
High thermal stability: helps avoid rapid changes in internal environment.
Nitrate ions: make amino acids, important for plant growth (lack can show yellow)
Calcium ions: role in structure of cell, role in permeability of cell membrane (lack=stunted)
Magnesium ions: needed to make chlorophyll (lack can show yellow)
Practical: Investigating plant mineral deficiencie
Practical: Investigating anti-microbial properties
Comparing historic drug testing with contemporary
William Withering's "digitalis soup": Tested "recipe" on 163 patients and recorded side effects of digitalis eg. nausea, vomiting, diarhhoea. Recovery symptom: lots of urine. Withering realised dosage was vital.
- Applied a standard procedure to discover correct dosage 4 each patient.
- Slowly increased till patients showed signs of vomiting etc
- Then decreased it back; the most effective dose
- Recorded information & after 10 yrs wrote a book
Drug testing today:
Double blind trials-Neither doctor or patient knows the drug or placebo (dummy pill).
III-phased testing: I-Whether drug absorbed metabolised & excreted as predicted
II-Tested for effectiveness
III-double-blind randomised controlled trial- valid testing & adverse effects check
Biodiversity & endemism
Biodiversity: different types of animals and organisms inhabiting/cohabiting the Earth.
Variation of alleles within a gene pool/population.
Endemism:Species only found in a certain area
Species richness:The number of species present in a given habitat.
Species evenness: measures abundance of species in different habitats
BUT does not consider population size of each species.
Biodiversity within a species
Greater variety of genotypes in gene pool, the more genetically diverse the population.
Sources of genetic variation (pg 165)
Adaptations to environment
Behavioural: Any actions by organisms which help them to survive or reproduce.
e.g. plants growing towards the Sun maximising light received for photosynthesis.
Physiological: Features of the internal workings of organisms which help them to survive or reproduce. e.g. A plants physiological adaptation allowing it to tolerate high salt conc.
Anatomical: The structures we can see when we observe or dissect and organism.
e.g. Bodies of bumblebees show adaptatations used to collect nectar and pollen.
Natural Selection and adaptation & evolution
Evolution: A change in ALLELE frequency in a population over a long period of time.
Natural selection--> Survival of the fittest
The mechanism where an organism adapts to changing environments over time.
- Change in environment
- An organism has a random mutation that benefits organism
- More likely to survive & reproduce whilst others die out
- Organism that survives passes on genes
- Offspring reproduce and new adapted species are present
Taxonomy is dynamic, constantly being updated with new discoveries.
Three domains based on molecular phylogeny
Hierarchy or groups:
- Kingdom (Animalia, Plantae, Fungi, Protoctista, Prokaryotae)
King Prawns Count On Funny Gay Species
Methods of conservation of endangered species
Scientific research: Centres 4 research, enable us 2 understand how 2 conserve a species
- Captive breeding programme:
increase no. of individual species -if no.'s low
maintaining genetic diversity [genetic drift=less variation]
& reintroduction to wild if possible
Keeping Studbooks-long & time consuming, have to be maticuluous
Reintroduction to wild programme
BUT-long & complicated process-needs to be taught skill-if habitat still intact.
Millenium Seed Bank!