AS Topic 4 Flashcards
What is the structure and function of a plant cell wall?
Composed of cellulose
Provides cell with structural support
What is the structure and function of the middle lamella?
Outermost layer of cell, produced between adjacent new cells
Holds cell walls together by acting like a sticky glue
What is the structure and function of the plasmodesmata?
Narrow threads of cytoplasm connecting cytoplasm of neighbouring cells (cytoplasmic connection)
Allows efficient exchange of signalling molecules between neighbouring cells (allows transport/communication)
What is the structure and function of a pit?
Thin region of the cell wall arranged in pairs
Facilitates the transport of substances
What is the structure and function of a chloroplast?
Double membrane with thylakoids containing chlorophyll in stacks called grana
Site of photosynthesis
What is the structure and function of an amyloplast?
Small membrane bound organelles containing starch granules
Store starch and synthesise it
What is the structure and function of the vacuole and tonoplast?
Vacuole - cell sap filled sac, tonoplast is the membrane that surrounds it
Vacuole keeps cell turgid, tonoplast regulates ion movements around cell
What 3 basic principles do plant cells use to build structures?
Strong cell walls from cellulose
Columns and tubes made from specialised cells
Stiffen some of these cells with lignin
What is cellulose?
A polysaccharide made up of beta glucose units
How do 2 beta glucose molecules join?
Via a condensation reaction
B glucose molecules are rotated alternately through 180 degrees, creating a 1-4 glycosidic bond
What is a cellulose microfibril?
A bundle of around 60-70 cellulose molecules
What is the structure of a cellulose microfibril?
Parallel chains of cellulose polymers
H bonds form between the neighbouring molecules due to hydroxyl groups
What holds cellulose microfibrils together?
Hemicellulose and pectins (short polysaccharides) which bind to the cellulose and each other
What is the xylem and how is it adapted for it’s function?
Long tube like structure formed from dead cells placed end to end for the transport of water and mineral ions
Adaptations: hollow lumen, no end walls (allows mass flow), thickened with lignin (strength to withstand hydrostatic pressure), pits allow lateral movement of water (in case of air bubbles)
What happens in mature lignified xylem cells?
They are dead
What is the phloem and how is it adapted to it’s function?
A transport tissue made of sieve tube elements joined together for the transport of sucrose and other dissolved nutrients
Adaptations: sieve cells have no nucleus or other organelles (maximises space for translocation), they have a companion cell which provide the energy for active transport (lots of mitochondria), sieve pores allow continuous movement, plasmodesmata links sieve tubes to companion cells
What is the difference between mature phloem and xylem cells?
Mature phloem contain living cells, unlike mature xylem which are dead
What is the sclerenchyma and how is it adapted to it’s function?
Support fibres made of bundles of dead cells thickened with lignin - provides mechanical support
Adaptations: lignification of cell wall, hollow inside, dead cell
Why would the structure of sclerenchyma make these fibres useful to make rope?
Thick lignin walls for strength
Lignin makes them waterproof
Flexible so do not break easily
Light because they are hollow
Why are plant fibres so strong?
Due to factors affecting the cell wall:
- the arrangement of microfibrils in a mesh like pattern
- secondary thickening (development of a secondary cell wall which contains lignin)
How is water transported in the xylem?
Transpiration stream: water is pulled up as it evaporates out of the stomata due to the tension of the H bonds and cohesive forces
How are inorganic ions transported by the xylem?
The movement of water through the xylem provides a mass flow system for transport
Why are plant fibres useful to humans (and give an example of how they’re used)?
They are very strong
Ropes and fibres
Why are plant fibres sustainable?
Less fossil fuels used
Can be replanted for next generation (resources made available for future generations)
Plant fibres are biodegradable
Cheaper and easier to grow and process
How can starch contribute to sustainability?
Can be used to make bioplastics, which are more sustainable as crops can be regrown and there are no fossil fuels
Can make fuel from starch
How can the use of starch (over plastic) contribute to sustainability?
Starch is a renewable resource, plastic is derived from oil which is a non renewable resource
no fossil fuels
What is the importance of water to plants?
Solvent properties (can transport dissolved substances)
Thermal properties (cools and heats slowly to avoid rapid changes in internal temp)
Density/freezing (ice is less dense than water as water expands as it freezes)
Cohesion and surface tension (H bonds keep water molecules in a column in xylem vessels)
What is the importance of water and different inorganic ions to plants?
Water - photosynthesis, transport medium, turgidity, temp regulation
Mg ions - production of chlorophyll (yellow leaves, plants smaller)
Nitrate ions - plant growth, DNA and protein synthesis (stunted growth)
Ca ions - cell wall growth (middle lamella - leaves cannot grow fully without)
What are the conditions required for bacterial growth?
-nutrients (materials to grow and respire)
-oxygen (if respiring aerobically)
-optimum temp/pH to allow correct enzyme function
What 2 things must new drugs be tested for?
Efficacy
Side effects
Why are healthy volunteers in a drug trial given different doses of the drug or placebo?
Check for side effects, different doses to determine safe dose, placebo to ensure side effects were due to drug
Why are placebos used to test the efficiency of new drug treatments?
Placebo = inactive substance
Used as a control
So that psychological effect does not take place (placebo effect)
What did William Withering do with foxglove?
Used it to treat dropsy - contains drug digitalis. However foxglove can be poisonous so he tried out different doses on his dropsy patients to find a ‘safe’ dose
What are the stage of drug testing today?
Pre-clinical - animal and lab studies
PHASE I - small group of healthy volunteers
PHASE II - small group of volunteer patients who need the drug
PHASE III - large number of patients split into 2 groups (double blind). If successful, becomes licensed
Post licensing - begin development of new drug
What is a double blind trial?
One set of patients receives real drug, other set = placebo
Neither doctors or patients know whether they have received placebo or real drug to remove the bias from results
What is a placebo?
A dummy drug to ensure there is not just a ‘placebo’ effect
How is contemporary drug testing protocol an improvement on the trial used by William Withering?
SAFER - pure drug rather than extract, pre testing on cells/animals rather than people, legislated by regulations
MORE VALID - placebo, double blind, controlling factors in cohort
MORE RELIABLE - more people tested, analysed statistically
what do antimicrobial properties do
kill or inhibit growth of organisms - useful components of drugs
what are aseptic techniques used for
prevent bacterial cultures on agar plates from being contaminated by other micro organisms or human pathogens
steps of aseptic techniques
- all work should be carried out in front of a bunsen burner
- hot agar jelly is poured into a sterilised petri dish and agar is left to cool and set
- an inoculating loop is passed through a hot flame before it is used to transfer bacteria to the culture medium
- petri dishes should only be opened as little as possible at the side facing the bunsen burner
- the lid of the petri dish should be secured with tape at intervals around the dish and stored upside down
- the cultures should not be incubated above 25 degrees celsuus in a school lab
What is a ‘niche’
The role of a species within its habitat - no two species have the same niche as every species has its own specific niche
What does the niche a species have depend on
its interactions with living organisms (biotic) and the nonliving environment (abiotic)
What happens if two species try occupy the same niche
They will compete with one another for the same limited resources
What are the two different types of niche
Structural and feeding
What are adaptations
Special features or characteristics that help the organsim survive
What are the 3 different types of adaptations
Behavioural
Physiological
Anatomical
What are some examples of behavioural adaptations?
Possums playing dead if threatened by predator
Plants turning leaves to sun to maximise photosynthesis
What are physiological adaptations
A feature of the internal workings of organisms that help them to survive of reproduce
What are behavioural adaptations
these are actions by the organism which help them survive or reproduce
What is a species?
A group of organisms with similar morphology, physiology and behaviour, which can interbreed to produce fertile offspring and which are reproductively isolated from other species
What is a habitat?
The area inhabited by a particular organism/species
What is a population?
A group of interbreeding individuals within an area
What is a community?
All the various populations within a habitat
What is an ecological niche?
The way an organism uses/exploits it’s environment
What are some examples of physiological adaptations?
Brown bears hibernate and lower rate of metabolism to conserve energy
Bacteria produce antibiotics to kill threatening bacteria
What is biodiversity?
The variety of species in an ecosystem/community/habitat
The variety of alleles in a gene pool
What are the 3 levels to assess biodiversity?
- number and range of different ecosystems/habitats
- number of species and their relative abundance
- genetic variation within each species
What is a structural adaptation
Structural features of organisms for survival/reproduction
What are some examples of structural adaptations?
Otters have a streamlined shape to glide through water
Whales have a layer of blubber for insulation
What is evolution?
A change in allele frequency over time
How does natural selection occur?
- A population has a naturally occurring genetic variation, with new alleles created through mutation
- A selection pressure occurs in the environment
- Survival of the fittest - advantageous allele
- Organisms with the allele are more likely to survive, reproduce and so produce offspring
- Their offspring are more likely to have the allele, so it becomes more common in the population
Index of diversity
D = N(N-1)/Σn(n-1)
where N = number of organisms in the habitat
n = number of organisms of each species
High D value = greater biodiversity
Takes into account richness and evenness
Count the number of different species and the number of individuals in each species
What does a bigger index of diversity mean
The more biodiverse an ecosystem is
There are many species and fairly evenly distributed so the ecosystem is more stable
Calculating genetic diversity
number of heterozygotes divided by total population
a closer proportion (closer to 1) means higher genetic diversity (same as 100%)
Why is heterozygosity important?
Heterozygosity indicates more individuals carrying different alleles
A low heterozygosity suggests a population. is genetically uniform, which can make it more vulnerable to diseases and environmental changes as a result of inbreeding
What is endemism?
a species only found in one geographical location
What is species richness?
The number of a species present in a given habitat
What is species evenness?
The relative abundances of different species within a community
What does the Heterozygosity Index measure?
Genetic diversity within a species
What can you look at to measure genetic diversity?
Genotype - genetic makeup of an organism
Phenotype - observable characteristics of an organism
What information should you collect for studies of biodiversity?
-presence of endemic/rare species
-use of a diversity index
-genetic diversity of populations
-species richness
Where does genetic diversity come from
Mate selection, random fertilisation, chromosome mutations, meiosis
What is classification, and why do we classify organisms?
The process by which scientists group living organisms
Allows us to look at evolutionary relationships
What is the order of the hierarchy of classification?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What is phylogeny?
The study of the evolutionary history of groups of organisms
What is molecular phylogeny?
Molecular phylogeny looks at molecules (DNA and proteins) to see how closely related
organisms are, e.g. more closely related organisms have more similar molecules.
What are phylogenetic trees?
Representation of evolutionary relationships based on molecular differences accumulated over time
What were the 5 traditional kingdoms?
Plantae
Fungi
Animalia
Protoctista
Prokaryotae
What are the 3 newer domains?
Archaea
Bacteria
Eukaryota
Why were the 3 domains created?
To create 2 separate bacteria categories - molecular phylogeny had determined that archaea and bacteria were more distantly related than initially thought
What is conservation?
The wise use of natural resources and planning and carrying out action to preserve and protect living and non-living resources
What are the 2 approaches to conservation?
In-situ - conserving species in it’s natural environment
Ex-situ - conserving a species by taking it out of it’s natural environment
What happens when a species goes extinct?
There is an overall decrease in biodiversity
What is an endangered species?
One that is threatened with extinction
What is a seed bank?
A facility that conserves plant diversity by drying and storing seeds in a temperature controlled environment
Why do we need seed banks?
25% of Earth’s plant population will disappear over next 50 years.
Save genetic material, plants are essential for animal survival and are a carbon sink
What are the stages of seed bank storage?
Seed collected, transferred to seed bank and unpacked and checked.
Seed cleaned and identification checked
Seeds are dried and packed
Seeds stored at -20 degrees C
Periodic germination trials to check seed viability
What are the advantages of seed banks?
Less labour intensive, more cost effective, makes seeds less vulnerable
Ensures future food security, conserves genetic diversity, protects from natural disasters/mismanagement
What are the disadvantages of seed banks?
Testing seeds is time consuming and expensive, some seeds are difficult to collect
How are seeds selected for storage in the seed bank?
From different plants to provide genetic variation, X rayed to ensure/check viability
What conditions are seeds stored at in seed banks and why?
Cool and dry
- reduce enzyme activity
- prevent germination/keep seed dormant
- reduce growth of microbes
- decrease rate of decomposition
Why is it better to store seeds than fully grown plants?
-seeds are smaller so more can be stored
-seeds can be stored for a longer time (dormancy)
-do not require maintenance in the same way as growing plants
-reduced cost
How can zoos help conservation?
-scientific research
-captive breeding to increase number in the wild
-reintroduction programmes
-education
What are the disadvantages of zoos?
Ethical concerns, captive breeding can lead to genetic drift and loss of genetic diversity, scientific data unreliable due to captivity conditions, certain animals may not breed in captivity
What are the advantages of reintroduction programmes?
Prevents extinction, rebalance ecosystems, restore habitats
What are the disadvantages of reintroduction programmes?
New organisms may carry disease, a struggle to readjust to the wild and therefore may die.
How does the scientific community critically evaluate new theories?
theories communicated to scientific community
peer review
checking of evidence to ensure its validity
Why would you use systematic sampling instead of random sampling?
Due to presence of environmental gradient
How can differences in primary structure of a protein be used to produce phylogenetic trees?
-determine sequence of amino acids
-determine number of similarities/differences in amino acid sequence
-greater number of differences = less related species are
How do zoos play a role in animal conservation?
-research (improving health, developing genetic database)
-education (conservation)
-repopulation (captive breeding and reintroduction programmes)
-protection (from poachers)
How do captive breeding programmes in zoos maintain genetic diversity of captive populations?
-animals carefully selected to prevent breeding between closely related individuals
-stud book used to select individuals for mating (preventing inbreeding)
-exchange of animals between zoos
