Topic 4 - Biodiversity and Natural Resources Flashcards
Biodiversity
the variety of life, in particular the wealth, of different species that exists as a result of evolution by natural selection
Aspects of biodiversity
habitat/ecosystem diversity - range of habitats and conditions
species diversity - range and abundance of species in a habitat - species richness and relative species abundance
genetic diversity - genetic variation within a species (all the alleles)
Endemism
When a species is found only at a specific geographical location and is not naturally found anywhere else. Endemic species evolve in geographical isolation.
Measuring biodiversity with species richness
- It is measured by random sampling of a habitat and then by counting the number of different species
- The higher the number of species, the greater the species richness
- Does not take relative abundance into account
Measuring biodiversity with species evenness
- a community in which most of the species have similar abundances is said to have high evenness
- does not take into account population size of each species
Measuring biodiversity with genetic diversity
- Genetic diversity within species can be measured by calculating heterozygosity index
- The greater the number of heterozygotes in a population, the greater the genetic diversity is
Heterozygosity index equation
H = number of heterzygotes/number of individuals in the population
Index of diversity formula
D = N(N-1)/∑n(n-1)
N = total number of organisms in all species
n = total number of organisms in one species
Niche
A species’ ecological role, which is defined by the set of conditions, resources, and interactions it needs (or can make use of)
Adaptation
changes in the organism which help them to survive and reproduce according to the environment
Physiological adaptations
features of the internal workings of organisms that help them survive or reproduce e.g. a bumblebee’s biochemical pathway to produce venom
Behavioural adaptations
Any actions by organisms that help them survive or reproduce e.g. bumblebee waggle dance
Anatomical adaptations
structures we can see when we observe or dissect an organism e.g. bumblebee wings, hair, stinger
Evolution
The gradual change in the allele frequencies within a population over time that occurs due to natural selection. This helps species adapt to their habitat
Natural selection
the process whereby organisms better adapted to their environment are morel likely to survive and reproduce so that advantageous alleles increase in frequency over time
Natural selection steps
- population has variation due to genetic diversity in terms of meiosis, mutation, random fertilisation
- the environment presents selection pressures, causing different individuals to have different chances of survival based on their characteristics
- survivors have characteristics for adaptations that increase their chance of survival and reproduction
- offspring inherit advantageous alleles
- over many generations, favourable alleles become increasingly common in the population; allele frequency changes
Natural selection example
- peppered moths have two varieties: light and dark
- darkening of many trees due to pollution helped dark moths camouflage from predators and which helped them adapt and survive in comparison to light moths
- they therefore became more common
Hardy-Weinberg: allele frequency equation
p + q = 1
p = dominant allele
q = recessive allele
Hardy-Weinberg: genotype frequency equation
p^2 + 2pq + q^2 = 1
p^2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q^2 = frequency of homozygous recessive genotype
Hardy-Weinberg Principle
allele frequencies will remain the same from generation to generation assuming that there is no mutation, gene migration, selection, or genetic drift
Allopatric speciation
- occurs when populations of species split into one or more groups and become separated from each other by geographical barriers
mechanism: geographical isolation - no genetic exchange can occur
- if there is sufficient selection pressure or genetic drift, populations will diverge and form separate species
Sympatric speciation
- biological and behavioural changes within a species may lead to reproductive isolation of one population from another
mechanism: ecological separation (populations live in different environments within the same area) and behavioural separation (e.g. feeding, communication, social behaviours)
Classification
a means of organising the variety of life based on relationships between organisms using differences and similarities in phenotypes and in genotypes
Molecular phylogeny
The analysis of molecular differences in different organisms to determine the extent of their evolutionary relationship
The five kingdoms
- animalia
- plantae
- fungi
- protoctista
- prokaryotae
Animalia
- multicellular eukaryotes, all heterotrophs (using food made by others)
- their cells contain a nucleus but no cell walls or chloroplasts
Plantae
- multicellular eukaryotes that are autotrophs through photosynthesis
- their cells contain a nucleus, chloroplasts and cellulose cell walls
Fungi
- usually multicellular eukaryotes, all heterotrophs through saprotrophic or parasitic nutrition
- cells have nuclei and cell walls not made from cellulose
Protoctista
- eukaryotes, both autotrophic and heterotrophic forms exist
- most are unicellular but some are multicellular
- all have a nucleus, some may have cell walls and chloroplasts
Prokaryotae
- prokaryotic organisms, bacteria and blue-green bacteria
- often unicellular
- cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria
Critical evaluation of data by the scientific community
- publishing of work in peer-reviewed and conference journals
- hold scientific conferences
- other scientists critically evaluate the work
- wider scientific community can reproduce and extend the original
- theory becomes accepted and taught and part of wider scientific community
Woese’s discoveries
- defined Archaea as a new domain
- developed the three-domain system based on evidence from chemical analysis (RNA sequencing)
Components of ultrastructure of plant cell
- cell wall
- chloroplast
- amyloplast
- vacuole
- tonoplast
- plasmodesmata
- pits
- middle lamella
Amyloplast
- small, membrane bound organelle containing starch granules
- responsible for storing starch in plants and converting it back to glucose when the plant needs it
Tonoplast
the membrane that surrounds the vacuole of the plant, controlling what can enter and leave
Plasmodesmata
- narrow threads of cytoplasm (surrounded by a cell membrane) that connect the cytoplasm of neighbouring plant cells
- allows substances to be transported between plant cells and facilitates cell to cell communication
Pits
- very thin regions of the cell wall
- pits in adjacent plant cells are lined up in pairs
- facilitates transport of substances between cells
Middle lamella
- the outermost layer of the plant cell and acts like glue to stick adjacent plant cells together
- provides stability to the plant
Starch structure
- composed of polysaccharides amylose and amylopectin
- amylose has unbranched, coiled structure made up of repeated units of α-glucose joined by 1-4 glycosidic bonds
- amylopectin has branched structure made up of repeated units of α-glucose joined by 1-4 glycosidic bonds in a linear chain and 1-6 glycosidic bonds at branch points
- insoluble in water
Cellulose structure
- polymer consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds only
- OH group on carbon 1 is above, so one of the β monomers needs to invert to form a glycosidic bond
- due to the inversion, many hydrogen bonds form between the long chains to form microfibrils
Starch function
- the storage polysaccharide of plants
- mix of amylose and amylopectin means a mixture of rapid and slower glucose and energy release
Cellulose function
- main structural component of cell walls due to its strength, a result of many hydrogen bonds found between the parallel chains of microfibrils
- high tensile strength allows cell walls to withstand turgor pressure
- cellulose fibres and other molecules (e.g. lignin) found in the cell wall form a matrix which increases strength of cell walls
- strengthened cell walls provides support to the plant
Pectin
polysaccharide that acts as glue that holds adjacent plant cells together by cementing their cell walls in the middle lamella
Hemicellulose
a polysaccharide that strengthens the cell wall by cross-linking cellulose microfibrils
Lignin
a polymer that adds strength and stiffness to plant cell walls
Secondary cell wall
- laid down in some some specialised cells (e.g. xylem and sclerenchyma) inside the primary wall
- cells with secondary cell walls are usually long, and always flexible and strong
- therefore useful to humans as fibres such as flax and cotton
- thicker and impregnated with lignin, which makes it rigid and waterproof
Sclerenchyma function, location and adaptations
- provides structural support
- strengthens plants by making them stiffer and giving greater tensile strength
- have lignin deposited in cell walls for strength and waterproofing, no pits
- die once lignified, leaving behind a hollow fibre with end walls
- strength depends on length and degree of lignification
- located outside the vascular bundle in the stem
Xylem function, location and adaptations
- transports water and minerals in one direction only
- provides support by stiffening cell wall
- lignin provides support + waterproofing to long, hollow structure
- large lumen aids mass flow
- microfibrils help withstand tension
- pits for transfer of water between neighbouring xylems
- no cytoplasm or organelles to slow down flow of water
- found inside the stem on the inside layer of vascular bundle
Phloem function, location and adaptations
- transport of photosynthetic + growth products (e.g., glucose, proteins) from source to sink
- translocation can occur up and down the plant
- has sieve tubes specialised for transport
- perforations in sieve plates for material to pass through
- companion cells provide energy for active transport
- alive
- outside layer of vascular bundle between xylem and sclerenchyma
Importance of water to plants
- cohesion and adhesion and universal solvent - allows for transpiration and transportation of minerals and water in transpiration stream
- high specific heat capacity - temperature can be kept constant for organisms
- ice less dense than water - life can be supported under ice
Nitrates function
- nitrogen needed to make amino acids, which are needed for proteins for growth
- nitrogen needed to make DNA and ATP
Magnesium function
needed to make chlorophyll in leaves for absorption of light in photosynthesis
Calcium function
used to form calcium pectate, an important component of cell walls
Phloem and translocation - source
- sucrose and amino acids move into phloem with help from phloem parenchyma
- solute concentration in phloem increases
- water moves in from xylem, down water potential gradient
- hydrostatic pressure increases, aiding movement of water to an area of lower pressure
Phloem and translocation - sink
- solutes move out of phloem
- solute concentration in phloem decreases
- water moves back into xylem, down water potential gradient
- hydrostatic pressure decreased
William Withering - influence on modern drug development
- to treat dropsy, extract of foxglove can be used, which contains the drug digitalis
- observed that patients who had too much digitalis were poisoned, and too little digitalis had no effect
- by trial and error he came to know the right amount to give
Stages in modern drug development
- Pre-clinical testing
- Phase I: clinical trials
- Independent review of data
- Phase II: clinical trials
- Phase III: clinical trials
- after licensing
Pre-clinical testing
- animal studies
- lab studies on tissue culture
- modelling
- determining what the active ingredient is
Phase I of clinical trials
involves a small group of healthy individuals to determine how the body will react to the drug, the side effects of the drug and the correct dosage that should be taken
Phase II of clinical trials
will be done on a larger group of patients (non-healthy individuals who require the drug) to determine the effectiveness of the drug in treating the condition
Phase III of clinical trials
large patient group, use of placebo, patients randomly assigned to drug or placebo groups, double blind trials and statistical testing of the significance of results
Double blind trials
neither the participants nor the researcher knows what treatment the participants are receiving until the clinical trial is over
Placebo
an inactive substance that looks the same/is given in the say way as an active drug/treatment being tested
