UNIT 2: DEVELOPMENT, PLANTS AND THE
TOPIC 4: BIODIVERSITY AND NATURAL RESOURCES
SPECIES• A SPECIES IS A GROUP OF SIMILAR ORGANISMS
WHICH ARE ABLE TO INTERBREED TO PRODUCE
• Species are reproductively isolated
• The gene pools of different species will not normally ever
• Every available habitat on Earth is colonised by living
organisms. Somewhere between 1.4 and 1.7 million
species have already been described and named.
• Endemic: A species that has evolved in one area and is
NICHES• Species occupy different niches. A niche is where an
organism lives and what it does; how it exploits its
• If two organisms share the same habitat, they will not
tend to compete as they will occupy different niches.
E.g. Barn Owls hunt at night whereas Kestrels hunt
in the day.
• If two organisms do occupy the same niche, the
better adapted one will survive at the expense (and
possible extinction) of the other. E.g. Red and Grey
• Biodiversity is made up of three factors; genetic, species and
ecosystem. It describes the variety and variability of life and the
habitats they depend on.
• Biodiversity: The variation of life on Earth
• Genetic Diversity: The number/variety of alleles in a
• Species Richness: The number of species within a certain area
• Ecological Diversity: The variety of habitats and environments
• Anatomical Adaptions: Adaptions to do with
• Physiological Adaptions: Adaptions to do with
how the animal works inside, and how body
• Behavioural Adaptions: Actions carried out
by organisms which help them survive or
• Natural selection is the mechanism, first proposed by
Darwin, by which organisms change over time as they
adapt to their changing environments.
• As a population increases in size, a greater proportion
of individuals will die or fail to reproduce owing to
competition for resources, such as food or space.
• This striving for survival is known as the ‘struggle for
SURVIVAL OF THE FITTEST
• In the struggle for existence there will be winners and
• Winners are the individuals who, by chance, possess some
characteristic which gives them an advantage over others.
• Winners have a select advantage over others, and are
more likely to survive and reproduce, passing on the
advantageous alleles to their offspring.
• Change in form, behaviour or physiology over generations
is called evolution.
EVOLUTION BY NATURAL
SELECTION• Evolution = “a change in allele frequency in a population
over time (generations)”.
• For natural selection to lead to evolution, there must be
some genetic variation in the population.
• An allele can be selectively neutral (i.e. it has no advantage
or disadvantage) but suddenly can become selectively very
advantageous if and when the environment changes.
• A modern example of natural selection is headline becoming
resistant to head lice shampoos, therefore most headline
survive and quickly breed the next resistant generation.
BEING ADAPTABLE• The ability of a population to adapt to new conditions will
- The strength of the selection pressure
- The size of the gene pool
- The reproductive rate of the organism
• Selection pressure: Selective pressure is any phenomena
which alters the behaviour and fitness of living organisms
within a given environment. The reason why an allele is
favoured over others.
• The current rate of climate change due to global warming is an
example of selection pressure. Some organisms will survive
and some will not.
• A gene pool consists of all the alleles of all the genes present in
• Some alleles of each gene will be common in the gene pool and
some will be rare.
• Populations with a bigger gene pool (more different alleles of
each gene) are said to have greater genetic diversity.
• New alleles are produced all the time by mutation of existing
alleles, but this is a slow and random process.
• When the population of a species declines too far, some alleles
are lost, and the genetic diversity of the species declines.
A HIERARCHICAL SYSTEM
• Kingdom Phylum Class Order Family Genus
• Placing organisms into groups based on shared
features, known as classification or taxonomy,
results in a manageable number of categories
and has been the principle aim of all
• All organisms are given a scientific name, for example, Arum maculatum.
• The binomial system is a system in which each species was given a unique
two-part Latin name.
• The binomial system is still in use today.
• The first part of the name, the genus, is shared by all closely related species,
so all horses and zebras are in the genus Equus.
• The second part of the name defines the particular species in the genus.
• Together these two words make up a unique species name that is often highly
• The binomial system is universal, as it is used and recognised by all scientists
all over the world.
WOESE’S THREE DOMAINS• In the 1960s, a scientists called Carl Woese aimed to define the evolutionary
relationships of prokaryotes.
• He pioneered RNA sequencing of bacteria
• A decade later he noticed that one complete group of bacteria, the methanogens,
completely lacked the sequences characteristic of bacteria.
• He supported his ideas with additional evidence, for example the methanogens, unlike
other bacteria, had no peptidoglycans in their walls.
• Woese proposed that this group belongs to a new category of organisms, the Archaea.
Today they survive in extreme anaerobic environments, such as hot springs.
• A paper published in a scientific journal announced the new group, allowing the theory to
be peer reviewed.
• At first the scientific community was sceptical and dismissed Woese’s theory, but after
the influential microbiologists Otto Kandler accepted his work and organised the world’s
first Archaea conference in 1981, the scientific community slowly but surely started to
accept the theory and recognised it’s full significance.
BIODIVERSITY WITHIN A
• Individuals within a species differ from one another - they
• In all organisms that reproduce sexually, every individual has
a unique combination of alleles (except identical twins and
• This is genetic diversity, and the greater the variety of
genotypes, the more genetically diverse the population.
• Genetic diversity allows the population to adapt to changing
conditions so it should be conserved.
SOURCES OF GENETIC
• Meiosis: crossing over and independent assortment
• Random mutations: changing the DNA sequence (alternation,
insertion, deletion), creating new alleles.
• Most mutations have no effect on the phenotype, some have
harmful effects and some are beneficial.
• Fertilisation: fusion of genetic material from two individuals;
• Genotype: dominant alleles mask recessive ones
PLANT CELLS• Plant cells have a cellulose cell wall - something that animal cells do
• They have a cell membrane, a nucleus and a nucleolus, just like an
animal cell codes
• They have a large sap-filled vacuole, surrounded by a tonoplast
• In the cytoplasm, they contain all the organelles that animal cells have,
except centrioles, and plus chloroplasts
CHLOROPLASTS• Chloroplasts are the site of photosynthesis in
plant cells. Only plant cells contain
• Chloroplasts also contain circular DNA and
small 70s ribosomes.
PLANT CELL WALL• The golgi apparatus produces vesicles which contain components for
the new dividing cell wall. The vesicles congregate in the middle of
• The first layer to be laid down is calcium pectate which forms the
• The next layer is a a layer of cellulose which forms the primary cell
• A second layer of cellulose may be added, forming the secondary
• Further layers of lignin may be added.
• There are holes that go through the entire cell wall, which are called
plasmodesmata, through which the cytoplasm of one cell connects
with it’s neighbouring cell.
• A pit is a hole in the secondary cell wall through which water can
STARCH• Starch is made from two polymers of glucose, amylose and
• It is made up of alpha-glucose (α-glucose)
• Amylose is a chain of thousands of glucose units. Amylopectin is
a branched chain of glucose molecules with 1,6 and 1,4 glycosidic
• It is a storage polysaccharide found in green plants, such as
potatoes, rice, cereals ect.
• Starch is large, insoluble and it doesn't have an osmotic effect.
• We eat starch as it is a great source of energy; we break it down
into glucose monomers (single sugar units).
• Cellulose is the most abundant polymer on Earth.
• It is made up of beta-glucose (β-glucose)
• It is a polysaccharide
• All bonds are 1,4, therefore cellulose is a long, unbranded molecule.
• Hydrogen bonds form between the -OH groups in neighbouring
cellulose chains, forming bundles called microfibrils.
• The large number of hydrogen bonds in the microfibril produces a
• Therefore the arrangement of the cellulose microfibrils in the cell wall
makes it very strong but flexible.
PLANT FIBRES• Plants contain fibres in their stems, leaves and roots.
• Fibres are specialised cells which have been thickened in
their cell walls so that they can carry out particular
• Two examples of fibres are sclerenchyma and xylem.
• Humans use fibres to make products such as clothing,
paper, rope and many more. They are used as they are
long and thin, flexible and strong.
• Plant fibres are also used to absorb heavy metals, absorb
hydrocarbons from polluted water, and they can be added
USES OF PLANT FIBRES
• Hemp: Fibres from stem and leaf = matting, rope, coarse cloth
• Cotton: Fibres on cotton seed aid seed dispersal. We use cotton as
fabric. Long, thin and flexible, but strong.
• Linin: Flax plant/fibres from stem = clothing, fabric.
• Straw: Hats, baskets, thatching, building materials.
• Wood: Xylem vessel = furniture, building material. Strength is
important, density, hardness.
• Coir: Fibres from coconut husks = matting
WATER TRANSPORT IN
1. Water uptake in the roots:
- As water moves up the xylem, it causes a low conc. of water in the
cells of the root
- There is a high conc. of water in the soil
- Water therefore moves into the root through the root hairs by osmosis
2. Water moves as a continuous column in the xylem vessels:
- When water enters the root hair it travels into the xylem vessels in the
root, then into the xylem in the stem and leaves
- Adhesion between water molecules and the cellulose in the xylem
vessel. Greater the force, the further up the xylem the water moves.
3. Transpiration stream draws water up through the plant as it transpires from
- Water on the surface of the leaf cells evaporates into the air spaces in
- This water then moves out of the leaf through the stomata by
• Mineral ions are present in the water in the soil. They will enter the
plant through the cell roots by active transport. They will travel to
cells in the plant via the xylem vessels.
• Nitrates: They are a source of nitrogen, essential for the plant to
be able to make amino acids (for proteins) and nucleic acids (for
• Magnesium: It’s essential for the synthesis of the green pigment
chlorophyll (found in chloroplasts) and is used in photosynthesis.
• Calcium: Calcium is essential for the production of the middle
lamella (made of calcium pectate) when the cell divides.
• Plants sometimes store toxic compounds in hairs on the surface of their
• These chemicals are toxic to microbes and some insects, but some are
attractive to us as flavouring in foods or tea (e.g. mint)
• Garlic extracts have been found to destroy bacteria which cause intestinal
infections. This is potentially important as some strains of the bacteria are now
resistant to widely used antibiotics such as penicillin.
• The active ingredient in garlic is allicin; it interferes with lipid synthesis and
RNA production. Allicin is only produced when the plant is cut or damaged.
• Some studies have shown that some parts of a plant tend to have greater
antibacterial properties than the rest. These are typically the seed coat, fruit
coat, bulb and roots.
MEDICINES FROM PLANTS
• Many plants contain poisons, or produce them rapidly as a response
• However, ‘poison’ is a relative term and relates to the dosage
necessary to cause harm to an organism.
• Clearly if a chemical can kill pathogenic microbes or malignant cancer
cells at a dose level which leaves humans alive, then this ‘poison’ is
more likely medicine.
• An enormous number of medicines are derived from chemicals
originally discovered in plants.
• 75-80% of the world’s population uses extracts from plants as
FOXGLOVE AND DROPSY
• Foxglove leaves are poisonous when eaten by humans and other animals. They have a
strong, bitter taste which serves as a warning.
• The symptoms are dizziness, vomiting, hallucinations and heart failure.
• It is a traditional folk remedy when used in moderation. It has been known for its medicinal
qualities for centuries, and in particular it was used to treat a condition called dropsy.
• Dropsy is when fluid accumulates in the body tissues, and is very painful and can cause a
• William Withering investigated the medicinal properties of foxglove, and it became an
accepted form of medicine after he published A Treatise on the Foxglove in 1775.
• He realised that getting the dose right for the patient was of vital importance. He applied a
standard procedure to discover the correct dosage for each patient.
• He helped change the face of medical practice forever.
DRUG TESTING TODAY
• Today, a potential new drug must pass a series of tests if it is to be developed
into a new product. It has to be proven to be effective, safe and capable of
making a profit. It can typically take 10-12 years and cost over US$1 billion to
develop a new drug.
1. Pre-clinical testing: Animal and laboratory studies on isolated cells and tissue
2. Clinical trials - phase I: A small group of healthy volunteers are given different
3. Clinical trials - phase II: Small groups of patient volunteers (100-300)
4. Clinical trials - phase III: Large group of patients (1000-3000) split into two
groups. One group receives a placebo, one group receives the drug.
5. After licensing: Trials continue to collect data about the safety and
WHAT’S IN A SEED?• In flowering plants, the ovule is fertilised by the nucleus from a pollen grain and
develops into the seed.
• The outer layers of the ovule become lignified forming a tough seed coat which protects
the embryo within the seed.
• In many monocotyledons, the stored food in the seed remains outside the embryo in
storage tissue called endosperm. Seeds of this type are called endospermic.
• In many dicotyledons the embryo absorbs the nutrients from the embryo and the food is
stored in the seed leaves (cotyledons) which swell to fill the seed.
• In some seeds, food is stored in the hypocotyls - the developing stalk.
• When conditions are suitable, the seed takes in water through a small pore in the seed
coat. Water triggers metabolic changes in the seed. Production of plant growth
substances is switched on and these cause the secretion of enzymes that mobilise the
stored food reserves. Starch is broken down into glucose which is converted to sucrose
for transport to the radicle and plumule. Proteases break down the proteins in the food
store to give amino acids, and lipases break down the stored lipids to give glycerol and
• Seeds come in all shapes and sizes, most of
which are appropriate for wide dispersal.
• Dispersal helps offspring to avoid competing with
their parent plant or with each other.
USES OF STARCH FROM
• Thickening: when starch granules are heated in water they suddenly swell,
absorb water and thicken the liquid. Custard and wallpaper paste.
• Stiffening fabrics: Starch mixture applied to surface is gelatinised and then
cooled, allowing bonds to form between the starch molecules. Paper coatings
and cloth treatments. Adding water reverses the process.
• Super-absorbents: When starch is chemically crossed-linked before it is
gelatinised, particles are formed which can be dried. When rehydrated, they
take up a lot of water. Nappies.
• Starch foam: When the pressure at which starch is being gelatinised is
suddenly raised, then released, steam forms and the starch ‘puffs’ into an
expanded structure. Organic packaging, rather than plastics or polystyrene.
USES OF VEGETABLE OILS
• Fuels: Biodiesel produced today can be used in
unmodified diesel engines alternating with petroleum
• It produces less sulphur dioxide than diesel, and less
• It is possible to make biodiesel from waste vegetable
cooking oil, or from oil crops such as rapeseed.
• It is available as 100% biodiesel or a blend with fossil
SUSTAINABILITY• Burning oil-based fossil fuels releases carbon dioxide into the
atmosphere, contributing to global warming.
• Oil reserves will eventually run out.
• Plastics generate non-biodegradable waste, creating major waste
• The use of plant-based products should help to reduce these problems,
although burning fuel made from vegetable oil still releases carbon
• We need to consider the source of the plant product, and the energy
used and pollution created during the production and transportation of
• Plant based plastic bags is a more sustainable alternative to plastic
bags than paper bags.
• Zoos have an important role in the successful breeding of
animals in their care.
• Increasing the number of individuals of the species if
numbers are very low
• Maintaining genetic diversity within the captive population
• Reintroducing the animals into the wild if possible
• There are more than 400 zoos in Europe participating.
HOW GENETIC VARIATION IS
• Genetic Drift: In a small population, some of the alleles may not
get passed on to offspring purely by chance. This change in the
allele frequencies over time is known as genetic drift, and leads to
a reduction in genetic variation.
• Inbreeding depression: In a small population, the likelihood of
closely related individuals mating increases. This inbreeding
causes the frequency of homozygous genotypes to rise, with the
loss of hetrozygotes. Inbreeding results in offspring inheriting
recessive alleles from both parents. Many recessive alleles have
harmful effects so inbreeding depression results. The offspring are
less fit, they may be smaller, less likely to survive and reproduce
and females may produce fewer eggs.
• Keeping studbooks: provide the raw data upon
which all the breeding plans are based. Shows the
history and location of all of the captive animals of
that species in the places where they are co-
operating in an overall breeding programme.
• Individuals who breed poorly in captivity must be
encouraged to breed, whilst those who are
particularly good breeders must be limited in their
THE MILLENNIUM SEED BANK
• The aim of the MSB is to conserve seed samples from threatened species of plants, with
10000 species already banked.
• Seeds are collected from all around the world.
• Most seeds are small and easy to store, and many plants produce large amounts of
seeds, so collecting small samples is unlikely to harm a wild population.
• Seed preservation is improving all the time as more research is carried out. Seeds
survive longer if kept cool and dry.
• Once the seeds identification has been verified, and they have been cleaned and dried,
the seeds are stored at -20ºC.
• After a month of the seeds being stored, they are taken out to be tested and germinated
to ensure they can survive in the preservation conditions. Germination is then tested
about every 10 years.