Topic 4: Biodiversity and Natural resources


Threat of human activity

Biodiversity is the variety of living organism which includes species diversity (different species and the abundance of each species within a space) and genetic diversty (variation of alleles within a species)

Endemism is when a species is unique to a single place

Natural selection leads to adaptation and evolution has increased biodiversity. Human activities, such as farming and deforestation are reducing species diversity - causing biodivesity to fall.

Conservation is needed to maintain biodiversity. It is also really important for endemic species as they are vulnerable to extinction.

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Measuring Diversity

Diversity can be calculated by counting the number of different species within an area or the number of different species as well as the number of individuals within the species.

To calculate a random sample should be selected and recorded using a quadrat,  a sweepnet, pitfall trap, or a net.

Genetic diversity - phenotypes and genotypes. Exploring phenotypes will show us the different alleles. The larger the amount of phenotypes, the greater the genetic diversity. Looking at genotypes, DNA can be extracted and analysed for sequence of bases as these will differ across alleles. The greater the different numer of alleles, the greater the genetic diversity

Heterozygosity index:

H= Number of heterozygotes

     Number of individuals in the population



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Niche and adaptions

A niche is the role a species has within an environment (where it lives and what it does there). Every species has a unique niche e.g. Common pipistrelle bat and soprano pipistrelle bat live in different places and use different frequencies but eat the same food

Organisms can be adpated to their nche in 3 ways:

Behavioural adaptation - Ways that organisms act to increase their chance of survival e.g possums play dead to escape attack, scorpions dance before mating

Physiological adaptation - Processes inside the body to increase survival e.g brown bears hibernate over winter to save metabolic energy, some bacteria produce antibiotics to kill other types of bacteria

Anatomical adaption - Strcutural features that increase survival e.g otters have a streamlined shape to glide through the water, wales have a thick layer of fat

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Natural selection

Mutations can increase the number of alleles in the population, so individuals show variation within their phenotypes. Some of these characterstics will make an individual more likely to survive.

Selection pressures such as predation, disease and competition create a struggle for survival.

Individuals without the advantageous alleles dont survive which means there are fewer individuals for cometition for space and resources

Individuals with advantageous alleles become more likely to survive and reproduce and pass on useful alleles to offspring

Over generations, this leads to evolution as the frequency of advantageous alleles in the population increase and the adaptions become more common

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Hardy Weinbur Principle

How often an allele occurs within a population is called allele frequency. The frequency changes over time as organisms evolve. The hardy-weinburg equation predicts the frequencies of alleles within the population won't change from one generation to the next.

Predicting allele frequency...

p+q=1 where p is the frequency of dominant alleles and q is the frequency of recessive alleles.

Predicting genotype and phenotype frequency...

p2+2pq+q2=1 where p2 is the frequency of homozygous dominant genotype, 2pq is the frequency of heterozygous genotype, q2 is the frequency of homozygous recessive genotype.

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Taxonomy is the science of classifying organism. We organise them into groups depending on their similarities and differences. There are 8 leveled groups for them to be organised into: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. This classification is based on an organism's phenotype and genotype.

New data about a species can influence the way that it is classified. A new three domain classification system has been proposed based on new data. The data came from molecular phylogeny which studies evolutionary history of organisms. Organisms that were within prokaryotae have been seperated into bacteria and archaea. Organisms from the other 4 kingdoms remain in Eukaryota. They were reclassified as phylogeny found that archaea and bactreria were less similar interms of genotypes than thought before.

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Plant cells structure

Cell wall - provides support

Midlde lamella - Acts as an adhesive to stick plant cells together. Can also provide stability.

Plasmodesmata - Allows transport of substances and communication between cells

Pits - Allow transport of substances across cells

Chloroplast - The site where photosynthesis occurs

Amyloplast - Storage of starch grains

Vacuole and Tonoplast - Contains cell sap  and keeps the cell turgid. Breaks down unwanted chemicals. Tonoplast controls what goes in and out of the cell.

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Starch - The main energy store in plants. Cells get energy from glucose and excess glucose is stored as starch. When it needs more glucose, it converts starch back into glucose. Starch is a mixture of amylopectin (branched) and amylose (Unbranched).

Cellulose is a major component of cell walls in plants. It is made of long unbranched chains of b-glucose. Between 50-80 cellulose chains are linked together by a large number of hydrogen bonds to form strong threads called microfibrils.

Plant fibres are made up of long tubes of plant cells. They are strong due to the arrangement of cellulose microfibrils in a net-like arrangement. Also, strength can be provided by a secondary cell wall which forms after the plant finishes growing. The secondary cell wall is stronger as it contains alot more lignin.

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Use of plant fibres by humans

Using plant fibres and starch can contribute to sustainability.

Plant fibres - Ropes and fabrics made out of plant fibres are more sustainable that the use of plastics. Less fossil fuels are used and crops can be regrown to maintain the supply for generations. These products are also biodegradable and are cheap and easy to grow.

Starch - Found in all plants. Can be used to make a type of plastic called bioplastics that dont contain any oil. This is more sustainable as the starch can be recreated through plants. Vehicle fuel can also be created using bioethanol.

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Identify sclerenchyma fibres, phloem sieve tubes a

Use a scaple to cut a cross section of the stem. Pick up the cross section and place in water until you are ready to use them as it stops the cell drying out. Transfer the section to a dish containing toluidine blue and leave for a minute so that the lignin is stained blue. This makes it easier to view the sclerenchyma and xylem. The phloem will appear purple. Rinse off the water and mount the section onto a slide. Place under a microscope and create a labelled drawing until you get a clear image.

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Plant stems

Xylem Vessels

Xylem has a function of transporting water around the plant and provide support. They are long tubes made up of dead cells joined end to end. They are found together in bundles. They have no end walls which makes a long uninterrupted tube. Cell wall is thickened with lignin to provide support.


These provide support and play no role in the transport. They are also made up of bundles of dead cells, but do have end walls. They contain lots of glucose and are thickened with lignin


These have a role of transporting organic substances (known as translocation). Phloem contain two types of cells phloem sieve cells and companion cells. Sieve tubes are the end walls that have lots of holes to allow solutes to pass through them. They have no nucleus so camnnot survive by themselves, hence the use of the companion cells. Companion cells carry out all living functions for both of them

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Importance of water and inorganic ions

Plants need water and inorganic ions for a number of different functions. They are absorbed through the root and transported up the cell. When plants lack water and mineral ions they show deficiency symptoms

Water is needed for photosynthesis, to transport minerals, to maintain structural rigidity and to regulate temperature

Magnesium ions are needed for the production of chlorophyll

Nitrate ions are needed for the production of DNA, proteins snd chlorophyll. They are also needed for fruit production, plant growth and seed production.

Calcium ions are important components in cell walls. They are needed for plant growth

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Investigate plant mineral deficiencies

Make up 5 nutrient broths, one containing no calcium, one containing no nitrate, one containing no magnesium, one containing none and one containing all three.

15 seedlings (3 for each concentration) from the same plant of the same age, measure the mass using a balance and record.

Cover the test tube with cling film and pierce the top with scissors. Place the shoot in the gap so that the root is inside the nutrient solution.

Leave to grow for 2 weeks and observe the growth. Record colour changes and heights. Remeasure the mass using a balance.

Use pictures to add to the experiment notes

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Determine the tensile strength of plant fibres

Attach the fibre to a clamp stand and hang a weight from the other end. Keep adding weights unti lthe fibres break.

Record the mass needed to break the fibres. The higher the mass, the higher the tensile strength.

Repeat this experiment with different samples of the same fibre to calculate a mean and rule out random error.

Fibres being tested should always be the same length.

Temperature and humidity should be kept constant

Use safety measures e.g wear goggles

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Drug testing

William Withering is famous for trialling and recording the use of digitalis leaves. A patient would be given digitalis preparation, and the effect on the patient would be recorded (including symptoms of overdose, effect on condition and the final result) as a cure for dropsy as the leaves contain digitalin. He slowly increased doses until it tackled dropsy effectively.

Drg testing today-

Preclinical testing: Animal and lab studies on whether it is effective at tackling the disease

Clinical trials phase 1: Small groups of volunteers are given doses. The majority of the time, the volunterrs are healthy. Trails confirm how it is passing through the body.

Clinical trials phase 2: Small groups of volunteers (100-300) are treated to look at the drug effectiveness.

Clincial trials phase 3: Large groups of patients (1000-3000) are selected and divided into 2. One group is given the compound investigated, the second an inactive placebo. These trials will be double blind.

After licencing: Trails continues to ensure effectiveness and safety.

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Bacterial growth

Bacteria need a source of nutrients so they can respire and grow.

If they rely on aerobic respiration, they'll need a supply of oxygen too.

The temperature and pH of the environment are also important. If too high or too lowit can affect enzyme activity meaning metabolic activity cant take place normally

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Investigate antimicrobial properties of plants

use aseptic technique throughout to prevent the growth of harmful bacteria.

Use a sterile pipette to add the bacteria culture onto the agar plate onluy slightly opening the lid. Use a spreader to evenly spread the bacteria across the whole plate reaching all the edges.

Place paper disks into the garlic and mint solutions and leave to soak for 15 minutes. Remove the disks with forceps, being careflu not to expell the solution and place on the agar disk equal distances from each other and the edges.

Place the lid on and close with 4 pieces of hazard tape. Label with a marker pen, whether that plate was garlic or mint.

Incubate at a maximum of 25 degrees for 24-48 hours.

Take the plate with the lid still on and measure the clear zones formed for each disk using a ruler to measure a diameter or graph paper soaked on acetate.

Should then be safely disposed of by an autoclove to burn all the bacteria

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Zoos and seed banks

Zoos and seed banks help to conserve endangered species. This occurs to prevent a reduction of biodiversity. Conservation involves the protection and management of endangered species.

Zoos and seedbanks help conserve these species.

Seedbanks store seeds of endangered plants. If a plant becomes extinct in the wild, seedbanks can regrow new plants. They also help genetic diversity by storing seeds with a range of characteristics.

Zoos have captive breeding programmes to help endangered species. They breed together in zoos to keep the numbers up.

Reintroduction intp the wild can bring species back from the brink of extinction. It can also help to restore habitats. However, it can also introduce new diseases to the wild and change natural behaviour.

This can be used to help educate people as we raise awareness of conserving species and the levels of biodiversity.

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