Topic 4- Biodiversity and Natural Resources

Summary of topic 4

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  • Created by: R_Hall
  • Created on: 22-04-13 11:47

Adaptation and Evolution

  • Species- a group of organisms with similar morphology (features), behaviour and physiology, which can interbreed to produce fertile offspring, and are reproductively isolated from other species
  • A habitat is the place where an organism lives. Within a habitat, there can be many populations (a group of interbreeding individuals of the same species), which make up a community (various populations in an area)
  • Two species in the same habitat don't tend to be in competition- each species occupies a niche, which is the way an organism exploits its environment. If two organisms occupy the same niche (eg. same food source, time of feeding, shelter size) they will compete, and the better adapted organisms will dominate and exclude the other
  • Feature which enable organisms to survive are adaptions
  • Behavioural- Helps to survive and reproduce eg. agoutis bury Brazil nuts, it aids survival by providing a future food source
  • Physiological- Features of the internal workings of an organism, help to survive and reproduce. Thermophilous bacteria have heat stable enzymes, so can withstand 350c springs
  • Anatomical- Visible structure. Bumblebees have long tongues to collect nectar- food
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Natural Selection

  • Natural selection is the mechanism (first proposed by Darwin and Wallace) by which organisms change over to time as they adapt to a changing environment.
  • As a population grows, a greater proportion of individuals will die or fail to reproduce due to competition for resources
  • Individuals with a characteristic which gives them an advantage are more likely to survive. This is survival of the fittest
  • Evolution is a change in form (or behaviour or physiology) over generations. The new features gives an individual an advantage. It is defined as 'a change in allele frequency in a population over time'
  • For natural selection to lead to evolution, there must be some genetic diversity in a population
  • The ability of a population to adapt depends on 1. strength of selection pressure 2. size of gene 3. reproductive rate of organism
  • A gene pool consists of all the alleles of all the genes present in a population
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Biodiversity and Endemism

  • Biodiversity is the variety of life- the wealth of different species and the diversity within a species
  • Genetic diversity- the variation of inheritable characteristics within a species. The greater the variety of genotypes, the greater the genetic diversity. It allows the population to adapt to changing conditions
  • Genetic diversity arises from meiosis and random mutations. Some genetic differences show up in external phenotypes, but many have no visible effects
  • The simplest way to measure biodiversity is to count the number of species in a habitat- species richness. Doesn't take into account population size
  • A community where most of the species have similar abundances is said to have high evenness- has no dominant organisms
  • A diverse community would have high species richness and high species evenness
  • A place of high biodiversity is a biodiversity hotspot. The plant hotspot is in the Mediterranean Basin- contains 1/10 of Earth's plant species
  • Most are endemic- found only in that area
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  • All organisms are given a scientific name to avoid confusion between commonly used names for the same species
  • Carolus Linnaeus proposed a binomial system- a unique two part name. The 1st part- genus- is shared by all closely related species, and the 2nd defines the species in the genus
  • Placing organisms into groups based on shared features is classification or taxonomy. It results in a manageable number of categories.
  • There are 5 kingdoms in the taxon (series of nested groups). 1. Animalia (multicellular eukaryotes- heterotrophs-ingest) 2. Plantae (multicellular eukaryotes- autotrophs- absorb) 3. Fungi (multicellular eukaryotes- heterotrophs- absorb from decay)                 4. Protocista (eukaryotes- photosynthesise/feed) 5. Prokaryote (prokaryotes)
  • Members of a taxon will have the a common evolutionary ancestor
  • In 1960's, Carl Woese used RNA sequencing to classify bacterial species. In 1977, he found a group unlike the others- and he proposed it belonged to a new Archaea group. This formed the third branch of life- archaea, prokaryotes and eukaryotes- the three kingdoms
  • Initially the community was dubious- but eventually it was accepted
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  • Cellulose is the polysaccharide which gives plant cells strength. It is made up of beta-glucose
  • A condensation reaction between the -OH group on the 1st carbon of one glucose and the -OH on the 4th carbon on the adjacent glucose links the two molecules with a 1,4 glycosidic link
  • In cellulose, all the glycosidic links are 1,4, so it is a long unbranched molecule (no 1,9 links)
  • The straight chains of cellulose cause hydrogen bonds to form between the -OH groups in neighbouring cellulose chains, forming bundles called microfibrils, Individuallym the h bonds are weak, but the large no of them produces a strong structure
  • A plant cell wall is made of microfibrils wound together around the cell and stuck together with a polysaccharide glue. The glue is composed of hemicelluloses and pectin (which also are in the middle lamella-between cells- cementing cells together). This makes the cell wall very strong
  • Cell walls do not separate plant cells completely. Narrow fluid-filled channels (plasmodesmata), cross the walls so cytoplasm and substances can cross. Pits are areas where the cell wall is thin- aid movement of substances
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Plant Stem Structure

  • Xylem vessels- tubes for transport, and have a stiffened cell wall to support the plant
  • Sclerenchyma fibres- columns of cells with stiffened walls for support
  • Xylem vessels forms a column of cells acting as tubes for transport of water and mineral ions. They are waterproofed with lignin
  • The evaporation of water from the cells in the leaved provides the force needed to draw water up a plant. The stream of water passing through the plant is the transpiration stream
  • Energy for moving water up a plant comes from the Sun, which heats and evaporates the water. Water molecules are linked by cohesion and pulled up the xylem under tension- this is the cohesion-tension theory.
  • The movement of water through the xylem provides a mass flow system for transport of inorganic ions. They are absorbed into roots and are required throughout the plant
  • Nitrate ions- make amino acids for cytoplasm, chlorophyll, nucleic acids and ATP. Magnesium ions- for making chlorophyll. Calcium ions- healthy growth- structure of cell wall and permeability of cell membrane
  • Lignin is also needed to stiffen xylem vessels and sclerenchyma fibres. Strength depends upon length and degree of lignification. A turgid cell is full, and it presses on the cell wall to give support. If a cell loses water, it loses it's turgor
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  • Plant fibres are used to make clothing, ropes, paper and floor coverings. They are extracted by taking the plant apart (mechanically or by digesting surrounding tissue). Plant fibres can also absorb oil from polluted water, and make biodegradeable plastics
  • Starch is easy to extract, and has many uses. It can be used as a thickening agent, for stiffening fabrics, as a super-absorbant and as starch foam for packaging
  • Seeds are a rich source of vegetable oils. They can be used as fuels
  • The use of oil-based plastics and fuels is not sustainable as burning fossil fuels releases CO2, oil reserves are finite and plastics generate non-biodegradeable waste
  • The use of plant based products should help reduce these problems
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Drug Testing

  • In 1775, William Withering pioneered the use of foxgloves for the treatment of dropsy (now called oedema- accumulation of fluid in tissues). He made a 'digitalis soup' containing foxglove to a patient, who recovered, However, his next patient nearly died from treatment, causing Withering to give up. 
  • He moved to Birmingham General Hospital, where he conducted tests on 163 patients to determine dosage and side effects
  • Today a new drug must be tested thoroughly before it is sold and used-
  • 1. Pre-clinical testing- animal studies and laboratory studies on cells and tissues to asses safety and effectiveness against target tissue.
  • 2. Clinical trials- phase I- small group of healthy volunteers used to test dosage. Confirms whether the compound is being absorbed, distributed, metabolised and excreted as planned
  • 2. Clinical trials- phase II- small group of patients (100-300) are treated to look at effectiveness
  • 3. Clinical trials- phase III- large group of patients (1000-3000) are selected and divided into two groups. One is given the drug, and the other given a placebo. This is a double-blind randomised blind trial
  • 4. After licencing- trials to collect data on safety and effectiveness
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  • Today an important role of zoos is the successful breeding of animals through the captive breeding programme. It increases number of individuals in a species, maintains genetic diversity and allows animals to be re-introduced into the wild
  • Studbooks are used by zoos  to show the history and location of all inidviduals in a breeding programme. Provide raw data
  • Re-introduction is only possible if the habitat is intact
  • The Millenium Seed Bank was set up to conserve seed samples from threatened species of plants. The are kept in dry and cool conditions. Germination is tested every 10 years to make sure they are still alive
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