Biology topic 4

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Definitions

Species: A species is a group of organisms with SIMILAR FEATURES that can INTERBREED to produce FERTILE OFFSPRING.
Niches: an organism occupies a niche within it's habitat, this will be how it INTERACTS with the other organisms in that habitat and also the environmental conditions. No two species occupy the same niche within a habitat. One species would always OUTCOMPETE the other species.
Adaptation: A feature which enables an organism to SURVIVE. There are three catagories- BEHAVIOURAL, PHYSIOLOGICAL and ANATOMICAL.
Natural selection: the mechanism by which organisms CHANGE OVER TIME as they ADAPT to their environment.
Evolution: A change in ALLELE FREQUENCY in a POPULATION OVER TIME.
Selection pressure: Any cause which REDUCES REPRODUCTIVE SUCCESS e.g. Drought, Disease, Change in environment.
Gene pool: All the ALLELES present in a POPULATION.
An endemic species: A species that ONLY occurs in that ONE LOCATION and nowhere else.
A dominant organism: Is the MOST COMMON SPECIES in a habitat.
Biodiversity: the VARIETY of LIFE and SPECIES. The DIVERSITY within ECOSYSTEMS.

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Evolution by natural selection

1. A population contains genetic variation caused by mutations.

2. Organisms produce more offspring than can survive and reproduce.

3. A change in environment causes a selection pressure.

4. Intra-specific competition occurs (competition within a species).

5. An allele with no previous advantage now becomes favourable.

6. Organisms with this advantageous allel are more likely to survive and reproduce- "survival of the fittest".

7. Advantageous allele passed on to offspring.

8. Overtime the advantageous allele frequency will increase in the gene pool and others may become less frequent.

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Measuring biodiversity

1. Species richness: The number of DIFFERENT species present in a HABITAT.
Advantages- Quick, Cheap and simple.
Disadvantages- Takes no account of population size of each species and can give misleading information about biodiversity.

2. Species evenness: Measures the NUMBER of different species and the POPULATION SIZE of each SPECIES.
The community in which most species have similar abundance shows high species evenness i.e. No dominant (core) species. High species evenness= Higher diversity.

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Biodiversity hotspots

Some areas of the Earth have unexpectedly high levels of PLANT BIODIVERSITY e.g. The Mediterranean Basin.

A biodiversity hotspot: Is a region with MORE THAN 1250 different PLANT SPECIES and 0.5% or more of the TOTAL GLOBAL PLANT DIVERSITY present as ENDEMIC species.

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Genetic Diversity

Genetic diversity: The variety of ALLELES in a GENE POOL.

Populations require HIGH genetic diversity to ADAPT to CHANGING CONDITIONS.

Measured by: DNA sequencing (Direct method), Gel electrophoresis (seperates fragments of DNA based on length).

Apply data: Used in a heterozygosity index (is a proportion or % of genes which are present in the heterozygous form). A higher heterozygosity index number indicates more genetic diversity (more genes occur in genetic form, 2 alleles for every heterozygous, only one for homozygous).

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Genetic diversity 2

Sources of genetic variation:

Gene (point) mutations: Alterations of the DNA base seqeunce. May arise during DNA REPLICATION or another stage of the cell cycle. Sometimes the WRONG NUCLEOTIDE will slot in by mistake.

Chromosome mutations: Some small sections of chromosome may be REARRANGED during MEIOSIS, they may be MOVED from one chromosome to another or even LOST ALTOGETHER.

Independent assortment: Each homologus pair of chromosomes is SORTED INDEPENDENTLY of the others during MEIOSIS and the process is RANDOM.

Crossing over: New combinations of alleles result when PIECES of GENETIC MATERIAL are EXCHANGED between HOMOLOGOUS chromosomes during Meiosis.

Mate selection: Different combinations of alleles will come together in offspring depending on which two parents come together. Conservationists can increase genetic diversity by selecting which pairs of animals (or plants) will mate. STUDBOOKS help to make the BEST MATE SELECTION.

Random fertilisation: Different combinations of alleles will come together in the offspring depending on the SPERM and the EGG involved in the fertilisation.

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Naming

Carolus Linnaeus- The BINOMIAL SYSTEM

  • Each organism has a SPECIFIC NAME
    Binomial- TWO NAMES, a GENUS name and a SPECIES name.
  • ALWAYS type in ITALICS or UNDERLINE if handwritten.
    Genus name always has a capital letter, species name does not.
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Taxonomy

The scientific study of grouping of organisms is CLASSIFICATION.
Putting organisms into HIERARCHICAL TAXA (groups) is TAXONOMY.
LIFE
DOMAIN
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES

KINGDOM:
ANIMALIA- Multicellular EUKARYOTES that are HETEROTROPHS.
PLANTA- Multicellular EUKARYOTES that are AUTOTROPHS.
FUNGI- Multicellular EUKARYOTES that are HETEROTROPHS, ABSORB nutrients from DECAYING matter after EXTERNAL DIGESTION.
PROTOCTISTA- EUKARYOTES that PHOTOSYNTHESISE or feed on ORGANIC MATTER from other sources but are NOT INCLUDED IN OTHER KINGDOMS.
PROKARYOTE- BACTERIA and BLUE GREEN BACTERIA (CYNOBACTERIA).

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New technology

Scientists could now study organisms on a molecular leve e.g. DNA sequencing.
Molecular phylogeny: Compares different molecules to IDENTIFY EVOLUTIONARY RELATIONSHIPS (used to produce phylogenetic trees).
The more similar in structure a molecule is, the more closely related the organisms are.
Changes in molecules (mutations) happen at a STANDARD RATE, so TIMES when SPECIES DIVERGED can be ESTIMATED.
Phylogenetic tree- shows EVOLUTIONARY RELATIONSHIPS based on MOLECULAR DIFFERENCES.

New theory of classification: THE THREE DOMAINS
1. Bacteria
2. Archaea
3. Eukaryota

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Scientific process and role of critical evaluation

When a new theory is proposed:

Publish a paper in a scientific journal- peer reviewed (evaluate methods and results- carry out similar work to collect evidence to support theory).

Present information at a symposium with similar scientists.

Publish on the internet.

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Plant cells

Cell wall: CELLULOSE, fully permeable, it is used for structure and support

Middle lamella: PECTIN, sticks plant cells together, giving STABILITY.

Plasmodesmata: channels in the cell wall for TRANSPORT BETWEEN CELLS.

Pit: have to be in PAIRS (one on either side), areas of very thin cell wall For TRANSPORT between cells. Over time a pit might become a plasmodesmata.

Amyloplast: STARCH STORAGE. It is a membrane bound organelle.

Chloroplast: site of PHOTOSYNTHESIS.

Vacuolar membrane (TONOPLAST): semi permeable membrane surrounding the vacuole, controls what enters and leaves the vacuole.

Vacuole: membrane bound organelle that contains CELL SAP and gives the cell structure.

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Cellulose structure

Plant cell walls.
Slow decomposition rate.
Mechanically it is very STRONG.
Polymer of BETA GLUCOSE.
C1-4 GLYCOSIDIC LINKS
To form these links alternate glucose molecules flip through 180 degrees (INVERT).
Side groups stick out in alternate directions.
H bonds form and cross link the chains.

70 CROSS LINKED BETA GLUCOSE CHAINS COMBINE TO FORM A MICROFIBRIL.
Lots of microfibrils are held together to form FIBRES. Layers of fibres are laid down at different angles in HEMICELLULOSES and PECTINS which act as GLUE.

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Use of plant fibres and starch and Sustainability

Sustainability: the use of resources that meets the CURRENT NEEDS WITHOUT DEPLETING them for the use of future generations.
Current unsustainable practices:
1. Burning oil-based fossil fuels- fossil fuels are a NON-RENEWABLE resource. They release CO2 (GREENHOUSE GAS) which contributes to GLOBAL WARMING.
2. Using oil-based plastics- generates NON-BIODEGRADABLE WASTE. Also oil reserves are NON-RENEWABLE.
Plant resources and sustainability:
Plants can provide RENEWABLE resources e.g. Strach and plant fibres. Renewable resources are natural and are replenished. The use of these renewable sources is sustainable.
1.Starch- BIODEGRADABLE PLASTICS, starch from seeds can be used to provide sugars for fermentation to produce alcohol for biofuels. Starch can be usedin adhesives, paints, toiletries, nappies, 'sizing' of paper or cloth and packaging.
2. Plant fibres- Made of Xylem and Sclerenchyma (cellulose and lignin). They are LONG, FLEXIBLE, STRONG and RESISTANT TO DECAY. For example: rope, textiles, biocomposites- composit resin mixed with fibres, building materials. Plant fibres must be pulled out or soft tissue must bebroken down (retting).
3. Oils- vegetable oils can be used to REPLACE FOSSIL FUELS. Oils from crops such as rapeseed can be used as a biofuel.

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Advantages + Diadvantages of using plant resources

Advantages:

RENEWABLE.
Land unsuitable for agriculture can be used.
Less plastics therefore less space needed for landfill.
CARBON NEUTRAL.
Less oil used means less loss of oil reserves.

Disadvantages:

Land used is replacing rainforests and agricultural land.
Current uncultivated land may not be suitable.
Loss of wildlife habitats.
LOWER QUALITY PRODUCTS.
Fossil fuels used in manufactor, transport or growth produces CO2.

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Seedbanks

Plants need to be conserved because:

-Habitat destruction
-Climate change
-Over Harvesting
-Future use
-Maintain diversity

Seed storage- ex situ
Most plant produce LOTS OF SEEDS.
Seeds are SMALL and easy to store.
SURVIVED DESSICATED FOR MANY YEARS (dry conditions).
Store at -20*C to increas life span (enzymes are unable to work at these temperatures).
After 1 month GERMINATION IS CHECKED. Germination tested every 10 years: if <75%, the seed are grown to collect new seed sample (as some could not germinate).

Millennium seed-bank
Aims to collect seed samples from 10% of the world's seed plants by 2010.

  • Criteria for seed selection: ECONOMIC, ENDANGERED, ENDEMIC.
    Used for research, habitat restoration and species reintroduction.
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Advantages and Disadvantages of Seedbanks

Advantages:

Cheaper than storing plants.
Large numbers as they need less space.
Less work.
Less workforce.
Stored anywhere cool enough.
Less susceptible to disease, vandalism and natural disaster.

Disadvantages:

Testing for viability (see if the inside of the seed is still living) is expensive and time consuming.
Too expensive to store and test all seeds.
Difficult to collect some seeds from remote locations.

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