Biology Unit 2

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Interspecific variation
Variation between different species
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Intraspecific variation
Variation with a species
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Alleles
Different versions of the same gene
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Phenotype
Appearance of an individual
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Genetic variation factors
Diffenent alleles means different genotype which means different phenotype
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What is DNA made from?
Lots of nucleotides joined together
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What are nucleotides made from?
A pentose sugar, a phosphate group and a nitrogenous base
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What are the 4 possible bases?
Adenine, thymine, cytosine, guanine
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How does DNA join up?
Phosphate group of one nucleotide joins with the pentose sugar of another forming a polynucleotide strand. Two polynucleotide strands join by hydrogen bonds between complimentary bases (specific base pairing)
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Specific Base Pairing
A always pairs with T and G always pairs with C
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How does the structure of DNA help its function?
Contains the genetic information to grow and develop a zygote. DNA molecules can coil up to fit inside the cell nucleus. Paired structure is easy to copy itself during self-replication. Double helix structure is very stable in the cell
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How is DNA stored in Eukaryotic organisms?
It winds up around histone proteins to form a chromosome
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How is DNA stored in Prokaryotic organisms?
It condenses to fit in the cell by supercoiling
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Triplet Code
Where 3 bases code for 1 amino acid
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Introns
Sections of DNA that don't code for amino acids
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Exons
Sections of DNA that code for amino acids
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Homologous pair of chromosomes
Chromosomes that are the same size and contain the same genes
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Mutation
Change in the base sequence of an organism's DNA
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Meiosis
Forms 4 genetically different haploids from one diploid mother cell
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Crossing Over
Chromatids cross over in Meiosis I, swapping alleles
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Independent Segregation
Different combinations of chromosomes could arise from maternal and paternal chromosomes during Meiosis
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Genetic Bottlenecks
An event where a large proportion of the population dies reducing the number of different alleles in the gene pool, reducing diversity
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The Founder effect
When a new colony is started from a small number of organisms, so only a small number of organisms have contributed their alleles to the gene pool
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Selective Breeding
Where organisms with desirable qualities reproduce together
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Partial Pressure of Oxygen
A measure of oxygen concentration
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Oxygen dissociation curve in environments with low ppO2
Curve shifts to the left, higher affinity for O2, Hb is more saturated at the same partial pressure
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Oxygen dissociation curve in organsims with a high respiratory rate
Curve shifts to right, lower affinity for O2, Hb unloads oxygen more readily to respiring tissues
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Condensation Reaction
Joining on monosaccharides with the removal of water to form a glycosidic bond
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Structure and Function of Starch - Energy Storage in Plants
Made from 2 polysaccharides of alpha-glucose, amylose and amylopectin. Starch can be broken down to release glucose if it needs energy. The long, unbranched chain of amylose makes it compact- good for storage. Branched amylopectin-broken down quick
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Structure and Function of Glycogen - Energy Storage in Animals
Polysaccharide of alpha-glucose. Similar to amylopectin except lots more branches so quick energy release. Compact molecule so good for storage
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Structure and Function of Cellulose - Forms Cell Walls
Formed from long, unbranched, straight chains of beta-glucose. Cellulose chains linked by H bonds for form strong fibres- good structural support
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What are the stages of the cell cycle?
Mitosis -> G1: Organelle and Protein Synthesis -> S: DNA replication -> G2: Cell growth and more proteins made -> Mitosis
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Mitosis
Produces two genetically identical (clones) cells
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What happens in Interphase?
DNA unravels and replicates. Organelles replicate. ATP content increased
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What happens in Prophase?
Chromosomes condense. Centrioles move to opposite end of cell. Spindle fibres begin to form. Nuclear envelope breaks down
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What happens in Metaphase?
Chromosomes line up along the middle of the cell and attach to spindle fibres by their centromere
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What happens in Anaphase?
Spindle fibres contract separating chromatids and pulling them towards opposite end of the cell
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What happens in Telophase?
Chromatids reach opposite poles, uncoil and become long and thin again. Nuclear envelope reforms. Cytoplasm divides by Cytokinesis forming two genetically identical cells
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What is cancer and how can it be identified?
Cancer is the result of uncontrolled cell division caused by a mutation in a gene that controls cell division. It can be identified by rapid division of cells.
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What are Tissues?
A group of cells that share a common origin
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What is an Organ?
A group of different tissues that work together to perform a function
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What is an organ system?
A group of organs working together to carry out a function
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Why don't single celled organisms need a transport system?
A small diffusion distance means substances can diffuse directly in or out
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Why do multicellular organisms need Mass Transport Systems?
Diffusion would be too slow because some cells are deep within the body. Because of small SA:V ratio it would be difficult to exchange enough substances
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How are Fish adapted for Gas Exchange?
Gill filaments and lamellae give a big surface area for diffusion. Lamellae contain lots of blood capillaries with thin walls. Counter-current flow maintains large O2 concentration gradient across entire length of gill
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How are Insects adapted for Gas Exchange?
Air enters through pores called spiracles and travel along pipes called tracheae. 02 and C02 diffuse in/out along the concentration gradient. Tracheae branch off into tracheoles which have thin, permeable walls. Rhythmic abdominal movements move air
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How do insects control water loss?
Close spiracles using muscles. Waterproof waxy cuticle prevents water evaporating. Tiny hair trap moist air
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How do Xerophytes control water loss?
Sunken stomata trap moist air reducing evaporation. Curled leaves protect moist air from blowing away. Reduced number of stomata. Waxy cuticle stops evaporation. 'Hairs' trap moist air reducing conc grad
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What are the properties of Arteries?
Thick muscle wall can contract to control blood flow (also in arterioles). Elastic tissue can withstand high pressure. Endothelium is folded so can expand
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What are the properties of Veins?
Wide lumen with very little elastic/muscle tissue. Valves stop back flow.
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How is tissue fluid formed?
Pressure forces fluid out of capillaries and into spaces around the cells. Pressure reduces along the capillary so some water re-enters by osmosis. The rest of the tissue fluid is carried away by Lymphatic System
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What are the Apoplast and Symplast Pathways?
Apoplast goes through the cell walls (until the Casparian *****) whereas Symplast goes through the cytoplasms
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How do Cohesion and Tension move water up a plant?
Water evaporates from leaves -> this creates tension which pulls more water into leaf due to a lower Ψ -> water molecules are cohesive so whole column of water moves up
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How does Root Pressure move water up a plant?
When water is transported from the roots to the xylem this creates a pressure and shoves water already in the xylem further up
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What is Transpiration?
The evaporation of water from a plant's surface
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What factors affect transpiration rate?
Light (stomata open), Temperature (more water evaporates), Humidity (lower humidity, higher H20 conc grad), Wind (blows away moist air)
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How can members of the same species be identified?
Only members of the same species will be able to produce fertile offspring
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What is a Hierarchy?
A large group split into smaller sub-groups with no overlap
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How can DNA of two organisms be compared?
DNA Sequencing - looking directly at the base sequence. DNA Hybridisation - making a hybrid strand where one strand belongs to each organism, and seeing at what temperature the strand breaks. Higher temp - more Hydrogen bonds - more similar DNA
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How can two Proteins be compared?
Comparing Amino Acid sequence - similar organisms - similar proteins - similar Aa sequence. Immunological comparison - similar proteins will bind to same antibodies
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How can Courtship behaviour be used to classify a species?
Only members of the same species will do and respond to a particular courtship behaviour to prevent interbreeding and makes reproduction more successful
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How can antibiotics cause Osmotic Lysis?
Antibiotics inhibit enzymes that form chemical bonds in cell wall - weakens cell wall - water moves in by osmosis - cannot withstand pressure and bursts
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How can a Bacterium become resistant to Antibiotics?
Random mutations in the DNA of a gene - diff protein - diff shape - could mean the bacteria is no longer affected by a particular antibiotic
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How can Resistance be passed on?
Vertical Transmission - because bacteria reproduce asexually its daughter cells will have identical genes, including the resistance genes. Horizontal Transmission: Conjugation could happen meaning a copy of the plasmid is directly transferred
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Why is Biodiversity important?
Prevents extinction. More niches for different organisms. More sources of food. Crops and animals are not susceptible to disease
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Why does deforestation cause a decrease in Biodiversity?
Fewer plant species, fewer habitats, fewer niches, fewer food sources, less protection from predators.
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What values need to be known to calculate Index of Diversity?
Total number of organisms of all species. Total number of one species
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Other cards in this set

Card 2

Front

Intraspecific variation

Back

Variation with a species

Card 3

Front

Alleles

Back

Preview of the front of card 3

Card 4

Front

Phenotype

Back

Preview of the front of card 4

Card 5

Front

Genetic variation factors

Back

Preview of the front of card 5
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