Unit 2 : Humans - Their origins and their adaptions

Structure of DNA
Polynucleotide-lots of nucleotides joined together. Each contains a pentose sugar=deoxyribose, a phosphate group and a nitrogenous base = A-T, G-C. Two polynucleotides join together by hydrogen bonding between bases.
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DNA is genetic material
DNA long and coiled up, so lots of genetic information can fit into a small space in the cells nucleus.
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Structure of RNA
Ribose sugar, Single polynucleotide strand, Uracil replaces Thymine, and always bonds to Astatine.
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Determining the sequence of amino acids in proteins
Different proteins have a different number + order of amino acids. This order of the nucleotide base in a gene determines order of amino acids in a protein. Coded by a sequence of 3 bases in a gene.
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RNA is a copied section of DNA
Single strand of gene's DNA used as template. RNA nucleotides in nucleus line up along template (G-C). Specific base pairing means RNA an exact reverse copy of DNA template.
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You can prove that DNA is genetic material
When viruses infect bacteria, they inject their genetic material into the cell. So the viral material is found inside the bacterial cell must be the genetic material.
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Sections of DNA that contain coded information that determines the nature and development of organisms.
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Alleles are genes that exist in different forms. They are positioned in the same relative position (locus) on homologous chromosomes.
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Proteins whose synthesis is controlled by DNA. They control metabolic pathways and thus influence the phenotype of an organism.
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How DNA's structure is related to it's function
Double helix=unwind so single strands ready for copy. Hydrogen bonds=break easily, so there are 2 strands with complimentary bases.
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How's RNA structure related to it's function
Small enough to leave the nucleus. Single stranded=bind to template of DNA
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Relationship between genes, proteins and enzymes
DNA sequence in a gene determines RNA sequence. RNA sequence determines amino acid sequence. Proteins + enzymes formed. Enzymes control metabolic pathway, which determines physical appearance.
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Semi-Conservative Replication experiment
2 samples of bacteria, 1 in light nitrogen, 1 in heavy nitrogen. As bacteria reproduce, they take up nitrogen. Sample of each is taken and spun in centrifuge. DNA from heavy settles lower down, it's taken out + put in light N.
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Semi-Conservative Replication experiment 1
It's left for 1 round of DNA replication, then another sample put in centrifuge. New DNA contains one strand of new light N, and one strand of old heavy N.
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Semi-Conservative Replication
H bonds broken, and DNA helix unzips. Bases match up using specific base pairing. DNA polymerase joins the nucleotides. H bonds form between strands.
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Role of DNA polymerase in DNA replication
Joins the nucleotides on the new strand together
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Relationship between DNA replication and the events of the cell cycle
DNA replicates to double its genetic content, so that when mitosis or meiosis occurs, each new cell, has a copy of the DNA.
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Increases cell number in growth and repair tissue. The cell divides to produce 2 new cells, each containing an exact copy of DNA from parent cell. All cells made in body contain same alleles as we grow from zygote-single fertilised cell. 'Asexual'
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Cells DNA unravels and replicates to double its genetic content. Organelles also replicate so it has spare ones, and its ATP content is increased to provide energy for cell division.
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Chromosomes condense. Bundles of protein 'centrioles' start moving to opposite ends of the cell, forming a network of protein fibres across the spindle. The nuclear envelope breaks down and chromosomes lie free in the cytoplasm.
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The chromosomes line up along the centre of the cell and become attached to the spindle by their centromere.
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Centromeres divide, separating each pair of sister chromatids. Spindles contract, pulling chromatids to opposite ends of the cell, centromere first.
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Chromatids reach opposite poles of spindle, and uncoil, 'chromosomes' again. Nuclear envelope forms round each group, so 2 nuclei. Cytoplasm divides, now 2 daughter cells 'genetically identical'. Each daughter cell starts interphase...
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Malignant tumours
Cancers. Grow rapidly, and invade+destroy surrounding tissues. Cells can break off the tumours and spread to other parts of the body.
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Benign tumours
Not cancerous. Grow slowly, often covered in fibrous tissue that stops cells invading other tissues. Often harmless, but can cause blockages + put pressure on organs, some end up malignant.
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Characteristics of tumour cells
Irregular shape, Nucleus larger+darker than normal + sometimes have 1+. Don't produce proteins needed to function. Different antigens on their surface. Don't respond to growth regulating processes. Divide by mitosis more frequently than normal.
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Cell division is controlled by genes
These genes contain instructions for making proteins that regulate cell growth + division.
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Chemical carcinogens and radiation may damage DNA
Chemicals-In cigarette smoke, Radiation-UV from the sun.
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What do tumour cells fail to respond to?
Normal growth regulating processes. They undergo metastasis and invade other organs.
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Cells break off the primary tumour. Cells enter the bloodstream. Cancer cells continue to divide in bloodstream. Cells invade other tissues or organs. Cells form secondary tumours.
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Role of tumour suppressor genes in preventing tumour growth
If a mutation occurs in a tumour suppressor gene, the protein that stop cells dividing/cause them to destruct, isn't produced and cells grow uncontrollably, resulting in a tumour.
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Skin Cancer
Environmental=Sunlight-contains UV radiation causing mutations. Sunbeds-emit UV. Genetic factors=some people have genetic predisposition to the disease.
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Lung Cancer
Environmental=Smoking-Carcinogens. Air pollution-exposure to exhaust fumes. Asbestos. Genetic=some people have a genetic predisposition.
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Colon cancer
Environment=Diet-high fat, low-fibre diet. Smoking-carcinogens. Genetic=genetic component.
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Ethical issues with treating smoking-related diseases
Self-inflicted so NHS shouldn't treat them. Unable to tell if disease deff smoking-related so unfair not to treat them.
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In humans, cells containing homologous chromosomes divide to produce gametes containing one chromosome from each homologous pair. No. of chromosomes is reduced from diploid number (2n) to haploid number (n).
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When gametes fuse in meiosis
When gametes fuse at fertilisation to form a zygote, the diploid no. is restored; enabling a constant chromosome no. to be miantained from generation-generation. Sometimes errors in meosis lead to inherited conditions. Non-disjunction leads to downs.
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Means of organising the variety of life based on relationships between organisms and is built around the concept of species.
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Taxonomic Hierarchy
Kingdom, Phylum, Class, Order, Family, Genus, Species
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Scientific name
First word-Genus, Second word-Species
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Group of similar organisms that are able to reproduce to give fertile offspring.
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Difference between original and recent classification
Originally, classification systems were based on observable features, but more recent approaches draw on a wider range of evidence to clarify phylogenetic relationships between organisms.
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Similarities in proteins and DNA.
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Similarities in structure and function of different body parts.
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Similarities in early stages of an organisms development.
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Similarities in the immune system
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Behavioural evidence
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Lamarck's theory
Individual organisms change over their lifetime to become better adapted to their environment, they lose characteristics they don't use, and develop ones that are useful. These changes are passed onto offspring.
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Darwin's theory
Individuals within a population show variation in their phenotypes. Individuals with better adaptations more likely to survive, reproduce and pass on good adaptations, these offspring make the no. with these adaptations increase.
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Natural selection
Individuals within a population may show a wide range of variation. Predation, disease + competition result in differential survival + reproduction. The organisms with a selective advantage more likely to survive, reproduce and pass on their alleles.
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Provides evidence for evolution. Fossil evidence can be dated by stratigraphy, potassium-argon dating and carbon dating.
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Happens when populations of the same species become reproductively isolated.
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4-2 million years ago. Long arms, short legs, brain roughly 35% the size of modern human brain.
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Homo Habilis
2.5-1.5 million years ago. Same size as Australopithecus but had a larger brain and less protruding jaw.
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Homo Erectus
2-0.3 million years ago. Taller, around 1.8m tall. Larger brain and even less protruding jaw than habilis.
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Homo Neanderthalensis
300,000-25,000 years ago. Similar height to Homo sapiens, robust bone structure and a larger brain.
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Homo Sapiens
200,000 - present. Flattest jaw and a large brain.
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Evidence of diet
Comes from teeth, bones and tools. Small canines and big molars if ate plants. Shaper canines and incisors for meat eaters.
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Different interpretations of limited evidence
1932-incomplete lower jaw found made ramapithecus appear human-like. 1975-more complete jaw found stated jaw was less human-like.
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Cultural evolution accompanied physical change
Development of early stone tools and the control of fire. Interpretation of archaeological evidence and possible uses of artefacts.
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Collect wild plants and hunt wild animals. Characteristics of this way of life show they were limited to do this by the size and structure of groups, range about a home base, division of labour and group cooperation.
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Humans adaptations
Increase the probability of: survival in their environment, successful reproduction and successful reproduction by their offspring.
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Anatomical adaptations
Structural features- Bipedalism=walking on two feet. Opposable thumbs=thumb can be pushed against fingers. Skin colour=skin pigment melanin absorbs UV so stop sunburn. Surface area-volume ratio in diff climates
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Physiological Adaptations
Increase in breathing rate=get more oxygen+lose more CO2. Increased heart rate=deliver oxygen to muscles faster. Changing the energy source used by muscles=provides enough energy for respiration if one energy source runs low.
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The medulla and stretch receptors control breathing rate
Inspiratory centre in medulla sends nerve impulses to intercostal and diaphragm=contract. and expiratory centre, inhibiting its action. Air enters lungs due to pressure diff between lungs. Lungs inflate, stretch receptors in lungs r stimulated...
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The medulla and stretch receptors control breathing rate 1
Sending nerve impulses, that inhibit inspiratory centre, back to medulla. E.C then sends nerve impulses to diaphragm and intercostal muscles to relax=lungs deflate, expelling air. Stretch receptors become inactive,I.C no longer inhibited + cycle rest
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Breathing rate increases due to increased muscular activity
During exercise, CO2^, pH decreases. Chemoreceptors in medulla, aortic bodies + carotid bodies detect decrease + send signal to medulla to send more nerve impulses to intercostal + diaphragm, ^rate+depth of breathing. Gaseous exhange speeds up.
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Medulla controls heart rate
Nerve impulses are sent from the cardiac centre to the SAN. These nerve impulses speed up/slow down our heart rate.
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Decreased blood pH causes an increase in heart rate
Decrease detected by chemoreceptors, which send nerve impulses to brain, which sends nerve impulses to SAN to increase heart rate.
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Increased blood pressure causes a decrease in heart rate
Pressure receptors in aorta wall in carotid sinuses detect changes in arterial b.p + inform brain. If pressure 2 ^, nerve impulses to C.C. send own to SAN to slow h.r down, if 2 low, tell it to speed up.
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Cardiac Output
Heart rate (bpm) x stroke volume (cm3)
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Changes in energy source used by muscles during exercise
Energy from breakdown of ATP immediate energy source, made from breakdown of glucose, glycogen + triglycerides energy for muscle contraction.
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Aerobic respiration
At rest. Uses O2 and produces CO2. Releases more energy from each glucose molecule than anaerobic respiration
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Anaerobic respiration
During exercise. Doesn't need O2. Produces lactate, which builds up in blood. It lowers blood pH, which causes pain known as muscle fatigue. Less efficient at releasing energy so doesn't make as much ATP.
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Oxygen debt
Amount of O2 needed to get rid of toxic Lactate produced during exercise. Some broken down in the muscles, some carried in the liver and changed to glucose and stored as glycogen.
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O2 carried round body in red blood cells by protein-H. O2 joins to H in lungs to form oxyhaemoglobin.
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People living at high altitudes
More red blood cells, so more haemoglobin to carry oxygen.
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Behavioural and sociological adaptations
Communication using facial expressions-helps everyone know what they're thinking. Development of language during childhood-allows young to communicate needs to parents. Extended childhood-children can learn more from parents.
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Adaptations of parasites inside host
Thick outer covering-protect from digestion, anti-enzymes-inhibit digestive enzymes. Antigenic variation-continually changes its surface antigens. Living inside host cell-antibodies of immune system can't reach them.
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Adaptations of parasites to increase infection of new host
Produce lots of offspring-more likely to survive and infect new host. Use secondary host for transmission-like mosquitoes.
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Faeces of infected animal contain parasite eggs. People contaminated if touch faeces or pet animal then put hands in mouth.
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Parasite have no locomotion organs, digestive system or nervous system
So don't need to move to look for food, use this energy for other things, don't need eyes and don't need to control movement.
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Evidence for early farming
Remains of settlements. farming tools, remians of seed stores, evidence of domesticated animals, and artwork.
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Landscape + ecosystems in the UK are the result of human activities
Deforestation to produce arable and grazing land. Wetlands drained for farming.
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New Forest
Mostly dense woodland. Then cleared for farming until soil quality became poor. Then woodland became replaced by arable and grazing fields. In 11th Century, area declared a royal hunting ground and so large areas preserved.
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Cultivation of crops and domestication of animals
Led to surplus food and the establishment of larger settlements.
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Selective breeding
Cereal=rice, wheat + barley-high germination rates, high yields, resistance to disease+frost. Dogs=size, appearance, temperament-hunting dog, pet, herding dog. Cattle=pull carts + ploughs, and provide meat, dairy and leather.
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Other cards in this set

Card 2


DNA long and coiled up, so lots of genetic information can fit into a small space in the cells nucleus.


DNA is genetic material

Card 3


Ribose sugar, Single polynucleotide strand, Uracil replaces Thymine, and always bonds to Astatine.


Preview of the back of card 3

Card 4


Different proteins have a different number + order of amino acids. This order of the nucleotide base in a gene determines order of amino acids in a protein. Coded by a sequence of 3 bases in a gene.


Preview of the back of card 4

Card 5


Single strand of gene's DNA used as template. RNA nucleotides in nucleus line up along template (G-C). Specific base pairing means RNA an exact reverse copy of DNA template.


Preview of the back of card 5
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