HB2 Flashcards
What is biodiversity?
The number, variety and variability of living organisms on the planet.
What is extinction?
The loss of a species.
What is evolution?
The process by which new species are formed from pre-existing one over very long periods of time.
What is adaptive radiation?
The emergence of several new species from a common ancestor introduced into an environment.
- Species colonises an area with several riches.
- Ancestor evolves into several new species each of which is adapted to feed on a different resource
How does biodiversity vary?
Biodiversity is lowest around the poles (not many species) and is highest around the tropics. (at the equator it isn’t very diverse)
What is a species?
A group of organisms that can interbreed to produce offspring.
What are the reasons for endangered species?
- Loss of habitat
- Overhunting from humans
- Competition from introduced species
- Deforestation
- Pollution
- Drainage of wastelands
What is a mass extinction followed by?
A rapid diversification. (such as the asteroid hitting the earth - dinosaurs extinct)
Why should humans conserve?
- Humans depend on other species
- Food: wild species act as a gene pool, we could introduce these genes through cross breeding or genetic engineering to improve productivity.
- Aesthetic: we get pleasure from interacting with other species (pets, national parks etc.)
What is the process of natural selection?
- More offspring are produced that can be sustained.
- Competition for resources (food, habitat)
- Individuals with a beneficial variation in the population survive and reproduce
- Next generation therefore have been passed on these favourable characteristics and this then repeats.
- May lead to 2 different groups, significantly different enough to prevent breeding and therefore 2 different species.
What is classification?
Naming and organising of organisms into groups according to evolutionary relationships.
What is taxonomy?
Study of the principles behind classification.
Why do we classify?
- Make the study of organisms more manageable
- Support our ideas of evolution
- To allow scientists to communicate with each other.
How do we classify?
The modern classification system is called a phylogenetic hierarchy using a phylogenetic tree.
What is a hierarchy?
A large group of organisms split into smaller and smaller groups (downward)
What does phylogenetic mean?
The way the organisms are grouped in the hierarchy reflects how the group of organisms are related.
What is a taxon?
A group of organisms sharing basic features.
Each taxon is a level in the classification hierarchy.
What is the order of the classification hierarchy going from the largest to smallest groups and give an example of the human order.
- Kingdom (Anamalia)
- Phylum (Chordata)
- Class (Mammalia)
- Order (Primates)
- Family (Homindae)
- Genus (Homo)
- Species (sapiens)
How do taxonomists group organisms?
Similarities and differences.
Similar morphology or biochemical methods
How is similar morphology carried out?
Homologous structures - body parts that are structurally similar even if used for different functions (suggests shared ancestry and divergent evolution)
How are biological methods carried out?
Comparing certain molecules across different species to see how similar/dissimilar their structures are.
DNA comparison is often used.
Protein comparison is also used (similar amino acids in the cytochrome C)
How is the binomial system used?
Each species is given a name which uses the genus and the name of its species. The genus uses capitals whilst the species doesn’t. Allows a particular organism to have its own name but we can also see similarities between two species.
e.g. Homo erectus and Homo sapiens
Describe all 5 kingdoms.
Prokaryotae - Don’t have any internal cell membranes, ER, mitochondria, true nucleus or Golgi body. Has a cell wall made of murein. Bacteria and blue-green algae are examples.
Protoctista - eukaryotic organisms with membrane bound organelles and a true nucleus. Includes algae and slime moulds.
Fungi - body is made up of threads called hyphae which make a mycelium. Cell wall made of chitin. Feeding is heterotopic. Reproduce by spores that lack flagella. Includes yeast and mushrooms.
Plants - Feeding is phototrophic. Multicellular. Cell wall made of cellulose. Include flowers, mosses, ferns etc.
Animals - Heterotrophic feeding, no cell wall, show nervous coordination.
What does chordate mean?
Typically has a vertebral column/backbone (vertebrates) whilst non-chordate don’t (invertebrates).
Animal kingdom divided into these 2 categories.
What is the development of human evolution?
- Homo habilis: found 1.5-2.5 million years ago. Hunted using stone tools. Cranial volume was 750-800cm cubed.
- Homo erectus: found 0.5-0.6 million years ago. Used fire and lived in big groups. Cranial volume was 850cm cubed.
(- Homo neanderthalensis: diverse descendants of H. erectus that had larger brains than humans. Found 130,000 to 35,000 years ago. Stockier, with less prominent jaw, used wide range of tools and lived in shelter and hunted for wild animals. Lived in communities) - Homo sapiens: Found since 300,000 years ago. Hunter gatherers and bury their dead. Cranial volume is 1350cm cubed.
What the 2 main theories as to how H. sapiens evolved?
- Multiregional theory (directly evolved from different parts of the world.
2 Monogenesis/’Out of Africa’ (only African descendants of H. erectus gave rise to modern humans. Other regional descendants became extinct with out contributing to the gene pool. Humans spread from Africa less than 100,000 years ago.
Explain the reasons as to why the monogenesis/’Out of Africa’ explanation for human evolution is the favoured explanation.
Most famous fossils of H. sapiens were found in caves in France around 35000 years ago. Fully modern fossils of H. sapiens were found in Africa from around 100,000 years ago. Neanderthal fossils were also found near, suggesting that the two species coexisted.
The two species didn’t interbreed and couldn’t be ancestors of the area.
Neanderthal DNA was very different to the modern human (can’t be fully trusted however).
How do we work out common ancestry using genetic techniques?
- DNA: base pairs compared, more alike means the more close the organisms are.
- Amino Acids: The more similar the amino acid sequence the more closely related the species.
- Protein: responding to different antigens on proteins (antibodies respond to corresponding antigens creating a precipitate) the greater the degree of precipitate the closer the evolutionary relationship.
What four main functions does the human gut do?
1: Ingestion: taking I of food into the body through the mouth
2: Digestion: breakdown of large food molecules into simple soluble molecules by enzymes. Mechanical digestion takes place with teeth, and then rhythmical contractions of the gut. Digestive enzymes secreted.
3: Absorption: Passage of digested food through the gut wall into the blood.
4: Egestion: elimination from the body of food that can’t be digested (eg. cellulose)
How is food propelled through the gut?
Peristalsis - circular muscle of gut contracts behind the bolus and relaxes after wave of contraction has passed
What is the structure of the human gut?
- Outer serosa: consists of a layer of tough connective tissue that protects the wall of the gut and reduces friction from other organs.
- (Outer) longitudinal muscle and (inner) circular muscle which cause muscular contractions to produce peristalsis.
- Sub-mucosa: connective tissue (cont. blood and lymph vessels) to take away absorbed food products. Nerves coordinate peristalsis.
- Mucosa: Secretes mucus which lubricates and protects mucosa. Either secretes digestive juices or absorbs digested food.
- Lumen: cavity of gut, where bolus is.
What are the glands in the gut?
- Glands outside of the gut which secrete through tubes or ducts into the lumen.
- Salivary glands (mouth)
- Liver (bile into duodenum)
- Pancreas (pancreatic juice into duodenum) - Glands in form of cells in sub-mucosa eg. secrete mucus in the duodenum.
- Glands in from of cells in mucosa eg.
- Gastric glands in stomach wall, secretes gastric juice into stomach
- Glands in base of villus inn SI, secretes enzymes into small intestine.
What happens during digestion?
Large molecules are broken down into smaller products by enzymes.
- Carbohydrates broken down by amylase from a starch into a disaccharide and then maltase breaks this down into monosaccharaides.
- Proteins are broken down by endopeptidase which break the peptide bonds within the molecule and exopeptidase break the peptide bonds at the end of these shorter polypeptides. Creates amino acids.
- Lipids are broken down by lipase into fatty acids and glycerol.
What occurs in the first step of digestion?
1: MOUTH - Mechanical digestion occurs and food is broken down by teeth. The food is mixed with saliva which is secreted by salivary glands. This lubricates the bolus, maintains a pH of slightly alkaline in mouth and this is the optimum pH for the salivary enzyme amylase which breaks starch into maltose.
Bolus is swallowed (lubricated by mucus in saliva) and travels down the oesophagus.
What occurs in the second step of digestion?
2: STOMACH - food enters the stomach and is kept there by contraction of 2 muscle rings (one at entrance and one at duodenum exit). Contractions mix up food with gastric juices. This has a pH of 2 which kills most bacteria and is optimum pH for the enzymes. Also contains peptidase which hydrolyses the proteins to polypeptides.
The stomach wall contains gastric glands with peptic cells, oxyntic cells and goblet cells.
What do peptic, oxyntic and goblet cells do?
- Peptic cells (chief) secrete pepsin as pepsinogen which prevents enzyme from damaging the stomach tissues. Remains inactive until it reaches lumen of stomach where it is activated by HCl and then pepsin breaks down proteins. Doesn’t damage stomach wall due to mucus.
- Oxyntic Cells secrete HCl which makes stomach acidic which kills bacteria and activates protein-digesting enzymes.
- Goblet Cells secrete mucus which forms a protective layer on stomach wall, preventing pepsin and HCl from breaking down the gastric mucosa. Helps movement.
What occurs in the third step of digestion?
3: DUODENUM - made up of two regions; the duodenum and the ileum. Relaxation at base of stomach lets food in little by little to the duodenum.
- Bile is produced in the liver and stored in the gall bladder and then passes into the duodenum via the bile duct. This emulsifies lipids so that they have a larger surface area. Also neutralises acidity in stomach.
- Pancreatic juice is secreted form exocrine glands in the pancreas and enter the duodenum via the pancreatic duct. Contains endopeptidase, amylase and lipase.
The walls of duodenum have Brunner’s Glands which secrete alkaline juice and mucus. The alkaline juice keeps the optimum pH for enzymes and the mucus lubricates.
Enzymes are secreted by cells at the bottom of crypts of Lieberkuhn:
- Maltase breaks down maltose into 2 glucoses
- Sucrase breaks down sucrose into glucose and fructose
- Endopeptidase and exopeptidase breaks down polypeptides into amino acids.
- Dipeptidase breaks down dipeptides into amino acids.
Disaccharides and dipeptides are digested intracellularly into simple amino acids and monosaccharaides.
What happens in the process of absorption?
The ileum is well adapted for digestion as it as very long and has folds called villi which increase surface area, and on these are microvilli, also called a brush border, which further increases surface area for absorption.
ATP energy required so epithelial cells in ileum contain a lot of mitochondria.
- Glucose and amino acids are absorbed across epithelium of villi via diffusion and active transport. They pass into capillary network that is in each villus. Glucose diffuses into blood down a concentration gradient.
- Fatty acids and glycerol are passed into lacteal of villi from the epithelium.. This is a blindly ending lymph capillary in centre of the villus. They are then transported to lymphatic system which opens into the blood at the thoracic duct.
What occurs in the large intestine?
Divided into caecum, colon an the rectum. Water and mineral salts are absorbed by the colon. By the time it reaches the rectum, indigestible food is in semi-solid state (residues of cellulose, bacteria and sloughed cells) and is ejected as faeces. Called defecation.
What is the fate of digested products after absorption?
- Glucose is absorbed by cells from blood for energy release in respiration.
- Amino acids are absorbed by protein synthesis, any not would be deaminated and converted to urea.
- Lipids are used for membranes and hormones, excess stored as fat.
Describe cancer of the digestive system?
Cancer can occur in various areas of digestive system such as stomach, liver, pancreas, bowel.
Symptoms depend of site and extent of growth as well as tissue of origin. May be bleeding, disruption of function of the organ, rapid weight loss or blood in faeces (bowel cancer).
Can be treated with chemotherapy, radiotherapy and surgical removal to remove tumours.
Risk of cancer can be reduced y eating a healthy, balanced diet that is high in fibre, fruit and vegetables and is low in meat and saturated fat. GO VEG.
Describe Coeliac Disease
Caused by a protein called gluten found in wheat, rye and barley. Upon exposure an enzyme modifies the protein and the immune system reacts with the bowel tissue causing an inflammatory reaction. Leads to flattening of villi and this interferes with digestion.
Symptoms can be mild with lethargy to severe such as acute illness and weight loss. Avoided when on a life-long gluten free diet.
Describe diverticulosis/diverticulitis
Diverticulosis is when a small pouch in the colon bulge outwards through weak spots. Symptoms include mild cramps, bloating and constipation.
Diverticulitis is when these pouches become infected or inflamed. Symptoms are more severe, such as abdominal pain, nausea, vomiting, chills, cramping and constipation. Can lead to blockage, tearing, bleeding etc.
Caused by low fibre diet and is treated with a diet high in fibre. Diverticulitis can e treated with a course of antibiotics.
Describe a peptic ulcer.
A peptic ulcer is the erosion of the lining of the stomach wall. There is an increase in production of aid OR mucus lining is damaged.
Two major causes are bacteria H. pylori or long term use of medicines such as anti-flam drugs or aspirin.
Common symptoms are stomach pains made worse by eating, weight loss, nausea and vomiting.
Treatment involves a combination of: medicine to clear body of H. pylori, drugs to reduce stomach acid and drugs to protect stomach lining.
Why antigens may red blood cells carry?
A, B and Rhesus antigens.
What is agglutination?
Agglutination (otherwise known as clumping) occurs when an antibody and an antigen match (eg. A antigen with anti-A antibody). This creates a clump of antibodies.
Describe Anaemia.
Red blood cells made in the stem cells or bone marrow mature and the cell gets rid of the nucleus in order to make more room for haemoglobin. This the haem group.
In order to have this, iron minerals and vitamin B are required. If haemoglobin isn’t produced the body may be short of oxygen in tissues/organs.
Symptoms are: lethargy, shortness of breath, paleness and heart palpitations BUT they can progress to headaches, hair loss and ulcers.
People at high risk are menstruating women, pregnant of breastfeeding women, premature babies, vegetarians, people with cancer, athletes, people on fad diets and children going through puberty.
Common causes are: dietary deficiency (iron), failure of absorption, excessive bleeding (heavy periods, inner body injuries)
Can be diagnosed when a RBC count is significantly lower than 5.2mil cells in men or 4.8mil in women.
Treatment includes iron tablets, iron rich diet or a blood transfusion.
What is the 1st line of defence for immunity?
The physical barrier to the body to stop pathogens getting through.
- SKIN: the skin has a layer of healthy bacteria that fight any pathogens, as well as being tough to friction and many harms. If the skin is cut then a clot forms which dries to form a scab, preventing loss of blood and entry of pathogens. New cells grow underneath. (formed by fibrin fibres tangling to create a mesh.
- STOMACH: acid produced in stomach has a low enough pH to kill most bacteria that enters via food.
- MUCUS: any bacteria that enters the nose is caught in the mucus and is wafted down the oesophagus where it is swallowed into the stomach and killed or coughed out.
What is the 2nd line of defence for immunity?
The second line (Inflammation response/non-specific) is activated when the tissue is damaged (cut, graze, burn, scratch etc).
When the tissue is damaged the injury goes past the epidermis into the dermis. Pathogens enter the body.
Mast cells and basophils stimulate histamine release.
When histamine is released it dilates blood cells (increased blood flow), extra heat (slows down pathogen growth), capillaries more permeable for tissue fluid, blood capillaries more permeable to white blood cells, and attracts white blood cells to damaged tissue.
These white blood cells (neutrophils and macrophages) engulf pathogens through phagocytosis and once this has been completed eosinophil breaks down the histamine.
What are symptoms of histamine release?
- Pain
- Redness (increased blood flow)
- Itchy
- Swelling (dilated cells)
- Heat
What is the humoral immune response?
Immature B-Cells from the stem cells in the bone marrow divide via mitosis.
The B Cells mature and produce antibody receptors which embed in the cell membrane. There are many different B cells which respond to different antigens.
- Antigens in the cell membrane of the macrophage are recognised by B lymphocytes.
- B lymphocytes are triggered when specific binding sites on their surface membrane attach to antigens.
- Activated cells divide rapidly forming clones of plasma cells in lymph node. Most produce antibodies but some produce memory cells.
- These circulate and bind to the specific antigen and destroy it. Plasma cells are responsible for immediate defence against infection.
- Memory cells remember the antigen and are ready to go under immediate production to create antibodies.
What is the cell mediated response?
T Cells produced in the thymus gland mature since the child is being weaned. T lymphocytes leave the thymus when mature and circulate in blood and bodily fluids.
- macrophages engulf pathogens and present the antigens on their own membranes.
- binding sites on the surface of specific t lymphocytes recognise and fit the antigen
- t lymphocytes are triggered are multiply rapidly by mitosis.
- t killer cells destroy the antigen directly
- helper t cells activate B cells to initiate antibody response.
- t suppressor cells suppress other cells immune system
- memory cells remember the antigen and produce an even larger cone for rapid destruction of the antigen if it comes again.
What is an antigen?
a substance that triggers the formation of antibodies or reacts with them
can be non-self (foreign) or self-antigens
normally large complex molecules
What is an antibody?
glycoproteins that are in a group called immunoglobulins
made up of 2 heavy chains and 2 light chains. has an antigen binding site which is specific, so there is a variable at the top of each antibody. has a hinge region in the middle
What is natural active immunity?
exposed to infection and the body manufactures its own antibodies in response to the antigens on the infectious agent.
if the same agent is encountered again it can be eliminated before disease
What is natural passive immunity?
transfer of antibodies from mother to foetus across placenta. only temporary as there are no memory cells formed.
What is artificial active immunity?
vaccination. vaccine is injected into a healthy individual. antibody production is stimulated and memory cells are also formed so that immunity is gained to that disease
What is artificial passive immunity?
injection of ready made antibodies, no memory cells, only temporary.
useful against diseases that are difficult to immune such as tetanus.
What does a vaccination process look like?
Phase A (no curve) - primary latent period where the antigen is detected by B lymphocytes. divides rapidly to form a clone of plasma cells (most memory cells) Phase B (small curved peak) - primary response period where antibody conc increases before decreasing again Phase C (large curved peak) - secondary response if the antigen is reintroduced or persists. lower level of antigen triggers the response (shorter latent phase) larger clone.
How does HIV occur?
transmitted through blood/semen and enters through cuts in skin or needles contaminated. may have no other symptoms other than swollen lymph glands.
can remain latent for years before being activated. reduces helper T cells which means it reduces body’s ability to fight a disease.
symptoms include cancer (no killer T cells), weight loss, fever, diarrhoea and deteriorating brain function. pneumonia is often reason of death.
Stage 1: HIV positive with little/no symptoms
Stage 2: some symptoms, low helper T count (therefore killer T too)
Stage 3: clinical AIDS, symptoms appear
What is airborne transmission?
(droplet infection) mainly diseases of lungs and respiratory passages.
microorganisms are expelled in tin droplets of saliva/mucus through coughing, sneezing and breathing
whooping cough, TB, influenza and measles are spread this way.
