BIOLOGY

USE THIS ONE NOT THE OTHERS THEY ARE FALSE PROPHETS!!!!!

Palisade Mesophyll

Palisade Mesophyll

Site of photosynthesis

Spongey Mesophyll

Site of photosynthesis and gas exchange. Contains air spaces

Air Spaces

Improve gas exchange in the plant as they are moist environments which improves diffusion of water out of the cell as well as increasing ability for gas absorption.

Guard Cells

Open and close stomata

Phloem

Transports water and assimilates up and down the cell - living

Cambium

Contains meristem cells

Xylem

Transports water up the plant by capillery action and cohession - dead. Strenghtened by lignin

Sieve tube element

long living tube in the phloem, has plasmodesmata connecting to a companion cell.

Sieve tube plate

Plates with many pores at the end of each sieve tube. Can be filled with callose in the event of infection to prevent the pathogen travelling through the plant

Companion cell

Attached to a sieve tube element to support the cell and cause translocation.

Translocation

Process by which companion cells cause water to move up and down phloem. H+ ions are actively transported out of the cell via proton pumps creating a higher concentration outside the cell. The protons follow their diffusion gradient and bind to a sucrose/H+ cotransporter protein causing H+ to moving into the cell and sucrose to be transported in against its concentration gradient. Sucrose then diffuses across the plasmodesmata into the sieve tube element, decreasing the cell's water potential. Water enters the cell via osmosis causing flow.

Grana

Stacks of thylakoids

Stroma

Fluid within chloroplasts but outside thylakoids. Site of the light independent stage

Thylakoid

Disk-shaped sac which contains photosystems. Site of the light dependent stage

Primary pigments

Chlorophyll a: found at the centre of photosystems Chlorophyll b: absorbs wavelengths 400-500nm

Photosystem II

Contains Chlorophyll a P680

Photosystem I

Contains chlorophyll a P700

Accessory pigments

absorb light specta != 680,700. e.g. Xanthophylls, carotene, phaephytin

What are the four stages of the light dependent stage of photosynthesis

Light harvesting by photosystems Photolysis Photophosphorylation Formation of reduced NADP

Why does photolysis happen and what is the reaction?

2H2O->4H+ + 4e- + O2 Hydrogen ions are used in photophosphorylation. Electrons enter the electron transport chain

Non-cyclic photophosphorylation

PSI and PSII, produces ATP and NADPH. Photons excite electrons in PSII, electrons escape chlorophyll and enter the electron transport chain - these electrons are replaced into chlorophyll by photolysis. Electrons passed along electron transport chain, this releases energy which is used to pump protons into the thylakoid space. Electrons enter PSI, ferredoxin then accepts these electrons and passes them to NADP in the stroma. Protons diffuse out of the thylakoid space, through ATPsynthase causing ATP to be made. H+ combines with electrons and NADP to from NADPH.

Cyclic photophosphorylation

Only involves PSI, produces less ATP than non-cyclic. Photons excite electrons in PSI, they leave the chlorophyll molecule and enter an electron carrier system and return to PSI. During the passage, a small amount of ATP is generated.

The Calvin Cycle

CO2 combines with RuBP catalysed by RuBisCO forming an unstable 6C intermediate. 6C intermediate breaks down into GP (glycerate-3-phospate) GP is reduced by NAPDH to form triose phosphate. 2 ATP is used. 2 TP then combine using ATP to reform RuBP. Here a carbon is lost - the cycle happens in 6s, 6RuBP->12GP->12TP, 2 TP leave the cycle to become other useful products while the remaining ten reform 6RuBP.

Uses of triose phosphate

Amino acids, glycerol, fatty acids, glucose (therefore, starch, sucrose and cellulose)

Type 1 diabetes

Patients are unable to produce insulin. A likely cause is an autoimmune disease which attacks β cells. The condition begins in childhood and symptoms develop very quickly.

Type 2 diabetes

The patient cannot effectively use insulin. This may happen if the patients β cells do not produce enough insulin or cells are not correctly responding to insulin. This is typically due to extreme overeating of carbohydrates and obesity. Often only diagnosed after complications have been seen.

Treatments for type 1 diabetes

Regular injections of insulin and regular monitoring of blood glucose levels.

Treatments for type 2 diabetes

Diet and exercise are the main treatments however in some cases drugs which stimulate insulin production, slow down the rate at which the body absorbs glucose from the intestine and even insulin injections may be used.

New Treatment for Type 1 Diabetes

Stem cell transplants. Stem cells taken from embryos are the current most promising type, taken from left over embryos for IVF. This circumvents the need for a donor pancreas, reduced rejection issues, and the patient would no longer need to inject insulin.

Gluconeogenesis

Glucose is synthesised from amino acids and lipids. Happens as a result of glucagon release when blood glucose lowers.

Glycogenolysis

Glycogen is broken down to form glucose. Happens as a result of glucagon release.

Glycogenesis

Conversion of glucose to glycogen as a result of insulin release.

α-cells

In the islets of Langerhans in the pancreas. Secrete glucagon when blood glucose is below the set point.

β-cells

In the islets of Langerhans. Secrete insulin when blood glucose is above the set point.

Totipotent stem cells

Able to differentiate into all cell types.

Pluripotent stem cells

Able to differentiate to form most cell types.

Multipotent stem cells

Able to differentiate to form some cell types.

Conservation

Preservation and management of the environment and natural resources. Maintaining species and genetic diversity.

In situ conservation

Within the natural habitat. Allows organism to adapt to changing conditions as well as preserving interspecies relationships. Generally cheaper than ex situ conservation.

Examples of in situ conservation

Wildlife reserves and marine conseration zones

Wildlife reserves management techniques

Controlled grazing - allow flora to regrow. Restricted human access - prevents trampling plants, avoid disturbing animals while they mate. Controlling poaching - defences to prevent access, issuing fines, removal of things like rhino horns. Feeding animals - ensure they reach mating age. Reintroduction of species. Culling of invasive species. Halting succession - in the UK habitats tend towards woodland, grazing species prevent growth of trees and therefore stop marshes and heaths from becoming woodland.

Marine conserves

Important areas for repopulation of fish species, often large areas are required.

Ex situ conservation

removal of organisms from their natural habitat, normally used in addition to in situ measures. ensuring the survival of the species.

Botanic gardens

Preservation of plant species with active management. World wide conserve 10% of global flora. Wild types are typically not preserved - a major flaw.

Seed banks

Hold many types of seeds dried and frozen in case a species goes extinct. Svalbard houses ~800,000 species of seeds. Seeds of tropical rainforest trees are mostly unable to be stored this way :(

Captive breeding

Programs for endangered animals to produce offspring and be reintroduced into the wild. Provide animals with shelter, food and vetternary care. Suitible breeding parnters or semen samples may be imported from other zoos. Techniques such as artificial insemination, embryo transfer and long term cryogenic storage of embryos are often employed.

Problems of captive breeding

Disease - species may have lost resistance to pathogens which exist in the wild. Behaviour - some behaviours such as searching for food may not be taught to species bred in captivity. Genetic variation - captive species may become genetically different from wild populations and even speciate. Habitat - natural habitats must first be restored before the species can be safely reintroduced.

IUCN

International Union for Conservation of Nature. Assist in securing agreements between nations. Publish the red list once a year detailing endangered animals.

CITES

Convention on International Trade in Endangered Species. Regulates international trade of wild plant and animal speces, and their products. Currently protects 35000 species.

The Rio Convention

1992, 172 nations held the Earth summit, resulting in: The covention on biological diversity (CBD) - requires country to develop national strategies for sustainable development. The United Nations Framework Convention on Climate Change (UNFCCC) - Take steps to stabilise greenhouse gasses in the atmosphere The United Nations Convention to Combat Desertification (UNCCD) - prevent reduction of fertile lands and effects of droughts though programmes of internation cooperation.

Countryside Stewardship Scheme

1991-2014, offered payments to farmers and land managers to enhance and conserve the English landscape. Aimed to make conservation part of normal farming. Sustain beauty and diversity of the landscape. Improving, extending and creating wildlife habitats. Restoring neglected land and conserving archaeological and historic features. Improving opportunities for countryside enjoyment.

Phylogeny

Evolutionary relationships between organisms. Independent of taxonomy/classification.

Taxonomy

Study of classification - grouping animals according to established criteria. Modern techniques rely on phylogeny and genetics but previously phenotypes were used.

Taxonomic orders

Domain Kingdom Phylum Class Order Family Genus Species

Advantages of Phylogeny

Produces a continuous tree, organisms arent forcefully grouped. Shows history of evolutionary lineages, taxonomy may mislead one to believe different groups of the same rank are equal.

Trachycardia

Heartbeat is rapid, over 100bpm. Normal, however, may be caused by problems in electrical control.

Bradycardia

Heartbeat is slow, under 60bpm. Many people have this because they are fit - more effiecent contractions.

Ectopic heartbeat

Extra heartbeats that are out of the normal rhythm. Happen at least once per day in healty people. May be linked to severe conditions if frequent.

Artial fibrillation

Rapid contractions in the atria but "normal" contractions in the ventricles, clear R waves but no clear P,S,T,U waves. How viruses cause damage to the host

How protists cause damage to the host

Digest cell contents and use materials to reproduce, repturing cells. Malaria is an example of a proctist which does this.

How fungi cause damage to the host

Digest and destroy living cells.

Which classes of pathogens produce toxins

Bacteria and fungi.

Ring rot

Bacterial disease affecting potatoes, tomatoes and aubergines. Damages leaves tubers and fruit. Once a crop is infected the field cannot be used to grow potatoes for 2 years.

Tobacco Mosaic Virus

Infects tobacco plants and 150 other plant species. Damages leaves, flowers and fruit.

Potato blight

Caused by a “fungus-like” proctist. Hyphae penetrate host cells and digest them, destroying leaves, tubers and fruit.

Black sigatoka

Fungal infection which affects bananas. Hyphae penetrate and digest cells turning the leaves black.

Tuberculosis

Bacteria infection which destroys lung tissue and suppresses host immunity. Those suffering from HIV/AIDS are more likely to suffer from TB. It is curable and preventable.

Bacterial Meningitis

Bacterial infection of the meninges (caused by multiple different bacteriums) which may spread causing septicaemia. Affects the vary young and teenagers 15-19. Requires immediate medical attention. Treatable with antibiotics and some forms can be vaccinated against.

HIV/AIDS

(Human immunodeficiency virus/ acquired immunodeficiency syndrome) Virus targets T helper cells, gradually destroying the host’s immune system. HIV is a retrovirus and causes cancer in some patients. HIV is passes through bodily fluids. HIV hides itself in the host genome and mutates rapidly making a vaccine very hard to develop. However, it is possible to slow progression through use of antivirals.

Influenza

Viral infection of ciliated epithelial cells, killing them and making the airways open to secondary infection. Flu viruses mutate regularly and vaccines must continually be developed for at risk groups.

Malaria

Caused by the proctist Plasmodium and transmited by female mosquitoes (the vector). Plasmodium reproduces within the mosquito and is transmitted when the mosquito bits someone, to feed her eggs, the proctist enters the person. From here Plasmodium is capable of hiding within red blood cells to evade detection and go on to infect the liver and potentially the brain. The disease is recurring and cannot be vaccinated against. It has limited cures but the vector can be controlled.

Ring worm

Fungul disease which infects mammals. Causes grey-white, crusty, infections circular areas of skin. Not damaging but may be itchy.

Athlete’s foot

Fungal infection, a type of ringworm which digests the moist skin between toes. Antifungal creams are an effective treatment.

Direct contact transmission

Faecal-oral microorganisms transmitted on hands. Kissing or contact with bodily fluids i.e. STIs. Skin-skin contact such as ringworm and athletes foot.

Inoculation (transmission)

Breaking skin - microtears during sex transmitting HIV. Animal bites - rabies. Puncture wound/sharing needles - septicaemia.

Ingestion

Eating contaminated food and drink - dysentery!

Fomites

Inanimate objects which hold pathogens, such as cosmetics, bedding and socks.

Droplet infection

Minute droplets expelled when coughing or sneezing can be inhaled, infecting the recipient

Vectors

Transmit pathogen from host to new host. Vectors include: rat fleas, mosquitoes, dogs, foxes and bats.

Plant’s physical defences against pathogens

Synthesis and release of callose, deposited between cell walls and cell membranes of infected cells.

Lignification of callose barriers. Callose blocks sieve tube plates.

Callose deposited into plasmodesmata.

Plant’s chemical defences against pathogens

Insect repellants such as pine resin and citronella.

Natural insecticides.

Antibacterial compounds such as phenols.

Antifungal compounds such as saponins which disrupt fungal membranes.

Anti-oomycetes such as glucanases which break down glucans.

General toxins.

RQ formula

CO2 produced/O2 consumed

RQ value for carbs

1

RQ value for proteins

0.8-0.9

RQ value for lipids

0.7

Homologus chromosomes

Chromosomes of the same length

Continuous varitation

A characteristic which can take any value within a range. Controlled by multiple genes (polygenes). Affected by genes and the environment.

Discontinuous variation

A characteristic which can only appear as specific values/catagories. Controlled by one or two genes. Mostly genetic.

Co-dominance

Two different alleles are both dominant and produce a unified phenotype distinct from either alone.

Dihibrid cross offspring phenotype ratio

9:3:3:1

Autosomal linkage

Alleles are on the same chromosome and more likely to be inherited together. This dramatically affects the phenotype ratio of offspring.

Recombination frequency

Measure of crossing over during mitosis.

Recombination fq = nO recombinant offspring/total offspring

A recomb fq of of 50% indicates no linkage. Less indicates impairment of independent assortment and that the genes ares linked.

Epistasis

Gene interaction at different loci. A gene that affects expression of another is called epistatic and the gene it affects hypostatic.

Dominant epistasis

Dominant allele results in effect on other gene.

Recessive epistasis

Protein required for biochemical pathway not produced.

Hardy-Weinberg Principles

p+q=1

p^2+2pq+q^2=1

Factors affecting evolution

Mutation - necessary for existence of different alleles

Sexual selection - increase frequency of alleles which code for successful mating characteristics

Gene flow - movement of alleles between populations, immigration and emigration.

Genetic drift - happens in small populations, change in allele frequency due to mutation

Natural selection - increase in individuals with characteristics which improve chances of survival

Founder effect

Example of genetic drift. Small population after environmental change over represents rare alleles making them more common as population reexpands. Results in very low genetic diversity.

Stabilising selection

Those of the average are most likely to survive and the norm is selected for while extremes are selected against.

Directional selection

Change in the environment results in phenotypes of one extreme being selected for.