Module 4 Flashcards
Pathogen =
a microorganism that causes disease.
Bacteria
• Can rapidly multiply in the right conditions • Cause disease by damaging cells or producing toxins that are harmful • Eg tuberculosis, bacterial meningitis, ring rot (plants)
Viruses
• Invade cells and take over the protein-synthesising organelles • Infect the cells with new DNA • Host cells eventually burst and release new copies of the viral DNA • Eg HIV/AIDS, influenza, tobacco mosaic virus (plants)
Fungi
• In animals, cause redness and irritation • This is due to hyphae released from the fungus • Eg black sigatoka (bananas), ringworm (cattle), athlete’s foot
Protoctista
• Feed on cell contents as they grow • Eg malaria, potato blight
Tuberculosis • Cause
• Bacterial • Mycobacterium tuberculosis • Divides slowly (every 20 hours) • Can survive for 6 months outside body
HIV/AIDS • Cause
• Virus • Human immunodeficiency • Attacks and destroys immune cells weakens immune system • Open to range of opportunistic diseases • Secondary infection
Malaria • Cause
• Eukaryotic organism • Plasmodium falciparum
Tuberculosis • Transmission
• Sufferer cough, catapulting droplets of saliva into air • Saliva contain tuberculi bacilli • High speed • Reach over 1-2m • 1 sneeze can have up to 40,000 droplets
Tuberculosis • Global Impact
worldwide • 1% of world newly infected each year • 8.8 million cases • 34% new cases occur in S.E. Asia • 1.6 million deaths
HIV/AIDS Transmission
• Exchange of bodily fluids • Sharing of hypodermic needles • Across placenta during child birth • From mother to baby during breast feeding • Use of unsterilized surgical equipment
HIV/AIDS Global Impact
• Worldwide • 45 million sufferers • 5 million new infections annually • 30 million have died • Rapidly rising in China
Malaria • Transmission
• Spreads by vector • Malarial parasites live in red blood • Feed on hemoglobin • Mosquito will suck parasitical gametes into its stomach • Gametes fuse to form zygotes in mosquito stomach • Plasmodium develops and moves to salivary glands • Mosquito bites person, injecting saliva • Plasmodium enters person • Migrates to liver • Multiplies and passes into blood • Cycle repeats
Malaria • Global Impact
• Kills 3 million annually • 300 million affected worldwide • limited to regions where anopheles mosquito can live
The most common means of transmission can be identified as five groups
Droplet transmission Physical contact • Faecal-oral transmission Transmission by spores Vector transmission
Droplet transmission
○ E.g. through sneezing - pathogen is contained within mucus ○ Type of direct transmission
Physical contact •
○ Common for skin diseases like ringworm, a fungal disease in cattle, which is spread by an infected animal brushing against an uninfected animal Direct transmission
Faecal-oral transmission
○ E.g. E. coli ○ Transmitted by consumption of food or water with traces of faeces from infected animal ○ Direct transmission
Transmission by spores
○ Spores are a resistant form of the pathogen ○ They can resist extremes of temperature, pH, and even strong disinfectants ○ E.g. anthrax ○ Direct transmission
Vector transmission
○ E.g. malaria ○ The pathogen is carried from one host to another via a vector ○ With malaria the vector is female mosquitoes ○ The pathogen cannot be spread directly from one host to another ○ Indirect transmission
how climate can also contribute to the spread of disease.
• Some vectors only live in hot climates, e.g. mosquitos carrying malaria • Many viruses, protoctists and bacteria survive better in warm climates • Very cold climates can kill pathogens
how Environment can also contribute to the spread of disease.
• Cramped and crowded environments are conducive to spread of disease ○ Droplet infection rate likely to be higher ○ Contact infection also much higher • Dirty environments harbour pathogens ○ E.g. using human sewage to fertilise crops is sometimes done in parts of the world ○ This is likely to cause the spread of faecal-oral pathogen spread
plant Physical barriers
• Passive • Cellulose cell wall • Lignin thickening of cell walls • Waxy cuticles • Bark • Closed stomata • Callose ○ Large polysaccharide deposited in sieve plates in phloem ○ Block movement of pathogens up and down plants to avoid infection of the entire plant • Tylose ○ Balloon-like swelling in xylem ○ Blocks xylem and stops pathogens from travelling this way around the plant
Production of chemicals passive
Terpenoids • Phenols • Alkaloids • Hydrolytic enzymes
Production of chemicals Active defences
Leaves sense presence of pathogens • Begin to prioritise use of energy in secreting harmful chemicals • Cellulose produced to further fortify the cell walls • Oxidative bursts: produce harmful oxygen molecules to target the pathogen
Primary defences
are those that prevent pathogens from entering the body
Secondary defences
are those that prevent pathogens from harming the body once it has infected the host.
Non-specific defences
are those which occur in the same way, no matter the pathogen, and don’t require identification of the antigen.
Specific defences
are immune responses carried out by the host which specifically target the pathogen.
Primary, nonspecific defences against pathogens in animals
Skin Inflammation Mucous Membranes Blood Clotting & Skin Repair Coughing and Sneezing
Skin
• Epidermis ○ Tough outer layer ○ Secretes sebum to waterproof skin ○ Keratin secreted, toughening skin ○ 20-30 cells thick • Dermis ○ 20-40 x thicker than epidermis ○ Contains sensory receptors cells, capillaries and hair follicles • Lower layers of the skin are site of cell division • Replace cells lost from surface • Sebaceous glands secrete lactic acid and fatty acids ○ Forms acidic environment ○ Disrupts bacterial processes
Mucous Membranes •
Lining of organs involved in protection and absorption • Present at most interfaces between body and external environment • Secrete sticky mucus and lysosomes enzymes • Can be lined with cilia
Blood Clotting & Skin Repair
• Body prevents excess blood loss • Clot acts as temporary seal • Prevents infection and first step in skin reparation • Requires calcium ions and 12 cofactors ○ Clotting factors • These initiate and see through the clotting cascade • After the clot, a scab forms, and the epidermis heals more permanently
Inflammation
• Caused by damaged cells • Damaged cells release histamines ○ Cause capillaries to dilate ○ Increase tissue fluid ○ Increase flood supply ○ Increased phagocyte supply • Damaged cells release chemokines ○ Chemicals to which cells can show chemotaxis ○ Attracts phagocytes • Phagocytes invade the tissues ○ Carry out phagocytosis
Coughing and Sneezing
• Reflexes that expel pathogen trapped in mucous • Effectively removes pathogen from airway tract
cells involved in the mucus-cough reflex
Goblet cells in trachea secrete gel-like mucus • Mucus traps pathogens and irritants that are inhaled • Cilia cells lining respiratory tract waft mucus towards the back of the throat • Cough reflex expels mucus and clears the airway
Phagocytes are .
a type of white blood cell (WBC), whose role is to trap pathogens and kill them. Phagocytes contain phagosomes: membrane bound organelles, which act as receptors, binding antibodies to the already pound pathogens. They may be assisted by proteins called opsonins.
note
• Pathogens can be recognized as foreign by chemicals markers on outer membrane called antigens • These are specific to the organism • Proteins in the blood, called antibodies, attach to these foreign antigens
Neutrophils
○ Multilobed nucleus - enhances flexibility of cell ○ Manufactured in bone marrow ○ Short lived ○ Released in large numbers
Macrophage
○ Larger cells ○ Manufactured in bone marrow ○ Tend to settle in organs, particularly lymph nodes
Phagocyte mode of action
Phagocyte envelopes and engulfs the pathogen • The membrane folds inwards: phagocytosis • Pathogen is trapped inside in vacuole called the phagosome • Lysosome fuse with the phagosome forming phagolysosome • Release enzymes into it, called lysins. • Lysins digest the bacterium • Products of the digestion are entirely harmless • Nutrients can then be absorbed into the cytoplasm or exocytosed into extracellular fluid
specific immune response contains
B and T cells They are white blood cells which have specialised receptors on their cell surface membrane. Their overall role is to produce antigens which neutralise the pathogenic antigen.
B Cells (B lymphocytes) can be…
• Plasma cells ○ Circulate in blood ○ Produce and secrete antibodies into circulation • B memory cells ○ Remain in the body for many years after the initial infection ○ Serve to ‘remember’ the antigen
T Cells (T lymphocytes) can be…
• T helper cells ○ Release cytokines ○ Stimulate B cell maturation ○ Promote phagocytosis • T killer cells ○ Identify and kill infected host cells ○ Especially important during viral infections• T memory cells ○ Long-term immunity • T regulator cells ○ Recognise when the pathogen has been removed and is no longer a threat ○ Alerts the rest of the immune system that it no longer needs to be active ○ Immune response ends
Other elements of the Specific Immune Response:
InflammationPhagocytesAntigen Presentation Antigen Recognition Clonal SelectionClonal Expansion Cell signalling
Inflammation and Phagocyres
• Attracts phagocytes • Attracted by chemotaxis
Phagocytes
• Phagocytes engulf and destroy pathogens in phagocytosis
Antigen Presentation
• Macrophages engulf pathogens • Do not fully digest it • Separate antigens • Display antigens on their surface • Become antigen-presenting cell (APC) • This attract lymphocytes which can neutralize the antigens
Antigen Recognition
• Cytokines produced by antigens attract T-helper cell • Thousands of different T-helper cells, which fit to different antigens • Effectiveness of T-helper cells depends on the closeness of the bonds
Clonal Selection •
Bound T-helper cells produce cytokines • Attract B-lymphocytes • Best fitting lymphocyte binds to the macrophage • Occurs in lymph nodes
Clonal Expansion •
Cytokines produced by T-helper cells cause B-lymphocytes to divide • Multiple B-cells produced • Rapid clonal expansion can cause mutations ○ As a result, increasingly close matches may be found • B-cells released into the bloodstream • Some B-cells make memory cells and are stored in glands and retained for life • Remaining B-cells circulate in the blood plasma • May become plasma cells, producing antibodies • Antibodies are produced in the blood on a large scale
Cell signalling
• Cells need to communicate to work effectively • This is achieved through release of cytokines and cell surface receptors • Receptors must be complementary to the signaling molecule ○ T and B lymphocytes have receptors that are complementary to the foreign antigen ○ When the antigen is detected, the lymphocyte is stimulated ○ Specialist surface receptors detect chemicals signals
Structure of Antibodies
• 4 polypeptide chains held together by disulphide bridges • Constant regions, which remains the same • Variable region which changes • Hinge regions, which allow for flexibility
• Primary Infection
○ When an infecting agent is first detected, it takes a few days for antibodies to be produced ○ Once pathogens have been dealt with, number of antibodies in the blood drops rapidly
• Secondary Infection
○ Antibodies do not stay in the blood ○ If the same infection occurs, antibodies must be produced again ○ This time, antibody production is much more rapid ○ Concentration of antibodies rise sooner and reaches a higher concentration
The overall, main action of antibodies is neutralisation. describe hrw process
• Attach to antigen on pathogen • Blocks binding site, preventing pathogen from binding to host cells
Antibodies can be grouped into 3 categories hat are they
• Agglutinins Antitoxins • Opsonins
• Agglutinins ○
Large antibody can bind many pathogens together ○ Immobilises them ○ Prevents them from entering cells as they are now part of a much biggers structure ○ Aids phagocytosis
Antitoxins
○ Antibodies can also bind to toxins released by the pathogens, rendering them harmless
Opsonins
○ Antibodies can label the pathogens as foreign to phagocytes ○ Speeds up the process of phagocytes identifying antigens
Artificial Active •
• Immunity provided by antibodies made as result of injection • Person injected with weakened virus, activating the immune system
Natural
Active •
• Immunity provided by antibodies made in immune system as a result of infection • Person suffer from diseases only once, then is immune
Artificial Passive •
• Immunity provided by injection of antibodies made by another individual
Natural
Passive •
• Antibodies provided via the placenta or breast milk • Makes baby immune to diseases that the mother is immune to • Very useful in the 1st year, when baby’s immune system is developing
Autoimmune diseases
e diseases that evolve when a person or animal’s immune system attacks a part of the host body, in absence of pathogenic infection. During clonal selection, lymphocytes that are programmed to attack ‘self’ are normally destroyed before entering the bloodstream.
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Vaccination
provides a way of artificially stimulating primary immune response without the risk of illness • Exposes immune system to the antigen ○ Attenuated pathogen ○ Isolated antigen• Allows the body to produce adapted memory cells • Allows for demonstration of secondary response when next exposed to the virus
Herd immunity
Provide vaccination to all population at risk • Once enough people are immune, the infection will stop spreading • Often, only the people at greatest risk or exposure are vaccinated
Ring immunity
• Used when new cases of disease are reported • People in the immediate vicinity of new cases are vaccinated • Populations around infection are vaccinated, preventing the spread
Influenza virus
ts threat is a good example case study of a mutating disease, which can affect a large number of people each year who are not vaccinated. • Influenza is a killer disease • Caused by a virus • Occasionally, mutations lead to a new strain • This may cause an epidemic ○ 1918 epidemic killed 40 million ○ A large-scale outbreak is called a pandemic • In order to prevent pandemic, vaccination occurs • People at risk are immunized • Strain of flu that are vaccinated against change each year • Research is undertaken to decide which strains are most likely to spread
Possible Sources of Medicines
Traditional Medicines Wildlife Modern Research Natural Medicine Further Research Personalised Medicine
Traditional Medicines •
80% of global population rely on traditional medicines • Many modern drugs have their origins in traditional medicine
Wildlife •
Wildlife can be observed to view self-medicating of animals: ○ Bears rub citrus oils to prevent insect bites ○ Birds line nests with medicinal leaves to protect chicks from blood sucking mites
Modern Research
• Nature is often used as a starting point for research • Scientist are often able to identify and isolate the active ingredient
Natural Medicine
• Natural diversity of plants brings hope for discovery of new medicines • New technology has allowed scientists to chemically screen plants for potential uses as medicines • Highlights importance of maintaining biodiversity • E.g. the concept of probiotics - harmless bacteria which compete with harmful gut bacteria effectively treat symptoms
Further Research
• Receptors on viruses can be sequenced • Drugs can then be developed to block these receptors
Personalised Medicine •
DNA of plants can be sequenced, allowing candidates to be identified as potential vaccinations • In future, might be possible to sequence genomes of individuals, identify disease, and generate personalised medicine for that condition
Benefits to antibiotics
Prevent growth of bacteria • Therefore prevent disease caused by bacteria
Risks of antibiotics
• Over the years have been over-used and misused • Misuse gives mutant bacteria the chance to populate hosts even if they are being treated with antibiotics • Antibiotics now are less likely to give the desired result • E.g. MRSA ○ Methicillin-resistant staphylococcus aureus ○ Requires hospitalisation and carefully monitored administration of limited-availability antibiotics ○ Can be lethal
Species
• A group of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics • The members are able to interbreed freely to produce fertile offspring
Habitat
• Place where an organism lives • Specific locality with a specific set of conditions • Organisms are well adapted to their habitats
Biodiversity
• The variety of living species • The degree of nature’s variety • It allows for the permanent stability of an ecosystem • Involves an equilibrium between species
three types of biodiversity
Habitat Species Genetic
Habitat
• Range of habitats • Each may be occupied by different species • Diverse habitats may lead to diverse species • It is essential to conserve these
Species
• Difference between species • This could be within a habitat, or a community • Differences could be structural or physical • We can collect data about different species ○ This will inform species richness
Genetic •
Genetic variation exists within a species • Degree of allelic variation between the members of a species • It is good ○ Lack of variation results in a lack of ability to adapt ○ Natural selection depends on variation
In order to measure biodiversity:
• All species must be observed • Number of individuals must be counted Ideally this should be done for all organisms, however this may not always be practical. Instead, a habitat can be sampled.
Sampling is
when a small, random portion of a habitat is selected and studied carefully. You can then multiply up the numbers of individual species found to give an estimate for the entire habitat.
Sampling allows us to:
• Study any impacts on the environment (EIA) • EIA is used to estimate effects of a planned development on the environment
Number of Samples • Depends on
• Depends on the size of the habitat and time • Number of samples should be sufficient to give an accurate measure of the number of species in habitat and relative abundance • If two areas are being compared, the same number of samples should be taken at each
Random Samples
• Samples must be randomly chosen • This avoids bias/subjectivity • You must estimate the size of the habitat and decide where to take samples • This can be done by: ○ Taking samples at regular distances ○ Use random numbers to plot co-ordinates ○ Select co-ordinates from a map and use GPS to find the exact location • However, this process may exclude infrequent plants ○ You should visually survey the area ○ Record any odd plants ○ Write these down, but without abundance ○ This is qualitative data ○ It cannot be used for statistical analysis
Sampling Plants
A square-frame quadrat can be used to define sample area • Plant species are identified, then abundance is measured • This is done by: ○ ACFOR abundance scale ○ Estimate percentage cover ○ Key can be used to identify species within the quadrat
Sampling Animals
• Sampling may disturb the habitat • Animals may be frightened away - this would give an unrepresentative sample • Animals must be trapped or caught, then an estimate made • They can be caught by: ○ Swamp Netting ○ Collecting from trees ○ Pitfall Trap ○ Tullgren Funnel ○ Light Trap
Species Richness
• This is the number of species present in a habitat • The more species present, the richer the habitat • Observe and record the species present in a habitat • Samples should be taken • Visual surveys should be taken, to ensure that nothing is missed • However, this does not take into account the number of individuals of each species • Not sufficient data to measure diversity alone
Species Evenness
• Is the number of individuals of each species • Relative to population size • Relative abundance of each species • A habitat with even numbers of species is likely to be more diverse than one with a dominant species • A quantitative survey is carried out to asses this:
Survey Frequency of Plants
• Count number of each species present in sample area • With smaller plants is easier to calculate percentage cover
Density of Animals
• Careful observation can be made, counting individuals • Animals can be captured, marked then released • This will give an idea of the population size
Simpson’s Index of Biodiversity
• Diversity index is a better way of describing biodiversity • It takes into account both species richness and evenness • Gives an idea of the number of each species relative to population size • Small and large populations are treated differently • Simpson’s index measure the diversity of a habitat • The formula is …you know it.
Where n = the number of individuals of a certain species And N = the total number of individuals of all species
High Index of Biodiversity means…
• Indicates a diverse habitat • Many different species live there • Small change to environment may only affect one species • If this species is only small population, then only a small proportion of the habitat is effected • Total effect on the habitat would be small • Tends to be stable habitat
Low Index of Biodiversity means…
• Suggests it is dominated by few species • Small change to the environment may affect one of the major species • Could damage or destroy the whole species • Small change would have a very large impact on the environment • Much less stable environment
Genetic diversity
refers to the number of different variations of alleles at a particular locus there is in a species or population. For example, rare and endangered species have a limited genetic diversity because there are only a few of them: their gene pool is small
Calculating genetic diversity
• Calculate % of loci in the population with more than one allele …. polymorphic gene loci/total number of loci times 1000
Many human activities contribute to loss of biodiversity
• Hunting for food • Over harvesting • Killing for protections • Killing to remove competitors for our food • Pollution • Habitat destruction • Inadvertent introduction of new predators to flora and fauna • Population growth
Consequences of climate change
• Migrations • Agriculture • Diseases Population growth
• Migrations
○ Loss of genetic variation means species will be unable to evolve ○ Reduction in the gene pool ○ Decreases genetic variation, limiting ability to evolve ○ Unable to adapt to changing environment ○ Environment is increasingly changing as a result of climate change ○ Only alternative for them is to move ○ This may result in the slow migration of entire ecosystems to the poles ○ Animals living in protected areas may be forced to move out, into unsafe environments just to survive
Agriculture ○
There will be many effects on plants ○ These include: – Higher carbon dioxide levels – Higher temperature, increasing growth rates – Longer growing seasons – Greater evaporation and precipitation – Change in distribution of precipitation – Loss of land due to sea level rise ○ Domesticated plants have little variation and so are at greatest risk ○ Unable to evolve and adapt ○ Farmers may find yields decreasing – They will be forced to change their crops – Climate may change greatly
Diseases
○ Crops grown in new areas will encounter new pests ○ They may not be resistant to these pests Pest population may increase due to longer growing periods ○ Human diseases which thrive in moist tropics may migrate to poles as climate changes ○ May cause spread of diseases
Population growth
• Destroy habitats to support our own agricultural needs • Alter ecosystems to provide ourselves with settlement space and food ○ Reduces biodiversity by reducing suitable habitat • More people = more carbon dioxide emissions
Reasons to Maintain Biodiversity
Moral reasons
• Last living member of a species dies • Species ceases to exist • 784 recorded extinction since 1500 • Since the spread of humans, around 100,000 years ago, the rate of extinction has risen for other species • Extinction is primarily caused by human activity
Reasons to Maintain BiodiversityBenefits of having large biodiversity
• Extinction reduces biodiversity • Human clearing of land fro agriculture removes habitats • This increases chances fo extinction • Modern farming often plants only one type of crop (monoculture) • Makes harvesting easier • However, this has a very low diversity and reduces the variation of animals in this habitat • Selective breeding is also used in agriculture, leading to genetic erosion • Genetic erosion reduces genetic diversity • Prevents organisms from adapting to survive changes in their environment
Reasons to Maintain Biodiversity Economic and Ecological Reasons
• Nature can provide us with help in future developments • Incredibly high value natural ecosystems ○ Help us with technological problem ○ Regulate the atmosphere ○ Purify fresh water○ Recycle nutrients ○ Crop pollination ○ Growth of timber, food and fuel • Essential processes that we need to survive
Reasons to Maintain Biodiversity Aesthetic Reasons
• All organisms have the right to live • Loss of habitat may displace organisms • Humans feel joy from observing nature • Natural systems are very important for our physical, social and mental health
Reasons to Maintain Biodiversity Other reasons
Allowing genetic diversity to decline means we may lose some natural solution to our problems • Nature may hold the answers to some of our problems ○ Already adapted species may be carefully bred to produce a transgenic species ○ May be able to survive new conditions created by climate change • Nature is a source of potential new medicines ○ Range of potential vaccines is entirely unknown ○ Huge medicinal potential that needs to be maintained
In situ methods involve
supporting natural ecosystems in the wild.Attempting to minimise human impact on environment • Protecting the environment
Ex situ methods mean
moving endangered species into man-made Conservation of endangered species outside of their natural environment • All of these techniques carry the risk of disturbance to the natural environment
environments for a more controlled approach.
In situ Legislation • Process Pros Cons
- Prevents hunting and land clearing
- Prevents any development • Prevents human activities
- My only be specific to an areas • Hard to enforce in smaller countries
In situ • Conservation Parks
Process Pros Cons
- Parks and reserves established • Permanently protects biodiversity • May even allow ecological integrity to be restored
- Permanent protection • Conflict may arise if animals escape
In situ Repopulation • Process Pros Cons
- Rebuilding of lost biodiversity • Habitats are reestablished in attempts to improve biodiversity
- Effective in rebuilding biodiversity
- Cost • Unknown impact on environment
• Zoos • Ex situ • Process Pros Cons
- Species held in captive • Endangered species may be bred to increase population size • Ultimate view of releasing into the wild
- Lowers likelihood of extinctions
- Animals are not kept in their natural habitat
• Seed Bank • Ex situ • Process Pros Cons
- Seed Bank • Collection of seed samples • Aim to collect all known species fo plants • Examples of rare and important species
- Seeds have almost infinite options for use in future
- Storage must be controlled • Seed viability and germination must be tested annually
International & Local Conservation Agreements Made to Protect Species & Habitats Loss of habitat and species is an international problem that affects the world as a whole. International cooperation is therefore essential and achieved through a number of agreements. what are the three
CITESConvention on BiodiversityEIA
CITES •
Convention of International Trade in Endangered Species • Agreed in 1973 • CITES aims to: ○ Regulate trade in selected species ○ Encourage trade does not endanger species ○ Permits enforced for trade of less endangered species ○ Allow trade for artificially propagated plants • International policies are hard to enforce • Demand almost always has a supply
Convention on Biodiversity
• Signed by 150 leaders in 1992 • Dedicated to promoting sustainable development • Our requirement for genetic and biological diversity • Aims are: ○ Conservation of genetic diversity ○ Sustainable use for nature ○ Shared access to genetic resources ○ Shared transfer of scientific knowledge and technology ○ Members must have both ex-situ and in-situ conservation programs ○ Encourages co-operation between members
EIA
• Under the Rio Convention, all members must undertake an environmental impact assessment before any developments • This aims to: ○ Avoid adverse impacts on environment ○ Ensure potential environmental impacts are taken into account ○ Promote international and national exchange of opinions and information ○ EIA are mainly carried out at local levels ○ It is a means of assessing the likely impact of a development ○ Ensures that local planning authority knows about any potential adverse impacts in the environment ○ Can help developers to develop their proposal and make it more environmentally friendly
Classification
• Process by which we allocate living things to groups • Arranged into groups of increasing similarity • This can be done artificially ○ For our convenience ○ E.g. — Flower guide by colour • Or Naturally ○ Basic unit of natural classification is species ○ Natural classification reflects evolutionary relationships ○ Closely related species can be grouped together ○ These groups can be grouped together ○ These groups are then arranged into a series of ranked and interconnected groups ○ Forms a hierarchy
Phylogeny
• The study of evolutionary relationships between organisms • Group of organisms arranged by how closely related they are • The closer they are related, the closer they are on the tree • Common ancestors are shared by groups ○ The closer the lines, the more recent the ancestor ○ All common ancestors are extinct • Species that belong to the same phylogenetic group are called monophyletic ○ Humans and gorillas are monophyletic
Taxonomy
• Study of the principles of classification • Study of differences between species • Species usually grouped according to physical similarities ○ Similar species are place together
Why do we classify things?
• To order them • For our convenience • To make studying them easier • To make identification easier • To help us to see relationships
Current Classification System
Species is basic unit of classification • As you rise through hierarchy, more variation is shown ○ Domain – All living things categorized in 1 of 3 – Bacteria, Archaea, Eukaryote ○ Kingdom – 5 Kingdoms ○ Phylum ○ Class ○ Order ○ Family ○ Genus ○ Species
Prokaryote Size • Mode of NutritionCell structureExample •
1-10 um •
• No nucleus • Loop of DNA • No membrane bound organelles • Small cells • Cells wall of peptidoglycan
Respiration • Carried out on mesosomes
Protoctista Size • Mode of NutritionCell structureExample •
• Eukaryotes • Single celled • Mostly single celled • Wide variety
400um • • Both autotrophic and heterotrophic • Some photosynthesize, some ingest prey
Fungi Size • Mode of NutritionCell structureExample •
- Eukaryotes • Mycelium consisting of hyphae • Walls made of chitin • Multinucleate cytoplasmSpores range from 2.1-3.3 um
- Saprophytic • Cause decay of organic matter • Gain nutrients from this
Planate Size • Mode of NutritionCell structureExample •
• Multicellular • Eukaryotes • Cells are surrounded by a cellulose cell wall
Autotrophic • Photosynthesize
Animalia Size • Mode of NutritionCell structureExample •
- Eukaryotes • Multicellular • Usually able to move around • Fertilized eggs develop into blastula
- 94um-30m
- Heterotrophic • Digest and absorb organic matter
Classifying a Species
•
• • At higher levels, differences are greatest • It is easiest to distinguish between these groups • As you move to lower groups, it becomes increasingly difficult to separate closely related species accurately • More and more detailed description is needed
•
Recent Systems
• Originally, single celled organisms with plant or animal characteristics were grouped with their respective groups ○ However, better microscopes made it clear this was not true ○ Something had to be changed • Fungi do not fit in ○ They move like plants ○ But do not photosynthesize ○ They digest nutrients like animals do • The resulting upheaval resulted in the 5 Kingdom classification
Using biochemistry in systems •
Biochemistry is increasingly used in classification • Determines the degree of relation • Differences reflect evolutionary relationships ○ Cytochrome C – Use in most organisms for respiration – Made from smaller sequences of amino acids – If the sequence is similar, two organisms are closely related – If it is different, they are not ○ DNA – DNA found in all living organisms – Always provides the genetic code – More similar the sequence the more closely related the species
vbinomial system
is a system which uses the genus and species name to name organisms, in order to improve clarity when referring to them. E.g., Homo sapiens
Darwin’s 4 Observations Four principal observations:
○ Offspring generally appear similar to their parents ○ No two individuals are identical ○ Organisms have the ability to produce large numbers of offspring ○ Populations in nature tend to remain fairly stable in size
• Darwin concluded that
○ There is a struggle to survive ○ Better adapted individuals survive and pass on their characteristics ○ Over time, number of changes gives rise to a new species
notes
• Realized that variation was key to understanding change • As all offspring are different, some are better adapted • These will survive and pass on their characteristics to the next generation • Less well adapted individuals will die before they reproduce • This means the population will not grow indefinitely • If variation occurs, over time this may lead to the formation of a new species • Darwin concluded that: ○ There is a struggle to survive ○ Better adapted individuals survive and pass on their characteristics ○ Over time, number of changes gives rise to a new species As well as Darwin’s research, modern day fossil, DNA and molecular evidence also holds to support the same theory.
• Brachiopods
○ Appear in rocks formed over 500 million years ago ○ Darwin found slight variation in these animals over time ○ Each era has its own characteristics ○ Allowed him to date the fossils
Armadillos
Armadillos are very similar to extinct glyptodont ○ Armadillos must have had a beneficial variation allowing it to survive ○ It is only 15cm long, much smaller than the glyptodont
Recent Fossil Finds
○ Fossils seem to grow in complexity over time ○ Evolution of the modern horse over 55 million years is very well recorded ○ However, there are many gaps in the fossil records ○ Fossils only form from bone and hard bits and under certain conditions ○ DNA – Genes can be compared by sequencing DNA – Shows how closely related species evolved recently as new species – Distantly related organisms have more differences in their DNA ○ Molecular Evidence – Certain molecules appear throughout the living world, suggesting one common ancestor – Closely related species will have evolved into 2 new species recently and have similar biological molecules – In species which evolved long ago, differences will be greater – Proteins, such as Cytochrome c provide evidence of this – Sequence of amino acids in Cytochrome. C can be compared between species – In species that are very different, changes are greater – They took different paths long ago and so their has been more time for changes
Molecular evidence
Molecular evidence for the theory of evolution could come up in a question linked with protein synthesis. • Mitochondria contain their own DNA called mitochondrial DNA (mDNA). This type of DNA is always inherited from the mother as it is acquired from the original ovum. This phenomenon aids us in tracing back lineages as their is no complicated crossovers or swapping involved in its passing between generations.
Variation is defined as the difference between individuals. It is the perseverance of variety. It can be continuous or discontinuous. Where does it occur?
• Interspecific variation can occur between individuals of different species • Intraspecific variation can occur between member of the same species • Variation can be used to distinguish different species and members within a species
Discontinuous Variation
• 2 or more distinct categories • No intermediate values • Members may be evenly distributed between different forms • There may be more of one type than another ○ Examples – Sex – Blood group • Nearly always caused by genes • Little or no environmental influence • Unusually very few alleles are involved
Continuous Variation •
2 extremes • Full range of intermediates • Most individuals are close to the mean value• Number of individuals at extremes is low○ Examples – Height – Length of leaves • May be caused by genes and environment acting together • It is caused by many genes, and often multiple alleles of each gene
Genetic Causes
• Variation is produced by: ○ Independent assortment of chromosomes ○ Crossing over, exchanging of alleles between homologous chromosomes • Variation is increased by fertilization during sexual reproduction • Origin of genetic variation are mutations
Environmental Causes
• Variation can be caused by environmental factors: ○ Sunbathing causes darkening of the skin ○ Lack of a balanced diet causes poor growth ○ Growing a plant in Mg deficient soil results in yellow leaves
sd
A low value indicates the data have a narrow range. A high value indicates a larger range. This suggests lower reliability of the data. The spread of the data = mean ± standard deviation
Adaptations of organisms to their environment
• All members of a species are different • They show variation from one another • Any variation that helps survival is an adaptation • Evolution works by selecting particular adaptation to survive from one generation to the next • These characteristics are passed on from generation to generation • After very many generations, are passed on to the next generation • This characteristic is known as an adaptation
Behavioral
• Aspect of behavior that helps an organism to survive • For example, earthworms rapidly withdraw when touched • They have no eyes and are unable to tell what is and is not a predator • This defense mechanism protects them
Physiological
• Ensures correct cell functioning • For example, the yeast Saccharomyces can respire sugars both aerobically and anaerobically depending on the amount of oxygen in the air • Producing the e correct enzymes to respire is an adaptation
Anatomical
• Structural adaptation • For example, many bacteria have flagella to help them move independently • The flagellum is a structural adaptation
notes
Natural selection is the ‘selection’ by the environment of particular individuals that show certain variations • They pass on their characteristics to the next generation • Individuals are selected by a ‘selection pressure’
How natural selection works
• A gene mutates to create a new allele • Members of the population are genetically diverse from one another • The mutated allele is beneficial to the organism, e.g. ○ Allows it to run faster and escape predators ○ Allows it to survive longer without water ○ Allows it to reach food in difficult access places • Members of the population/species with this mutation more likely to survive and reproduce • Mutated allele becomes more common as they are passed through generations (inheritance) • Over time, the population becomes better adapted to its ecosystem for survival
Selective Forces
• Availability of suitable food • Predators • Diseases • Physical and chemical factors
Speciation
• Formation of new species from existing one is called speciation • Long and slow process • Accumulation of changes • Means that individuals can no longer breed to produce viable offspring • Larger organisms tend to take longer ○ Bacteria can pass through several generations in a few hours ○ This is enough to allow speciation to occur
How does speciation happen?
• Reproductive barrier must be present • Organisms are unable to breed with others in their group • Beneficial variations are spread through reproduction ○ If changes occur, but only pass to half the group, only this half will benefit ○ A collection of small changes means that these members are different from others ○ They may become so different that they can no longer breed
Allopatric Reproductive Barriers
• Geographical separation • Physical separation prevents effective interbreeding
Sympatric Reproductive Barriers
• Reproductive barrier within the population • Physical, social or biochemical change • Prevents one member from breeding with another
Pesticide resistance in insects
• Mutations arise that enable affected individuals to survive pesticide treatment • These individuals live longer and reproduce • Their offspring also carry the mutation that allow them to survive the pesticide • Every generation, a greater proportion of the population are unaffected by the pesticide • The pesticide is now useless
not well adaptee organisms
○ These individuals died faster than their peers and did not have the chance to reproduce and pass on that gene
