Emily O’BrienA4

Final Exam Extra Credit – IB Biology Objectives

TOPIC 4: GENETICS

4.1 Chromosomes, Genes, Alleles, & Mutations

4.1.1 State that eukaryote chromosomes are made of DNA and proteins.

4.1.2 Define gene, allele, and genome:

Gene—a heritable factor that controls a specific characteristicAllele—a form of a gene, differing from other alleles of the gene by a few

bases at most and occupying the same locus as the other alleles of that geneGenome—the whole of the genetic information of an organism

4.1.3 Define gene mutation:

Gene Mutation—a change to the base sequence of a gene

4.1.4 Explain the consequences of a base substitution mutation in relation to the processes of transcription and translation, using the example of sickle-cell

anemia.

The smallest mutation is called base substitution; a single incorrect base is substituted for the correct base. This can have devastating effects. For

example, sickle cell anemia is caused by a single base substitution mutation. An A is replaced for a T on the DNA strand in the sequence CTC. Now, instead of the

DNA sequence reading CTC—which would code for the codon GAG—the DNA sequence reads CAC—which codes for the codon GUG. Since the DNA code changed, the mRNA codon changed, and this new codon codes for a different amino acid. Instead of glutamic acid—which GAG codes for—valine—which GUG codes for—is added to the polypeptide chain. This causes red blood cells

to become sickle-shaped instead of round; this condition is known as sickle cell anemia and is the result of a single base substitution mutation.

4.2 Meiosis

4.2.1 State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei.

4.2.2 Define homologous chromosomes:

Homologous Chromosomes—have the same genes as each other, in the same sequence, but not necessarily the same alleles of those genes

4.2.3 Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells.

Emily O’BrienA4

1. Prophase I- homologous chromosomes pair up - spindle microtubules grow from each pole to equator- nuclear membrane breaks down

2. Metaphase I- chromosome pairs line up on equator

3. Anaphase I- homologous chromosomes are pulled to opposite poles (halves chromosome number)- each chromosome consists of two chromatids

4. Prophase II- cell divides into 2 haploid cells- new spindle microtubules grow

5. Anaphase II- centromeres divide making chromatids into separate chromosomes

6. Telophase II- both cells divide into 4 haploid cells (each nucleus has half as many chromosomes as parent)

4.2.4 Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).

A non-disjunction is when chromosomes do not separate and causes changes in chromosome number. For example, trisomy 21 (Down Syndrome) occurs when the 21st pair contains 3 chromosomes instead of 2.

4.2.5 State that, in karyotyping, chromosomes are arranged in pairs according to their size and structure.

4.2.6 State that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome

abnormalities.

4.2.7 Analyze a human karyotype to determine gender and whether non-disjunction has occurred.

4.3 Theoretical Genetics

4.3.1 Define genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier, and test cross.

Genotype—genetic make-up of an organismPhenotype—what an organism physically looks likeDominant Allele—an allele that masks anotherRecessive Allele—the masked alleleCodominant Alleles—alleles that are equally expressedLocus—a gene’s location on a chromosomeHomozygous—having 2 identical alleles of a gene

Emily O’BrienA4

Heterozygous—having 2 different alleles of a geneCarrier—an individual who carries the allele, but is phenotypically normalTest Cross—determines the unknown genotype of a dominant allele before conducting a monohybrid cross

4.3.2 Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnet grid.

4.3.4 Describe ABO blood groups as an example of codominance and multiple alleles.

There are four different blood types: A, B, AB, and O. Blood type AB is an example of codominance because both the A and B alleles are expressed. However, in blood type A, only the A alleles are expressed, and in blood type

B, only the B alleles are expressed. Blood type O is the recessive blood type.

4.3.5 Explain how the sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans.

Girls = XXBoys = XY

4.3.6 State that some genes are present on the X chromosome and absent from the shorter Y chromosome in humans.

4.3.7 Define sex linkage.

Sex linkage—an allele found on the sex chromosome (most on X—making boys more susceptible)

4.3.8 Describe the inheritance of color blindness and hemophilia as examples of sex linkage.

Color blindness and hemophilia are two examples of recessive, sex-linked conditions. The X chromosome can have a dominant allele of the condition or

the recessive allele. Therefore, boys are more likely to have a recessive, sex-linked condition because they only have one X chromosome. Meanwhile, girls have two X chromosomes and therefore, need two recessive alleles to have the condition.

4.3.9 State that a human female can be homozygous or heterozygous with respect to sex-liked genes.

4.3.10 Explain that female carriers are heterozygous for X-linked recessive alleles.

Females carriers are heterozygous for X-linked recessive alleles and therefore have a 50:50 chance of passing the recessive allele on to their son or daughter. However, since males have only one X chromosome, they therefore have a 50:50 chance of actually getting the condition from the

Emily O’BrienA4

recessive allele. Females, on the other hand, have a lesser chance of getting the condition because females have two X chromosomes.

4.3.11 Predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance.

Dragon Lab

4.3.12 Deduce the genotypes and phenotypes of individuals in pedigree charts.

4.4 Genetic Engineering & Biotechnology

4.4.1 Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA.

1. DNA sample is extracted (usually very small)2. Put DNA in special PCR tube designed for even heat distribution3. Add primers to the PCR tube in order for them to attach to sites at either end

of the DNA strand (very reliable)4. Add nucleotides to the PCR tube in order to create DNA copies5. Add DNA polymerase which causes the free nucleotides to bond to the parent

strand6. PCR tube is placed in a DNA Thermal Cycler7. 95° C – DNA strands separate8. 50° C – primers crowd the DNA strands so they don’t come back together9. 72° C – DNA polymerase locates primer and adds complementary base pairs

to the parent strands10. Steps 7-9 are repeated for many cycles

END RESULT = MANY COPIES OF A SPECIFIC DNA SEQUENCE

4.4.2 State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size.

4.4.3 State that gel electrophoresis of DNA is used in DNA profiling.

4.4.4 Describe the application of DNA profiling to determine paternity and also in forensic investigations.

DNA profiling can be used to determine paternity, which is determining a child’s parent. All the bands in a child’s gel electrophoresis must come from

the mother or father. It can also be used in forensic investigation, obtaining evidence for court cases. For example, a suspect’s gel can be compared to one obtained at the crime. If the bands match up, the suspect is guilty, but if they don’t match up, the suspect is innocent.

4.4.5 Analyze DNA profiles to draw conclusions about paternity or forensic investigations.

4.4.6 Outline three outcomes of the sequencing of the complete human genome.

Emily O’BrienA4

o We could study how genes affect human developmento We could identify genetic diseaseso We could create new drugs based on genetics

4.4.7 State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

4.4.8 Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast, or other cell), restriction enzymes (endonucleases), and DNA ligase.

1. Plasmid DNA is removed from bacteria cell (bacteria cell dies)2. Restriction enzymes—enzymes which cut double stranded DNA molecule at

specific recognition sits; creates blunt or sticky ends—are added to cut the DNA at a specific location

3. The gene of interest is cut out of human DNA with the same restriction enzyme

4. Human gene is inserted into plasmid using ligase creating recombinant DNA5. Plasmid is inserted into a new bacteria cell, which copies the gene as the

bacteria cell multiplies

4.4.9 State two examples of the current uses of genetically modified crops or animals.

1. Bt Corn- contains a bacteria which resists bugs

2. Purple Tomato- contains extra antioxidants

4.4.10 Discuss the potential benefits and possible harmful effects of one example of genetic modification.

1. Bt Corn- benefits = no insecticides, no bugs- cons = unknown health effects on humans

2. Purple Tomato- benefits = more antioxidants, less chance of heart disease/cancer- cons = unknown health effects

4.4.11 Define clone.

Clone—producing an identical copy of something (gene, tissue, organism, etc)

4.4.12 Outline a technique for cloning using differentiated animal cells.

1. A cell is taken from the organism to be cloned2. The nucleus is removed and the rest of the cell is thrown away

Emily O’BrienA4

3. An egg cell is taken and the nucleus replaced with the nucleus of the original organism

4. The cells divide to create an embryo5. This embryo can be used for therapeutic cloning (growing part of an

individual) or reproductive cloning (growing a whole individual)

4.4.13 Discuss the ethical issues of therapeutic cloning in humans.

o Would women be exploited for their eggs for human cloning?o Does a clone have a soul?o Should there be a global band on cloning?o Who decides who is cloned?

TOPIC 5: ECOLOGY AND EVOLUTON

5.1 Communities & Ecosystems

5.1.1 Define species, habitat, population, community, ecosystem, and ecology.

Species—a group of organisms with similar characteristics, which can interbreed and produce fertile offspring

Habitat—the environment in which a species normally lives or the location of a living organism

Population—a group of organisms of the same species, who live in the same area at the same time

Community—a group of populations living together and interacting with each other in an area

Ecosystem—a community and its abiotic environmentEcology—the study of relationships in ecosystems—both relationships

between organisms and between organisms and their environment

5.1.2 Distinguish between autotroph and heterotroph.

Autotroph—organisms that synthesize their own organic molecules (food) from simple inorganic substances; producers

Heterotroph—organisms that obtain organic molecules (food) from simple inorganic substances; consumers, detritivores, and saprotrophs

5.1.3 Distinguish between consumers, detritivores, and saprotrophs.

Consumers—organisms that ingest organic matter that is living or recently killed

Detritivores—organisms that ingest dead organic matterSaprotrophs—organisms that live on or in dead organic matter, secreting enzymes into it and absorbing the products of digestion

5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms).

Emily O’BrienA4

Food chain—sequences of trophic relationships, where each member in the sequence feeds on the previous one

Passionflower - Heliconius butterfly - Tegu lizard - Jaguar(Passiflora (Heliconius erato) (Tupinambis (Panthera onca)schummaniana) teguixin)

Carrot plant - Carrot fly - Flycatcher - Sparrowhawk - Goshawk(Daucus carota) (Psila roea) (Muscicapa (Accipiter (Accipiter

striata) nisus) gentilis)

Sea Lettuce - Marine iguana - Galapagos snake - Galapagos hawk(Ulva Lactuca) (Amblyrhyncus (Dromiscus biserialis) (Buteo

cristatus) galapagensis)

5.1.5 Describe what is meant by a food web.

A food web is a diagram that shows all the feeding relationships in a community. The arrows indicate the direction of energy flow. Complete food web diagrams are very complex.

5.1.6 Define trophic level.

Trophic level—an organism’s position in a food chain

5.1.7 Deduce the trophic level of organisms in a food chain and a food web.

5.1.8 Construct a food web containing up to 10 organisms, using appropriate information.

FOOD WEB ASSIGNMENT

5.1.9 State that light is the initial energy source for almost all communities.

5.1.10 Explain the energy flow in a food chain.

The arrows of a food chain show the flow of energy in a community. About 10% of the energy is lost between each trophic level in a food chain.

5.1.11 State that energy transformations are never 100% efficient.

5.1.12 Explain reasons for the shape of pyramids of energy.

About 10% of energy is lost between each trophic level, and therefore only 90% is passed on.

5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled.

Emily O’BrienA4

Energy cannot be recycled; it is supplied to ecosystems in the form of light, flows through food chains, and is lost as heat. Nutrients are not resupplied, so they must be reused. Carbon, nitrogen, phosphorus, etc. are absorbed from the environment, used by living things, and then returned to the environment (carbon cycle).

5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients.

5.2 The Greenhouse Effect

SKIP

Emily O’BrienA4

5.3 Populations

5.3.1 Outline how population size is affected by natality, immigration, mortality, and emigrations.

1. Exponential phaseThe population increases exponentially because the natality rate is higher than the mortality rate. The resources needed by the population such as food are abundant, and diseases and predators are rare.

2. Transitional phaseThe natality rate starts to fall and/or the mortality rate starts to rise. Natality is still higher than mortality so the population still rises, but less and less rapidly.

3. Plateau phaseNatality and mortality are equal so the population size is constant. Something has limited the population such as: shortage of resources, more predators, more disease or parasites. All of these factors limit population increase because they become more intense as the population rises and becomes more crowded. They either reduce the natality rate or increase the mortality rate. If the population is limited by a shortage of resources, it has reached the carrying capacity of the environment (the maximum population size that can be supported by the environment).

5.3.2 Draw and label a graph showing a sigmoid (S-shaped) population growth curve.

5.3.4 List three factors that set limits to population increase.

1. Shortage of resources (food, etc.)2. More predators3. More disease or parasites

5.4 Evolution

Emily O’BrienA4

5.4.1 Define evolution.

Evolution—the cumulative change in the heritable characteristics of a population

5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures.

Fossil Record- the existence of fossils is hard to explain without evolution- for example: Acanthostega is a 365 million year old fossil with a backbone,

four limbs, 8 fingers, and 7 toes- similarities and differences to vertebrates today (missing link)- land vertebrates could have evolved from fish via an aquatic animal with

legs

Selective Breeding in Domesticated Animals- domesticated animals are clearly related to wild species- by selecting individuals with desirable traits and breeding from them

different species can be developed- striking differences between domestic and wild species show that species

can evolve rapidly

Homologous Structures- there are remarkable similarities between structures of organisms

(pentadactyl limb)- this suggests that organisms descended/evolved from a common ancestor- these structures are called homologous structures

5.4.3 State that populations tend to produce more offspring than the environment can support.

5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival.

Overproduction of offspring is called overpopulation. When this happens there is competition for survival in a species because it limits resources. Those most suited and adapted for their environment survive; survival of the fittest.

5.4.5 State that members of a species show variation.

5.4.6 Explain how sexual reproduction promotes variation in species.

Sexual reproduction leads to variation in species. This is because of meiosis, which allows a huge variety of genetically different gametes to be produced

by each individual. Also fertilization promotes variation in species because fertilization allows alleles from two different individuals to be brought

together in one new individual.

Emily O’BrienA4

5.4.7 Explain how natural selection leads to evolution.

o Populations of living organisms tend to increase exponentially, yet the number of organisms in a population remains constant, on the whole. This is because overpopulation occurs, and the environment is unable to support the number of offspring produced. This causes a struggle for existence in which some die and others live.

o Member in a species have distinct variations which allow some individuals to be better adapted to their environment than others. Through this, natural selection occurs; the better-adapted individuals survive and reproduce.

o Much variation is heritable. Therefore, the better-adapted individuals pass on their characteristics to more offspring. As one generation follows another, the characteristics of the species gradually change, and the species evolves.

5.4.8 Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria.

1. Antibiotic resistance- A gene that gives resistance to an antibiotic is transferred to a bacterium by means of a plasmid- Doctors use the antibiotic to control bacteria, but natural selection favors the antibiotic-resistant bacteria and kills the non-resistant bacteria- The antibiotic-resistant bacteria reproduce and spread, replacing the non-resistant ones. Eventually, most of the bacteria are resistant. - Doctors create another antibiotic, but bacteria grow resistant to that one as well, etc. etc.

2. Melanism in Ladybugs- Adalia bipunctata—a ladybug with red wing cases and two black spots; the red coloration warns predators of their unpleasant taste- Melanic forms—with black wing cases—also exist- Because of their dark coloring, these ladybugs have a selective advantage when sunlight levels are low and it is difficult for ladybugs to warm up.- The melanic form was common in industrialized areas of Britain but declined again after 1960, around the time the smoke in Britain’s air began to decline.- The dark coloring had advantages in the smoke, but without the smoke, the warning coloration is more important for survival.

5.5 Classification

5.5.1 Outline the binomial system of nomenclature.

Emily O’BrienA4

o In the classification of living organisms, the basic group is the species, and each species is classified into a genus.

o Each species needs an international name, so that biologists throughout the world can refer to it. The naming of species is called nomenclature, and the nomenclature that biologists use is called the binomial system because two names are used to refer to each species.

o The first name is the genus name, and it is capitalized.o The second name is the species name, and it is lowercased.o Italics are used when the name is printed and underlined if

hand-written.

5.5.2 List seven levels in the hierarchy of taxa using an example from two different kingdoms for each level.

(Humans) (Coast Redwood)

Kingdom: Anamalia Plantae

Phylum: Chordata Coniferophyta

Class: Mammalia Pinopsida

Order: Primates Pinales

Family: Hominidae Taxodiaceae

Genus: Homo Sequoia

Species: sapiens sempervirens

5.5.3 Distinguish between the following phyla of plants, using simple external recognition features:

Bryophytes—mosses- no roots, only rhizoids; simple leaves and stems- maximum height = 0.5 meters- reproduces by spores

Filicinophytes—ferns- roots, leaves, and short non-woody stems- the leaves are usually curled up in bud and are often pinnate (divided into

pairs of leaflets)- maximum height = 15 meters- reproduces by spores

Coniferophytes—conifers

Emily O’BrienA4

- shrubs or trees with roots, leaves, and woody stems- narrow leaves with a thick waxy cuticle- maximum height = 100 meters- reproduces through seeds, developed from ovules on the surface of the

scales of female cones

Angiospermophytes—flowering plants

- very variable but usually have roots, leaves, and stems- the stems of flowering plants that develop into shrubs and trees are woody- maximum height = 100 meters- reproduces through seeds, developed from ovules inside ovaries (part of

the flowers); fruits develop from the ovaries, to disperse the seed

5.5.4 Distinguish between the following phyla of animals, using simple external recognition features:

Porifera—sponges - no clear symmetry- attached to a surface- pores through body- no mouth or anus

Platyhelminths—flat worms (planaria, tapeworms, liverflukes)- bilaterally symmetric- flat bodies- not segmented- mouth but no anus

Mollusca—mollusks (slugs, snails, clams, squids)- muscular foot and mantle- shell usually present- segmentation not visible- Mouth and anus

Cnidaria—stingers (jellyfish, corals, sea anemones)- radially symmetric- tentacles- stinging cells- mouth but not anus

Annelida—segmented worms (earthworms, leeches, ragworms)- bilaterally symmetric- bristles often present- segmented- mouth and anus

Emily O’BrienA4

Arthropoda—segmented (insects, spiders, crabs, millipedes)- bilaterally symmetric- exoskeleton- segmented- jointed appendages

5.5.5 Apply and design a key for a group of up to eight organisms.

DICHOTOMOUS KEY ASSIGNMENT

Emily O’BrienA4

TOPIC 6: HUMAN HEALTH AND PHYSIOLOGY

6.1 Digestion

6.1.1 Explain why digestion of large food molecules is essential.

Digestion is necessary because humans eat food which contains substances made by other organisms. Therefore, it is not suitable for human tissue and must be broken down to be suitable for humans.

6.1.2 Explain the need for enzymes in digestion.

Since much food is too large to be broken down in the small intestine, these large molecules must be broken down before entering the small intestine. This is called ingestion (eating) and digesting. Digestion occurs at a very slow rate however, and enzymes are essential to speed up the process.

6.1.3 State the source, substrate, products, and optimum pH conditions for one amylase, one protease, and one lipase.

Amylase – Salivary Amylase- source: salivary glands- substrate: starch - product: maltose (disaccharide)- pH: 7

Protease – Pepsin- source: stomach wall- substrate: proteins- product: small polypeptides- pH: 1.5

Lipase – Pancreatic Lipase- source: pancreas- substrate: lipids- product: 3 fatty acids and 1 glycerol- pH: 7

6.1.4 Draw and label a diagram of the digestive system:

Emily O’BrienA4

6.1.5 Outline the function of the stomach, small intestine, and large intestine.

Stomach- begins the digestion of proteins (pepsin)- acid conditions kill bacteria- acidity = excellent for pepsin- digestion is completed by enzymes secreted from the wall of the small

intestine

Small Intestine- products of digestion absorbed by the villi- the indigestible parts of food and a large volume of water pass into the large intestine

Large Intestine- water is absorbed, leaving solid feces, which are egested through the anus

6.1.6 Distinguish between absorption and assimilation.

Absorption = food is absorbed through the villi in the small intestine into the bloodstream

Assimilation = food becomes part of the tissues of the body

6.1.7 Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.

o The folds increase the surface area over which food can be absorbed (microvilli = even more surface area!)

o The epithelium is only one cell layer thick – less distance for food to travel

o Protein channels in microvilli increases the rate of absorption through active transport (ATP provided by mitochondria)

o Blood capillaries decrease diffusion distance

6.2 The Transport System

6.2.1 Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves, and the route of blood through the heart.

Emily O’BrienA4

6.2.2 State that the coronary arteries supply heart muscle with oxygen and nutrients.

6.2.3 Explain the action of the heart in terms of collection blood, pumping blood, and opening and closing of valves.

The atria collect blood from the veins; they contract, the A-V valves open, and the blood is pushed into the ventricles. The semi-lunar valves are closed, so the

ventricles fill with blood. The walls of the ventricles contract, and this rise in pressure causes the A-V valves to close (preventing back-flow) and the semi-lunar valves to open. Blood is pumped out of the ventricles through the

arteries.

6.2.4 Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain, and epinephrine

(adrenaline).

The heart does no need a nerve to stimulate its beat, and is therefore called myogenic. Instead, the heart’s beat is controlled by the pacemaker, which Is located on the wall of the right atrium. The pacemaker can receive messages

from nerves or hormones telling it to speed up or slow down. For example, there is specific nerve that is sent from the brain to the pacemaker telling it to speed

up, and there is another specific nerve sent from the brain to the pacemaker telling it to slow down. Also, the hormone adrenaline causes the pacemaker to speed up as well.

6.2.5 Explain the relationship between the structure and function of arteries, capillaries and veins.

Arteries- move blood away from heart- have thick, outer layers of longitudinal collagen and elastic fibers to avoid bulges/leaks- thick layers also create high pressures and maintain high speeds

Veins- bring blood to the heart- thin layers to accommodate slow-moving blood and low pressure- thin walls allow the vein to be pressed flat against adjacent muscles- little danger of bursting- NB veins have valves to prevent back-flow

Capillaries- very, very small; one cell layer thick- many small capillaries have a larger surface area than fewer wider ones

because of folds- pores between cells in the wall allow some of the plasma to leak out and

form tissue fluid

Emily O’BrienA4

6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes (red and white blood cells), and platelets.

6.2.7 State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibiotic, urea, and heart.

6.3 Defense Against Infectious Disease

6.3.1 Define pathogen.

Pathogen—an organism or virus that causes disease

6.3.2 Explain why antibiotics are effective against bacteria but not against viruses.

Antibiotics shut down the systems and processes in a bacteria cell. However, viruses do not have systems (they are not cells), so antibiotics are not

effective against them.

6.3.3 Outline the role of skin and mucus membranes in defense against pathogens.

Skin—a physical barrier against disease

Mucus Membranes—glands secrete lactic acid and fatty acids to make the surface of the skin acidic; the mucus contains lysozyme, an enzyme that

destroys bacterial cell walls (the body’s antibiotic)

6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissue.

Phagocytes—cell eaters- these cells identify pathogens and ingest them by endocytosis; they are then digested by the cells lysosomes- Phagocytes can ingest pathogens in the blood; they can also squeeze

through walls of capillaries and move through tissues to sites of infection

6.3.5 Distinguish between antigen and antibodies.

Antigen—foreign substances that stimulate the production of antibodies; this includes cell walls of bacteria or fungi and protein coats of viruses

Antibody—proteins that recognize and bind to specific antigens and flag it for death in order to defend the body against pathogens

6.3.6 Explain antibody production.

1. Antibodies are made by lymphocytes (a type of white blood cell)2. A lymphocyte can only make one type of antibody, so a huge number

of different lymphocyte types are needed. Each lymphocyte puts some

Emily O’BrienA4

of the antibody that it can make into is cell surface membrane with the antigen-combining site projecting outwards.

3. When a pathogen enters the body, its antigens bind to the antibodies in the cell surface membrane of one type of lymphocyte.

4. When antigens bind to the antibodies on the surface of a lymphocyte, this lymphocyte becomes active and divides by mitosis to produce a clone of many identical cells.

5. The clone of cells starts to produce large quantities of the same antibody—the antibody needed to defend the body against the pathogen.

6.3.7 Outline the effects of HIV on the immune system.

The HIV virus virtually shuts down the immune system and causes AIDS.

6.3.8 Discuss the cause, transmission, and social implications of AIDS.

AIDS, or acquired immunodeficiency syndrome, is an acquired disease; it is not hereditary. It is caused by the HIV virus, and it can be transmitted through sexual intercourse, childbirth, or breast-feeding. There are many social implications of AIDS. For example, people with AIDS may be shunned because people are so

fearful of getting the disease. Also, it can make families very poor because medication for it is expensive. Of course, it also causes much grief to family

and friends of those with AIDS because of the low survival rate.

6.4. Gas Exchange

6.4.1 Distinguish between ventilation, gas exchange, and cell respiration.

Ventilation—the process of bringing fresh air to the alveoli and removing stale air

Gas Exchange—swapping one gas for anotherCell Respiration—process of transforming chemical energy (glucose) into

ATP in the mitochondria

6.4.2 Explain the need for a ventilation system.

Humans need to take in Oxygen and release Carbon Dioxide. Oxygen diffuses from the air into the blood, and Carbon Dioxide diffuses in the opposite

direction (due to concentration gradients). In order to maintain concentration gradients, the air in alveoli must be refreshed frequently.

6.4.3 Describe the features of alveoli that adapt them to gas exchange.

o Each alveolus is small, but the lungs contain hundreds of millions of alveoli, covering a huge surface area.

o The wall has a single layer of very thin cells in order to make diffusion quicker.

Emily O’BrienA4

o The alveoli are covered by a dense network of blood capillaries with low Oxygen and high Carbon Dioxide concentrations; Oxygen diffuses into the blood and Carbon Dioxide diffuses out.

o Cells in the alveolus wall secrete a fluid which keeps the inner surface of the alveolus moist, allowing the gases to dissolve and prevents the sides of the alveoli from sticking together.

6.4.4 Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles, and alveoli.

6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm, and abdominal muscles.

Inhaling

1. The external intercostal muscles contract, moving the ribcage up and out

2. The diaphragm contracts, becoming flatter and moving down3. These muscle movements increase the volume of the thorax4. The pressure inside the thorax therefore drops below atmospheric

pressure5. Air flows into the lungs from outside the body until the pressure

inside the lungs rises to atmospheric pressure

Exhaling

1. The internal intercostal muscles contract, moving the ribcage down and in

2. The abdominal muscles contract, pushing the diaphragm up into a dome shape

3. These muscle movements decrease the volume of the thorax4. The pressure inside the thorax therefore rises above atmospheric

pressure5. Air flows out from the lungs to outside the body until the pressure

inside the lungs falls to atmospheric pressure

Emily O’BrienA4

6.5 Nerves, Hormones, and Homeostasis

6.5.1 State that the nervous system consists of the central nervous system (CNS) and the peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses.

6.5.2 Draw and label a diagram of the structure of a motor neuron.

6.5.3 State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.

6.5.4 Define resting potential and action potential (depolarization and repolarization).

Resting Potential—the electrical potential across the plasma membrane of a cell that is not conducting an impulse; neurons pump sodium ions out and potassium ions in, and concentration gradients are established; the inside therefore has a net negative charge

Action Potential—the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it

(depolarization and repolarization); when an impulse passes along the neuron, sodium and potassium ions diffuse across the membrane through ion channels; the electrical potential across the membrane is reversed (depolarization), then restored (repolarization)

6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron.

1. An action potential in one part of a neuron causes an action potential to develop in the next section of the neuron. This happens because of the diffusion of the sodium ions between the region with action potential and region with resting potential. These ion movements reduce resting potential. When the potential rises above the threshold level, the channels open.

2. Depolarization occurs. Sodium ions diffuse into the neuron. This reduces membrane potential, causing more sodium channels to open and a reversal of charges.

3. Repolarization occurs. Potassium channels open. Potassium ions diffuse out of the neuron. By the positive ions exiting, the inside of the neuron restores its net negative charge.

Emily O’BrienA4

4. Active transport of sodium and potassium ions across the membrane restores the concentration gradients and the resting potential.

6.5.6 Explain the principles of synaptic transmission.

1. A nerve impulse reaches the end of the pre-synaptic neuron.2. Calcium diffuses through calcium channels into the pre-synaptic

membrane because of depolarization of the pre-synaptic membrane3. Vesicles of neurotransmitters move to the membrane and release

their contents (exocytosis).4. Neurotransmitter diffuses across the synaptic cleft and binds to

receptors.5. Sodium ions enter the post-synaptic neuron and cause depolarization6. Nerve impulse continues setting off along the post-synaptic neuron7. Calcium is pumped out. Neurotransmitter is broken down in the cleft

and reabsorbed into the vesicles.

6.5.7 State that the endocrine system consists of glands that release hormones that are transported in the blood.

6.5.8 State that homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature, and water balance.

6.5.9 Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanism.

In feedback systems, the level of a product feeds back to control the rate of its own production. Negative feedback has a stabilizing effect because a change

in levels always causes the opposite change. A rise in levels feeds back to decrease production and reduce the level. A decrease in levels feeds back to increase production and raise the level.

6.5.10 Explain the control of body temperature, including the transfer of heat in blood, and the roles of the hypothalamus, sweat glands, skin arterioles, and shivering.

Response to Chilling:

1. Skin arterioles narrow so that less blood flows through them. 2. Temperature of the skin falls, so less heat is lost to the environment.3. Sweat glands do not secrete sweat, and the skin remains dry.4. Temperature returns to normal.

OR…1. Skeletal muscles contract rapidly, causing shivering, which generates

heat.2. Temperature returns to normal.

Response to Overheating:

Emily O’BrienA4

1. Skin arterioles widen so that heat transfers from the core to more of the body.

2. Temperature of the skin rises, so more heat is lost to the environment.3. Sweat glands secrete large amounts of sweat, and the skin remains

damp.4. Sweat evaporates, which has a cooling effect because of water’s high

heat of vaporization.5. Temperature returns to normal.

OR…1. Skeletal muscles remain relaxed, so no additional heat is generated.2. Temperature returns to normal.

6.5.11 Explain the control of blood glucose concentration, including the roles of glucagon, insulin, and Alfa and Beta cells in the pancreatic islets.

Response to Low Blood Glucose:

1. Pancreas sends a message to the brain to feel hungry.2. Glucose level in the blood rises to normal.

OR…1. Pancreas sends a message to islet Alfa cells to produce glucagon.2. This stimulates the liver to convert glycogen to glucose—which is

released into the blood (hydrolysis reaction).3. Glucose level in the blood rises to normal.

Response to High Blood Glucose:

1. Pancreas sends a message to the brain to feel full.2. Glucose level in the blood falls to normal.

OR…1. Pancreas sends a message to islet Beta cells to produce insulin.2. Muscle and liver cells convert blood glucose to glycogen (dehydration

synthesis). 3. Glucose level in the blood falls to normal.

6.5.12 Distinguish between type I and type II diabetes.

Type I Diabetes:- onset is usually during childhood- Beta cells produce insufficient insulin

Emily O’BrienA4

- insulin injections are used to control glucose levels- diet cannot control the condition by itself

Type II Diabetes:- onset is usually after childhood- target cells become insensitive to insulin- insulin injections are not usually needed- low carbohydrate diets usually control the condition

6.6 Reproduction

6.6.1 Draw and label diagrams of the adult male and female reproductive systems.

Emily O’BrienA4

6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormone), estrogen, and

progesterone.

FSH—stimulates the development of follicles—fluid filled sacs that contain an egg cell; produced by the pituitary gland

LH—stimulates follicles to become mature, release their egg (ovulation), and then develop into a structure called the corpus luteum; produced by the

pituitary gland

Estrogen/Progesterone—stimulate the development of female secondary sexual characteristics during puberty; they also stimulate the development of the uterus lining that is needed during pregnancy; produced by the ovary

6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation, and thickening of the endometrium.

6.6.4 List three roles of testosterone in males.

o The development of the testeso Causes male secondary sexual characteristics to developo Maintain sex drive

6.6.5 Outline the process of in vitro fertilization.

1. A drug is injected once a day for three weeks, to stop the woman’s normal menstrual cycle.

2. Large doses of FSH are injected once a day for 10-12 days to stimulate the ovaries to develop many follicles.

3. HGG (another hormone) is injected 36 hours before egg collection, to loosen the egg in the follicles and to make them mature.

4. The eggs are extracted from the follicles using a device inserted through the wall of the vagina.

5. Each egg is mixed with provided sperm in a shallow dish; the dishes are kept overnight in an incubator.

6. The dishes are checked to see if fertilization has worked.7. Two or three embryos are selected and placed, via a long plastic tube,

into the uterus.8. A pregnancy test is done to see if any embryos have implanted.

Emily O’BrienA4

9. A scan is done to see if the pregnancy is continuing normally.

6.6.6 Discuss the ethical issues associated with IVF.

For IVF:- Many forms of infertility are due to environmental factors, so offspring will

not inherit them- Any embryos that are killed during IVF are unable to feel pain or suffer,

because their nervous system has not developed- Parents willing to go through the process of IVF must have a strong desire

for children and so are likely to be loving parents

Against IVF:- Inherited forms of infertility might be passed on to children, which means

that the suffering of the parents is repeated in their offspring- More embryos are often produced than are needed and the spare embryos

are sometimes killed, denying them the chance of life- IVF is an unnatural process, carried out in laboratories, in contrast to

natural conception occurring as a result of an act of love