Genetics and Evolution Summary Notes

8/10/2019 Genetics and Evolution Summary Notes

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Genetics and Evolution Summary Notes

Describe the process of meiosis. Meiosis is the process of sex cell formation. (1)

MITOSIS MEIOSIS

Function Mitosis is the process of normal cell

division.

Growth :multi-cellular organismsgrow in size and complexity bymaking more cells

Repair:old and damaged cells arecontinuously replaced by the divisionof cells

Genetic Stability:Daughter cells

contain same number and kind ofchromosomes as the parent cell.

For sexual reproduction. Occurs in

the testes and ovaries. It produces

the gametes. There are two types of

gametes. Egg cells and sperm cells.

When does it

happen?

Mitosis occurs only in eukaryotes. When the sperm and the egg unite.

Where does it

happen?

Mitosis occurs in most cells Sex cells

How many cell

divisions?

1 cell division 2 divisions

How many cells? 2 cells. (two daughter cell swish thesame chromosome number as theparental cell.

4 cells

How many

chromosomes?

46 chromosomes each 23 chromosomes

Is there variation

in offspring?

Mitosis is the copying of cells.

Sometimes there might be an errorafter the egg fertilization.

There is variation because the

chromatids exchange DNA sections.

Uses and results of

their use

Mitosis is the process by which allcells divide. Many cells have a limited

life span, and mitosis allows them tobe renewed on a regular basis. Mitosisis also responsible for generating themany million of cells that are neededfor an embryo to develop into a foetus,an infant, and finally an adult.

Meiosis functions to reduce thenumber of chromosomes to one half

.Each daughter cell that is producedwith have one half as manychromosomes as the parent cell.Meiosis is important in assuringgenetic diversity in sexualreproduction.


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I denti fy genes as uni ts of heredity (carr iers of genetic information). (2)

- A geneis a unit of heredity in a living organism. It is normally a stretch of DNA that codes

for a type of protein.

Descri be the structure of DNA in terms of f our bases; the double stranded backbone, and thedouble helix shape. (3)

DNA - Deoxyribonucleic acid

- DNA carries the genetic informationand passes it from one generation to the next. DNAcarries the codeto make proteins(that contribute to determining eye colour and hair colour)to enable the cell to reproduce and perform its function.

The Double helix

- In 1953, James Watson, Francis Crick and Rosalind

Franklin discovered that the structure of DNA was adouble helix

Structure:

- Two strands intertwine like a spiral staircase to form a

structure called a double helix.- Sides: Deoxyribose sugar and a unit of phosphate

forms the upright supports along the sides. Each sugar

joins with a base.- Bases form the rungs of the staircase- The sugar (deoxyribose) + phosphate + a base = a

nucleotide.

Outl ine the connection between chromosomes, genes and DNA and part icularl y identi fy that

in formation i s transferred as DNA when cell s reproduce themselves and explain the

advantages of DNA repli cating exactly. (4)

ABOUT: Chromosomes, Genes and DNA

- Within each cell is a nucleuswhich controls all the activities of the cells.- Inside the nucleus of each of your cells is your unique set of 46 chromosomes.- Each of these is a long, thread-like structure made up of DNA (deoxyribonucleic acid).- Sections of DNA on the chromosomes that contain complete messages are called genes.- The message in a gene is a coded formula needed by the cell to produce one protein. E.g.

hair.- The DNA molecule is made up of simple bases called nucleotides.

Base Matching base

Adenine Thymine

Guanine Cytosine

Thymine Adenine

Cytosine Guanine


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- Each nucleotide is made up of three chemical groups: a Sugar, a Phosphate,and a Base.- The order in which the bases are strung along the chain forms the basis of the genetic code.

Appreciate the role that envir onmental factors have in determining the featur es of an

organism. (5)

The environment plays a big role in the appearance of an organism. The environment includes allsurrounding forces of an organism, such as diet, nutrition, climate, exposure to disease. It canaffect the expression of genes. Identical genotypes (twins) do not always produce the samephenotypes because the environment can affect the expression of genes.

Example:

Identical twins have exactly the same genes, such as for tall height and strong muscles. If onetwin is brought up in a poor family he may eat very little, be thin, not very tall, he may sufferfrom malnutrition resulting in rickets (bandy legs), scurvy (vitamin C deficiency), and poor teeth,he may be unable to play sport. If the other twin is brought up on a good nutritious diet in a

wealthy family he may reach his full height, be fit and strong with good legs and teeth, or if hewas brought up on hamburgers and chips he maybe obese.

Environmental Factors influencing your phenotype:

- Diet- Nutrition- Exposure to disease- Climate- Temperature- Sunlight

Environmental Factors promoting Cancer

- Smokinglung cancer- Drinkingliver cancer- Exposure to UV lightskin cancer- Exposure to radiationthyroid caner

Environmental Factors promoting rickets

Vitamin D is found in fish and vegetables. When the sun shines on our skin we can also make

vitamin D. When children do not get enough vitamin D, the bones in their legs bend, this iscalled rickets.

Plants

Climatic factors - such as rainfall, temperature or exposure to wind - can be important, as well assoil composition and the availability of nutrients.

What affects the growth of plants:

- availability of water- nutrition in the soil- availability of sunlight- fertilisers- climate


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Examples:

- The pH of soil can affect the hydrangea plant.- Those grown in acidic soil produce blue flowers whilst those grown in basic soil produce

pink flowers

Distinguish between a gene and an al lele. (6)

A gene is a unit of heredity and is a section of DNA whereas, alleles refer to different versions ofthe same gene (e.g. if the height will be short or tall)

Defi ne dominant and recessive genes and explain their inf luence in determining phenotype

given the inher ited genotype. (7)

DOMINANT:The genes which determines the physical traits of a person. They dominate overrecessive genes.RECESSIVE:A recessive gene is a gene that produces an effect in the organism only when it is

homozygous, having identical alleles for a single trait.

Genotype:

- Refers to the genetic traits in an organism.- It has to do with the genetic coding of an organism. =- Such coding is inheritable.- The genotype is the genetic load that is copied every time a cell divides, and therefore isinheriteddown to the next generation.

Genotypeis something you can't see with your eyes (e.g.. dominant, recessive, heterozygous).

Phenotype:

- Refers to observable, physical manifestations of an organism.- The phenotypeincludes physical characteristics, behaviours corresponding to suchspecies, structures, organs, behaviours, reflexes, etc.

Phenotypeis things that can be seen with your eyes. (ex. colours, growth).

The genotypeis the genetic programmingthat provides the phenotype.

Define biotechnology and explain that genetic engineer ing is a form of biotechnology. (8)

Biotechnology - Biotechnology is the practice of using plants, animals and micro-organisms suchas bacteria, as well as biological processes - such as the ripening of fruit or the bacteria that breakdown compost - to some benefit.

Genetic Engineering - the deliberate modification of the characteristics of an organism bymanipulating its genetic material to improve certain characteristics.

Outl ine the engineering of pest resistance in to cotton plants or the production of human

insul in by bacteria as examples of genetic engineering. Use these as examples of where

developments in Science have led to new technologi es. (9)

When the gene is inserted into cotton plants, they produce toxic proteins called Bt toxins that killthe bollworm caterpillars. The poison stays in the leaves and does no harm until the bollworm


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eats the leaf tissue. It is very specific - it only kills bollworm caterpillars and very closely relatedspecies. It does not affect humans or other animals.

The production of insulin by bacteria, by inserting the human gene for making insulin into

the DNA of a bacterium.People who are diabetic need supplies of insulin because their pancreas does not naturally makeit. Insulin is needed to keep the amount of glucose in your blood at the right level. People withdiabetes need to be given daily injections of insulin to keep their blood glucose levels correct.Medical insulin was formerly extracted from the pancreases of pigs which were slaughtered formeat, but now it can be produced in vast amounts in the lab from bacteria which have had thehuman insulin gene inserted into its DNA.

The genefor insulin can be removed from a chromosome in a human pancreascell using anenzyme which cuts out the exact piece of DNA containing the gene. The gene can then betransplanted into bacteriawhere it combines with the microbes DNA to turn the bacteria intotiny factories for making insulin. As the bacteria reproduce by mitosis, making exact copies ofthemselves (identical DNA) the new bacteria contain the human insulin gene. The bacteria being

used is Escherichia coli (E coli).

Discuss how dif ferent groups within society or di ff erent cul tur es may have dif ferent views

about biotechnologies. (10)

I denti fy choices that need to be made when consideri ng whether to use parti cular scientif ic

advances such as GM crops, human cloni ng, and embryoni c stem cell s. (11)

GM CropsAdvantages:

- Crops are more productive and have a larger yield.

- Could potentially offer more nutrition and flavour (although this is debated).

- A possibility that they could eliminate allergy-causing properties in some foods.

- Inbuilt resistance to pests, weeds and disease.

- More capable of thriving in regions with poor soil or adverse climates.

- More environment friendly as they require less herbicides and pesticides.

- Foods are more resistant and stay ripe for longer so they can be shipped long distances or

kept on shop shelves for longer periods.

Group For Against

Scientist -Not harmful

-Resistant to

disease

-Continuity of

species

-Pests evolve resistance to

GM crop e.g. BT cotton

Citizen-

But with labelling-

Destroying children-Playing with god

-Allergies unknown

Activist -Answer to solving

word wide food

shortage e.g.

golden rice

-

Activist against GM - -Control food productivity

MONSANTO


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- As more GMO crops can be grown on relatively small parcels of land, they are an answer to

feeding growing world populations.

Issues:- Should be encouraged without research into the risks- Not labelling is wrong and unfair to consumers-

GM crops pose a risk to food diversity- Could give rise to super-weeds and super-pests- GMO technology companies patent their crops- Interferes with traditional agricultural methods

Human CloningAdvantages:

- Can mas produce animals with desirable characteristics- Producing animals that have been genetically engineer to provide human products, such

as insulin for organs or transplants- Producing human embryos to supply stem cells for therapy

Ethical Issues:

-Raises issues of how far humans should be allowed to interfere with the production ofnew life

Embryonic Stem CellsAdvantages:

- Form tissues and cells for medical therapies- Potential to reverse diseases- Able to produce new and healthy tissues for transplant- New drugs can be tested on stem cells prior to animals and humans

Ethical Questions:- Does life begin at fertilization, in the womb, or at birth?- Is a human embryo equivalent to a human child?

-Does a human embryo have any rights?

- Might the destruction of a single embryo be justified is it provides a cure for a countlessnumber of patients?

L ist uses of biotechnologycould include: (12)

- AI (Artificial Intelligence)- IVF (InVitro Fertilisation)- GM foods- Production of human insulin

Put f orward a case for and against the use of biotechnology.(13)

ADVANTAGES of biotechnology:

Different genes can be combined to make something better

Can be enriched with vitamins to increase health

Use of stem cells to treat diseases

Diagnosing genetic disorders

DISADVANTAGES of biotechnology:

May trigger allergic reactions

Many GM crops have pesticides built in themtoxic insects Moral and ethical issues surrounding cloning


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I denti fy scientif ic skil ls that can be usefu l in a broad range of careers. (14)

- Computer skills (ICT)- Critical thinking- Reading and writing- Fine motor skills

-Ability to follow instructions

- Observation- Cognitive abilities- Determining and minimising risks- Examination and evaluating

experiments- Drawing conclusions from evidence- Analysis of results

- Measure accurately- Performing under pressure- Making judgements- Graphing results

-Teamwork

- Attention to detail- Mathematics- Collection of data- Writing an experimental report- Application of knowledge- Organisations

I denti fy possible career paths in science. (15)

-

Cancer research- Bioengineer- Mathematical ecologist- DNA sequencing facility manager

-

Plant research- Examiner of patents- Forensic scientist- Immunologist

Wr ite arguments for and against assisted reproduction or genetic engineering. (16)

Group Arguments for genetic engineering: Arguments against genetic engineering

Lab - Could have health benefits forexample golden rice has a sourceof vitamin A that could help

reduce blindness.

-Cancer-fighting genes can beintroduced to foods such astomatoes and broccoli.

- GM foods can improve the

nutrition of people who do nothave enough to eat.

- Might trigger allergic reactions orheightened allergic reaction e.g. a nutgene inserted into another organism

- Set high prices which people wont be

able to afford e.g. Monsanto settinghigh prices for their seeds making itunaffordable for farmers

Trial - GM soy is resistant to herbicide-farmers can spray weeds withoutharming their crops

- Genetic modification might beable to increase the health andcooking properties of soy

products.- Some GM crops have pesticide

built into them, so farmers wonthave to add chemicals

- Australian experiments indicatethat some GM crops reduce the

use of pesticide by up to 75%- Pesticides previously used may be

washed into and contaminate

water

- Non-target insects such as bees andbutterflies may be killed by the plants

- Birds that eat poisoned insects may dieas well

- Insects can build up a resistance topesticides

-GM foods not only deprives insects oftheir source of food, but also affectsthe whole food chain. Animals thatdepend on insects for food might

starve e.g. if all the ball worms thatfeed on BT cotton die off, animals that

rely upon that insect die too

GM

Farm

- Greater ability to tolerate disease-

higher yields- Greater ability to tolerate drought-

- Many Australians are reluctant to eat

GM foodthere are no long termresults to prove its safe


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higher yields- Greater ability to tolerate frost-

higher yields- Higher yields- more profit

- Multinational food companies willpatent GM seeds to control the price

- Since farmers will depend on thecompanies for seeds, they will have to

pay whatever price the companiesdemand.

Analyse the accuracy of scientif ic i nformation in the mass media. (17)

The data in a source is valid if:- They have been fathered using appropriate methods- They relate to the hypothesis or problem

A secondary source is reliable if:- The information is not biased- It has been written by a qualified person

-It is on a reputable site, i.e. .gov .edu

- It is current- It refers to data and statistics from valid first-hand investigations

The information in a source is accurate if:- The information can be substantiated in more than one reliable source

Discuss the role of mutati ons in the abil ity of species to adapt to changing envi ronments and

the consequences for natural selection. (18)

Mutations are a change in the structure of DNA, some mutations can be beneficial to an

organism. When an environmental changes, organisms with beneficial mutations are more likely

to survive. These organisms reproduce, passing on their beneficial mutations. Over time, thespecies adapts better.

Triggers for mutations:- Light- Chemical exposure- Radiation exposure

Defi ne adaptations and discuss their role in species and individual survival. (19)

Adaptations: The features which enable the organisms to live in specific environment.

- If an organism is not adapted to its environment, it will die.

-Therefore, when the environment goes through physical changes, the organisms which livethere must adapt to the new conditions to survive.

- However, due to natural selection, not all species undergo adaptations.- Adaptations can be behavioural, physiological and physical.

Define biodiversity and discuss its role in the health of an envir onment and the survival of li fe.

(20)

Biodiversity: variety and differences amongst living organisms.

- For evolution to occur there must be genetic differences amongst the members of a species(i.e. the population).

-

Biodiversity in genes are important for the survival of a species.- A particular genetic make-up may be very successful at a certain time in Earth's history.


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- If the environment begins to change, however, this genetic make-up may no longer be

successful.- Genetic diversity plays a role in safeguarding a species from extinction when the

environment changes.

Discuss evidence that present day organi sms have developed fr om dif ferent organi sms in the

past. Include fossil , biogeographi cal, comparative embryonic, comparati ve anatomic and

comparative DNA evidence. (21) Develop ideas of common ancestor. (22)

FossilsA fossil is a remnant or trace of a once living organism. Usually it is the hard parts ofplants and animals that are presence e.g. wood, bones or shells. Fossils are preserved by being

covered in sediments or by falling into an environment where there is little oxygen.

Fossils are present in rocks found hundreds or thousands of years ago. Some animals that were

around during these time periods were fossilised. Through the ages of the rocks, scientists see thechanges that have occurred in different species to adapt to their environment, known as evolution.

Transitional Forms

Many fossils have been found which appear to have the characteristics of two different groups oforganisms. These are called transition fossils. The evolution from ancient reptiles to mammals iswell documented by a series of transition fossils. Two of the most famous transition fossils arearchaeopteryx, which provides evidence for the common ancestry of birds and reptiles, and the

lobe-fin fish, which indicates that amphibians may have evolved from fish.

Archaeopteryxsimilar to an extinct group of dinosaurs, the theropods, except it had feathers

and a wishbone

Lobe-fin fishA comparison of the skeletons of a lobe-fin fish and a primitive amphibianreveals and extraordinary similarity. The lobe-fin fish had lungs but in the amphibian, larger ribs,pelvis and limb bones have evolved for support on land.


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Transitional forms provides evidence to scientists about the mix between two species, this mixhas occurred to support the animals for them to adapt to environmental change.

Biogeography

Biogeography is the study ofliving things in relation togeographical regions. Darwinand Wallace usedbiogeography as evidence ofevolution. They noticed thatspecies living in the samearea were more similar toeach other than to speciesliving in similar habitats farapart. This shows that speciesevolved due to the selectivepressure in their own habitats

Comparative Embryology

The different embryology supports evolutionbecause it shows scientists the similarities in thespecies and how theyve changed. Thesimilarities show us that all the species may have

branched from one organism.

Homologous Structures

The anatomy of different species can be

compared to look for evidence of evolution from

a common ancestor.


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Homologous structures are structures found in plants or animals that have the same origin, butnot necessarily exactly the same form or the same function.

The development of homologous structures is an example of divergent evolutionwhich occurswhen a number of species develop from one common ancestor, becoming less and less alike overtime due to their different habitats.

The pentadactyl limbs of vertebrateanimals are examples of homologousstructures. All of these groups have limbswith five digits (finger-like structure_which have the same basic structural plan,but have altered to different environmentsand life-styles.

This suggests that all of these groups of animals originated from some original group of animals(the commonancestor)

Comparative DNA

Science have found that DNA and the proteins it produces can provide evidence about evolution.If 2 new species evolved from a common ancestor, their DNA and protein molecules slowlychange and become different. The number of differences is proportional to the time since they

separated and allow the construction of evolutionary trees.

DNA and other biochemical evidence can be used to check the accuracy of evolutional treesalready worked out from fossils or from the study of structural homologies. The biochemicalsimilarities between organisms can indicate to scientists that organisms could have the same

ancestor and hence, the difference species that exist today are evidence for evolution.


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Outl ine the theory of evolution by natural selection. Outli ne how Charl es Darwin constructed

thi s theory to explain his observations. (23)

NATURAL SELECTION:

- In all populations of living things there are differences (biologists call them variations)

within the offspring.- Some offspring will be better suited to survival than others.

- When an animal is born with a slight advantage and is more likely to survive than its

brothers and sisters.

-Darwin summarised his theory of natural selection in 4 steps:

-1. Members of a single species show variation in their characteristics. Some of this variationis passed from parent to offspring (i.e. it is inherited).

-2. More of each kind of organism is produced than can survive to maturity. Some members ofa species will die before they reproduce.

-3. The surviving members of a species possess the characteristics that best enable them tosurvive in their present environment. They pass these characteristics on to their offspring.

-4. Over time, organisms become better suited to their current environment.

Descri be the diff icult ies that the theory of evolution had in gaini ng acceptance in society. (24)

- His theory started a controversy between the biblical belief that all organisms were formed atthe same time.

- The church tried to shame the theory, which led to a debate between the Bishop of Oxford,Samuel Wilberforce and the eminent biologist, Thomas Huxley.

- It was known as the Monkey Debate, and after some time his theory started to be accepted.

L ist the factors that cause natural selection: (25)

- competition for food & shelter

- variation- struggle for existence- reproduction

Explain how the factors causing natural selection can lead to changes in a species. (26)

One example is the peppered moths of north

England. They have a short life span meaning that changes in the population can be seen in just afew years. In the case of the peppered moths, their environment changed rapidly. Peppered mothsare born either pale coloured or nearly black. In areas covered with pale lichen the pale mothswere well camouflaged. They were suited to their environment. The black moths were quicklyeaten by birds. Only a small fraction of black moths survived to lay eggs. When pollution was at

its worst the walls of buildings were black. Then the white moths were eaten, while most of theblack moths survived to lay eggs.

Defi ne art if icial selection and give an example. (27)

-Artificial selection (or selective breeding) describes intentional breeding for certain traits, or

combination of traits.


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- Artificial selection results in reduced genetic diversity because fewer individuals are chosen

for breeding. This results in inbreeding.

EXAMPLE: Early humans chose to breed dogs that were loyal, fast and good at retrieving game,

and so hunting dogs evolved to have these traits.

Descri be an example of how an organi sm has evolved. (28)

The original birds landing on the islands from the mainland would have had some variatione.g.

in their beaks.

Those birds on each island which was most suited(best adaptedor fittest) to theirenvironment (e.g. birds with beaks best suited to the food resources on their island) would havesurvived best.They would also have reproduced best, passing on their successful characteristicsto their

offspring (because of inheritance of genes).

Thus, particular genes and characteristics would have become more commonon the different

islands. Eventually, each group of finches would have become so different that they could be

regarded as separate species.

Distinguish between how Darwin & Lamarck would explain evoluti on. (29)

Lamarcks theory of evolution was that species learnt to change as their environment did. He didnot believe in natural selection where only certain organisms would adapt to its environment,

instead, all organisms changed. However, Darwins theory suggested that the theory of evolutionwas caused by natural selection and the dying out of animals with detrimental qualities.


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