Higher Biology

I needed a way to study so I thought why not make a blog and post notes each day to help me revise!

[higherbiology-blog]

Cell Biology - DNA and Proteins 1

PROTEINS AND AMINO ACIDS

Proteins are large complex molecules. They are made of repeating units called amino acids. There are around 20 different types of amino acids.

PROTEINS AND POLYPEPTIDES

Amino acids are joined together by peptide bonds to form polypeptide chains. A chain then golds to form a completed protein.

PROTEIN STRUCTURE AND FUNCTION

The sequence of amino acids in a protein determines its structure and function.

CLASSIFICATION OF PROTEINS

Proteins can be classed into two groups

Fibrous proteins - shape is flattened

Globular proteins - shape is rounded

ROLE OF PROTEINS

THE FUNCTION OF DNA

DNA carries the complete genetic information of an organism in the form of a code. The sequence of amino acids in a protein is determined by this code.

THE STRUCTURE OF DNA

DNA is a type of nucleic acid called deoxyribonucleic acid. DNA consists of a double helix - two strands twisted into a coil. Each strand is made of repeating units called nucleotides. Each nucleotide is made of a molecule of deoxyribose sugar, a phosphate group and an organic base. There are 4 different bases in DNA - adenine (A), cytosine (C), guanine (G), thymine (T).

A DNA nucleotide

(couldn't be bothered drawing it)

FORMING A DNA STRAND

(did draw this one though)

The sugar of one nucleotide joins with the phosphate of the adjacent nucleotide. This is repeated to form a chain of nucleotides which makes up a single strand of DNA

JOINING TWO STRANDS TOGETHER

Two strands join together to form a molecule of DNA. Only cetain bases can pair together

adenine pairs with thymine

cytosine pairs with guanine

This is known as complimentary base pairing. Weak hydrogen bonds between the complimentary bases hold the strands together.

The two DNA strands twist to form a double helix. The Ribbon-like material wrapped around being the sugar-phosphate backbone and the bars inbetween being the complimentary base pairs.

DNA, GENES AND CHROMOSOMES

DNA is organised into chromosomes. A section of DNA which codes for one protein is called a gene.

[higherbiology-blog]

Answers to Essay Questions - Foraging Behaviour in Animals and Social Mechanisms for obtaining food and for defence

Foraging Behaviour in Animals (4)

Search Time - length of time taken to look for food

Pursuit Time - length of time taken to catch the food

Energy gained from the food must be higher than the energy used in searching and handling the food

To ensure that the maximum energy gain is achieved, animals enploy optimal foraging strategies

Foraging behaviour involves using sense (see, hear, smell) to find food

Social Mechanisms for Obtaining Food and for Defence

Cooperative hunting ensures that all members of the group feed even the weaker ones

By working in groups there is more chance of finding bigger animals to feed on

Dominance hierarchy exists - strongest member at the top and others ranked beneath

This ensures strongest member survives and reproduces passing on his strong genes

Some examples of social mechanisms for defence include:  > Schooling in fish - together in large numbers  > Protective groups - weak individuals in the centre of the group  > Rapid movements to confuse predator - so much movement confuses the predator 

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Answers to Essay Questions - Genetic Engineering and Somatic Fusion

Genetic Engineering (6)

Genes located on chromosomes by gene probes or banding patterns

Endonuclease enzymes used to cut DNA/genes

Plasimids removed AND opened using restriction endonuclease

Genes sealed/inserted into bacterial plasmid using ligase

Altered plasmid placed into bacterial cell

Engineered/altered bacteria multiply and produce new protein/product insulin/HGH

insulin used to treat diabetics and more people are developing diabetes so there is an increased need for insulin

Somatic Fusion (4)

Somatic fusion overcomes sexual incompatibility (in plants) OR used when 2 species cannot interbreed

Plant cells have their cell walls removed using cellulase

Resulting in protoplasts

Which are then fused to form a callus

Advantage of Genetic Engineering

Product/protein can be made quickly and easily

Don't need to use animals

Product won't be rejected by humans

[higherbiology-blog]

Genetics and Adaptation - Adaptations in Plants and Animals 1

OBTAINING FOOD - ANIMALS

Foraging Behaviour

This is the search for food involving patterns of movement called search pattens.

These

Increase the chance of finding food.

Vary with the availability of food.

Vary with the type of food.

Are species specific

Foraging Behaviour in Social Insects

The survival of colonies of social insects is dependent on food supply. If a forager finds a good food source it must share this to the rest of the colony.

Ants

There insects will wander about in search of food. If successful, they move 'straight' back to the nest leaving a chemical trail. The other ants will follow the trail and will exploit the food source. Re-marking of the trail will occur while the food lasts. 

Bees

If a foraging bee finds a good food source, on returning to the hive it will carry out a waggle dance. The orientation and length of this dance communicates the direction and distance to the food source.

Foraging Behaviour in Higher Animals

 Although instinct plays a great part in foraging behaviour, an element of learning is involved. There are many different strategies in foraging, some involving packs of animals (see cooperative hunting) and other individuals.

*Table to show different strategies used by individual hunters

Economics of Foraging Behaviour

The way animals get their energy can be looked at in terms of simple economics.

Selling price - Cost = Profit

In the case of foraging behaviour

Energy gained from food - Energy expended = Net energy gain or loss

Energy can be expended in

looking for food = search time

catching = pursuit time

preparing and eating = handling time

avoiding predators while foraging

If an animal operates at a loss for too long it will die. Ideally an animal will choose behaviour patterns which will maximise energy gain.

Choice of Behaviour Patterns

Food in limited supply If food is scarce then the animal is non selective in its choice of prey. This reduces the energy 'spent' on further search

Food plentiful Animals will choose prey that is easily caught. This reduces the energy 'spent' in further pursuits.

Handling of food difficult If food is plentiful and some foods are difficult to handle eg. some fruits may have different thicknesses of husk the animal may be selective and choose fruit that is easy to handle. 

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Control and Regulation - Enviromental Influences on Growth 2

THE EFFECT OF LIGHT

Plants

Absence of Light

Plants which are grown in the dark produce small, curled, yellow leaves and long, thin stems with long internodes.

This response to lack of light is called etiolation.

This reponse give the plant the best chance of reaching light by investing all its energy in increasing the length of the stem.

Photoperiodism

A plant responds to the length of daylight and darkness.

The light stimulus is detected in the leaves.

Flowering is an example of a photoperiodic response.

It is the length of darkness which is important in determining flowering.

Short Day Plants > Produce flowers when the number of hours of uninterupted darkness is equal to or greater than a critical length. > ie. the light period is shorter than a critical period. > Short day plants typically flower from late Autumn to early Spring.

Long Day Plants > Produce flowers when the number of hours of darkness is equal to or less than a critical length. > ie. the light period is longer than a critical length. > long day plants typically flower from late Spring to early Autumn.

Day Neutral Plants > Flowering in these plants is unaffected by the length of the dark period.

Animals

Breeding

Many birds and mammals are seasonal breeders.

Their gonads (testes/ovaries) become active only at certain times of the year.

Gonad development and sexual activity triggered by change in daylength.

Mating is timed to ensure that the young are born in Spring when there is adequate food.

Anials with a short gestation period (eg. birds and small mammals) will mate in early Spring.

This is triggered by increasing daylength.

Animals with a long gestation period (eg. deer) will mate in the Autumn.

This is triggered by decreasing daylength. 

[higherbiology-blog]

Control and Regulation - Enviromental Influences on Growth 1

EFFECTS OF CHEMICALS ON GROWTH

Plants

Plants require a variety of elements for healthy growth.

These chemicals are absorbed by plants from minerals in the soil.

Plants require four major elements (macro-elements) for healthy growth.

These macro-elements are nitrogen, phosphorus, potassium and magnesium.

These macro-elements have different functions in plants.

FUNCTIONS OF MACRO-ELEMENTS

Lack of any macro-elements results in specific deficiency symptoms.

The particular deficiency symptoms which result from the lack of a particular element can be investigated using water culture experiments.

WATER CULTURE EXPERIMENTS

The importance of each of the macro-elements to plant growth can be demonstrated by setting up a series of water culture experiments.

In these experiments, plants are grown in water containing all the macro-elements except the one being investigated.

The plants are compared against control plants grown in solutions containing all of the macro-elements.

A comparison of the plants grown in the two solutions shows the deficiency symptoms caused by he missing macro-elements.

The deficiency symptoms may indicate the function of the missing macro-element. eg. yellow leaves would suggest that the missing macro-element is involved in the synthesis of chlorophyll.

Experimental Set Up

The plants roots have a supply of mineral solution with missing macro-elements to compare with other solutions.

DEFICIENCY SYMPTOMS

ANIMALS

Iron > is a component of haemoglobin found in red blood cells. > haemoglobin carries oxygen. > shortage leads to anaemia

Calcium > is required to form calcium phosphate which is a component of bones and teeth. >in humans, calcium is also involved in blood clotting and muscle contraction.

Vitamin D > is essential for the absorption of calcium from the food in the intestine into the blood. > deficiency of vitamin D in children causes a bone disorder called rickets. > vitamin D can be formed in the skin by the action of UV rays from the sun.

Lead > inhibits the action of some enzymes eg. catalase > causes learning difficulties in young children > possible sources of lead include water pipes, paints and petrol. 

Drugs > many drugs taken during pregnancy can pass across the placenta and affect the development of the foetus. + Thalidomine - an anti morning sickness drug causes limb deformities. + Alcohol - may retard growth and mental development and cause foetal alcohol syndrome. + Nicotine - may retard growth and mental development. 

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Control and Regulation - Control of Growth 2

GROWTH IN ANIMALS

Growth in animals > takes place all over their bodies as there are no meristems in animals. > only takes place until adulthood is reached. 

Comparison of Plant and Animal Growth

REGENERATION IN ANGIOSPERMS

Regeneration is the process by which an organism replaces lost or damaged parts.

Flowering plants (angiosperms) have extensive powers of regeneration.

New shoots or roots can develop from pieces of plant tissue which contain meristematic cells (eg. apical meristem or cambium).

This allows new plants to be grown from stem or root cuttings.

REGENERATION IN MAMMALS

Mammals have only very limited powers of regeneration.

Regeneration is restricted to: > healing wounds > mending of broken bones > replacement of lost blood > renewal of damaged liver 

GROWTH PATTERNS IN PLANTS AND ANIMALS

Growth can be measured by an increase in > height or length > mass > dry mass

Growth patterns are often presented in the form of growth curves.

ANNUAL PLANT

A shows typical a S shaped growth curve.

 B shows initial loss of mass as food store in seed is used up during germination. C shows loss of mass due to seed dispersal.

DECIDUOUS TREE

  A shows continuous steady growth of the tree over many years.

B shows a loss of mass each autumn due to leaf fall.

HUMAN

A shows a period of rapid growth during the first few years (infant growth spurt). B shows another period of rapid growth during puberty (adolescent growth spurt).

C shows a slight loss of mass after birth

INSECT (eg. LOCUST)

A shows moulting (ie. loss of "skin") B shows period of rapid increase in length before new skin hardens.

C shows loss of mass due to the shedding of skin during moult.

[higherbiology-blog]

Control and Regulation - Control of Growth 1

GROWTH

Growth us an irreversible increase in the dry mass of an organism.

Growth usually involves an increase in the number of cells.

Drymass is a moe reliable indicator of growth than fresh mass because of fluctuations in water content of an organism.

PLANT GROWTH

In plants growth is restricted to meristems.

Meristems are regions where the cells are undifferentiated and are capable of division.

Primary Growth causes an increase in the length of a shoot or root.

Primary growth occurs at apical meristems which occur at the shoot and root tips.

GROWTH AT APICAL MERISTEMS

New cells are formed by mitosis and cell division at the apical meristem.

New cells then elongate and form a vacuole (vacuolation).

Differentiation of cells then occurs where the cells become altered and adapted to perform a specific function as part of the permanent tissues of the plant. eg. xylem vessels, phloem sieve tubes.

LATERAL MERISTEMS

Plants which live for more than one year must become thicker for additional support.

This secondary thickening is the result of the formation of new xylem tissue.

This new xylem develops each year is called secondary xylem.

This secondary xylem is produced by a lateral meristem called the cambium.

The cambium is found in the vascular bundles between the phloem and the xylem.

TRANSVERSE SECTION OF A STEM

Phloem transports sugars.

Xylem transports water and minerals.

ANNUAL RINGS

A complete ring of secondary xylem is formed each year by division of the cambrium.

Radial division of cambrium

  Cells divide to form a complete ring of cambrium

Tangential division of cambium

Cells divide to form a large amount of new xylem to the inside. This is known as secondary xylem. A small amount of secondary phloem is phormed on the outside.

The width of an annual ring is dependent upon the growing conditions present during that year.

Wider rings are produced by: > warm weather > wet weather

Narrower rings are produced by: > cold conditions > dry conditions > leaf loss

The xylem vessels former in the Spring are large to transpot the large quantities of water required as new leaves as formed.

As water flow is reduced in the Autumn, smaller xylem cells are formed