Calderglen High School National 5 Biology Unit 2 ... · Calderglen High School National 5 Biology...

Multicellular Organisms

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Calderglen High School

National 5 Biology Unit 2



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Sub topic: Producing new cells Chromosomes are found in the nucleus of the cell and carry coded instructions called genes

from one generation of cell to the next. When most plant and animal cells divide, their nuclei

pass through the same series of changes, called mitosis.

A cell

Image BBC Bitesize Keeping the chromosome number correct Each species of plant and animal has a characteristic number of chromosomes in the nucleus of each of its body cells which is always the same for the specific species. For example, the body cells of human beings contain 46 chromosomes. Mitosis provides new cells for growth and repair of damaged cells and maintains the diploid

chromosome complement.

chromosomes

centromere

chromatid

A chromosome

nucleus


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Summary of the stages of mitosis

The diagram below represents stages in the process of mitosis in the correct sequence.

Chromosomes become

visible in the nucleus.

Chromosomes

shorten and appear

as chromatids joined

at the centromere

Two identical

daughter cells

have been

produced.

Nuclear membrane

disappears and the

chromosomes line

up along the

equator of the cell. Spindle fibres pull

chromatids to opposite

ends of the cell.

After a period of growth,

mitosis starts again each

cell


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Stem Cells

Stem cells in animals are unspecialised cells that are involved in growth and repair.

They are able to:

reproduce themselves by repeated mitosis while remaining unspecialised.

develop into various types of specialised cells when required e.g. red blood cell, nerve

cell or bone cell.

Possible uses of stem cells include the treatment of diabetes and cancer, repair to body organs

including bone and the windpipe or even the growth of organs for transplant such as liver and

skin.

Cell organisation

Specialisation of cells leads to the formation of a variety of cells, tissues and organs. Groups of

organs which work together form systems.

The cells are organised in the hierarchy as shown below

Cells Tissues Organs Systems Organisms Eg

muscle and bone.

Eg liver, eye or stomach

Eg circulatory system, digestive system

Liver

Bone

Nerve

Red blood cell

Image BBC

Bitesize


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Sub topic: Control and Communication

In a multicellular organism, cells communicate using nerve impulses or hormones.

Nervous control

The brain and spinal cord are made of neurons. The brain and the spinal cord make up the

central nervous system (CNS).

Many nerves join with the CNS. They bring messages as nerve impulses from sensory organs

which contain cells called receptors.

The CNS sorts this information and processes it.

To trigger a response, a different group of nerves are used to carry messages from the CNS to

effectors which are usually muscles.

image bbc bitesize


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The Brain

The brain plays a very important part in the way you respond to any factors that may affect

your body. Just to read this page, millions of nerve messages are zipping around within your

own brain.

The brain itself is made up of several different parts or regions, each with its own specialised

function.

image bbc bitesize

Part of the brain Function

Cerebrum Controls conscious actions, as well as

reasoning and learning.

Cerebellum Balance and muscle co-ordination

Medulla Controls the rate of breathing and

heartbeat.


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Neural pathways

This involves three types of neurons. Neurons are highly specialised because they carry

electrical impulses, they do not come in contact with one another:

A sensory neuron which carries electrical impulses from a sense organ to the CNS.

A relay neuron which is located in the brain or spinal cord. It receives electrical impulses

from the sensory neuron and transmits them to other neurons involved in the response.

A motor neuron which receives electrical impulses from relay neurons and transmits them to

a muscle or gland which will carry out the response.

When stimulated by an electrical impulse, muscles respond by contract and glands by

releasing chemicals. Muscle responds more rapidly than glands.

Reflex actions are fast responses that do not normally involve conscious thought. They

usually protect your body from harm. Examples of reflex actions include sneezing when

foreign particles enter the nose, withdrawal of a hand from a hot object, blinking when an

object moves near the eye.

The circuit of the neurons that act to produce the reflex action is called the reflex arc (refer

to the diagram on the next page)

Reflex arc

Sensory neuron Relay neuron

Motor neuron muscle

Burning candle

Image from BBC Bitesize


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The transmission of a nerve impulse through a reflex arc is called a reflex action. In the

example above the sensory neuron in the hand detects the heat and this initiates an

electrical impulse which travels towards the relay nerve. The impulse is transferred to the

rely nerve which passes on the impulse to the motor nerve. The nerve impulse travels along

the motor nerve to the muscle which brings about a muscle contraction and the hand is

withdrawn from the heat.

The neurons do not touch, there is a small gap called a synapse between neurons which

allows chemicals to transfer from one neuron to another.

Sensory neuron Relay neuron Motor neuron

Hormonal control

Hormones are made up of proteins. They are chemical messengers which pass on information to

target tissues which have special receptor cells sensitive to that specific hormone. Only some

tissues are affected by specific hormones. Glands which release hormones into the bloodstream

are known as endocrine glands.

Endocrine system

Synapse (gap

between neurons)

Synapse (gap

between neurons)

Pancreas

Ovary Testes

(male)



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Regulation of Blood Glucose Level in the Blood

Insulin produced when blood glucose level

is above the normal level

blood glucose level

Glycogen in the

liver

Glucagon is produced when the blood

glucose level falls below the normal level

Cells are constantly using up glucose present in

the bloodstream for energy.

A rise in blood glucose concentration is detected

by cells in the pancreas. These cells produce the

hormone insulin. This hormone is transported in

the blood to the liver where it activates glucose

to be converted to glycogen. This brings blood

glucose concentration down to around its normal

level.

If the blood glucose concentration drops a different set of cells in the

pancreas detect this change and release the hormone glucagon into the

bloodstream. This second hormone is transported to the liver and activates the

conversion of glycogen to glucose. The blood glucose concentration therefore

rises to its normal level.

Regulation of Blood Glucose levels

Scran image


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Sub topic: Reproduction

Diploid Cells

After fertilisation, a zygote (fertilised egg) is formed.

The cell is DIPLOID

A diploid cell has 2 sets of chromosomes (in humans this is 46 chromosomes).

One set has come from the male parent and one set has come from the female parent.

Every body cell has a copy of the chromosomes that was in the zygote.

Therefore, every body cell is a diploid cell.

The diploid number in humans is 46.

Haploid Cells

Eventually, the adult will produce sex cells.

Another name for the sex cells is GAMETE.

Gametes will only have one set of chromosomes.

A HAPLOID cell has only one set of chromosomes

The haploid number in humans is 23.

Fertilisation

Fertilisation is the fusion of the nuclei of the two haploid gametes to produce a diploid

zygote, which divides to form an embryo.

Fertilisation

produces a

diploid

zygote

Haploid

Gamete eg

sperm

Haploid

Gamete eg

egg


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Gamete Production in Animals

Like plants, animals produce gametes in sex organs.

In human males, SPERM are produced in the TESTES.

In human females, EGGS (ova) are produced in the OVARIES.

Millions of sperm cells are produced in the testes and are able to swim in fluid using their long tails.

Egg cells are the largest human cells because of the large food store in the cytoplasm.

Sperm (male gamete) Egg (female gamete)

head Cell membrane

Cytoplasm

containing a

food store

tail nucleus

Scran

images

http://www.scran.ac.uk/database/image.php?usi=000-000-623-653-R&cusi=000-000-623-653&searchdb=scran&


















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Animal Reproductive System

Male reproductive system image bbc bite size

Female reproductive system image bbc bitesize

Sexual Reproduction in Plants

Flowers are the organs of sexual reproduction in plants.

The flower contains both the male and female parts.

The ANTHER and FILAMENT together is known as the STAMEN. This is the male parts of the flower.

The male anther is the site of gamete production. The diploid anther cells produce the haploid pollen grains, which contain the male gametes.

The OVARY is the female part of the flower.

The female ovary is the site of gamete production. The diploid ovary cells produce haploid eggs (the female sex cell or gamete).

sperm duct

penis

Testes

testes

ovary

womb


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Sub topic: Variation and Inheritance

A characteristic shows DISCRETE VARIATION if it can be used to divide up the members of a species into two or more distinct groups.

Humans can be split up into two groups depending on their ability to roll their tongue and into four groups based on blood group types A, B, AB and O.

Data obtained from a survey of a characteristic that shows discrete variation is represented by a bar chart

Discrete variation

graph Image bbc

bitesize

Some characteristics are controlled by the alleles of a single gene – they are expressed as clear-cut PHENOTYPIC groups showing discrete variation.

In humans, the ability to roll the tongue is an example of the single gene inheritance.

In pea plants, the possession of lilac or white flowers is an example of single gene inheritance.


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Continuous Variation

A characteristic shows continuous variation when it varies amongst the members of a species in a smooth, continuous way from one extreme to another and does not fall into distinct groups.

CONTINUOUS VARIATION can be represented by a normal DISTRIBUTION CURVE (the curve would be bell shaped).

Image bbc bitesize

Few individuals show values close to the extremes of the range.

Most individuals show values close to the middle of the range (also known as the average).

Some characteristics are controlled by the alleles of several genes.

This results in the characteristic being expressed as a range of PHENOTYPES e.g. Human height.

A characteristic showing CONTINUOUS VARIATION controlled in this way by more than one gene is said to show polygenic inheritance.

Phenotypes and Dominant Genes

For every characteristic we have 2 genes – one from our mother and one from our father.

Genes are part of chromosomes.

Each characteristic is controlled by two forms of a gene.

Each parent contributes one form of the gene.

Each gamete (sex cell) carriers one of the two forms of the gene.

Differing forms of a gene are called ALLELES.

Example – The alleles for the gene for eye colour are blue, brown, green, etc.

PHENOTYPE – this is the physical appearance resulting from the inherited information.

Example – Someone with blue eyes has the phenotype blue eyes.

Genes or alleles can be said to be DOMINANT (shows up in the phenotype) or RECESSIVE (hidden when it is present along with the dominant gene).


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GENOTYPE – this is the combination of genes in a gene pair.

Genotype is represented by 2 letters (one letter for each gene).

If the 2 alleles that an organism possesses for a characteristic are identical, the organism is said to be HOMOZYGOUS for the characteristic.

BB has a phenotype black it is said to have a HOMOZYGOUS genotype.

Homozygous is often called ‘pure breed’ or ‘true breeding’.

Bb has the phenotype black but it is said to have a HETEROZYGOUS genotype.

If the 2 alleles that an organism possesses for a characteristic are different, the organism is said to be HETEROZYGOUS for that characteristic.

bb has the phenotype white and is said to be HOMOZYGOUS recessive.

Dominant

black gene Recessive

white gene

Note – the phenotype of this

individual is Black Hair


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Genetic Crosses

A genetic cross is laid out as follows:

A pea plant which produces round pea seeds is crossed with a pea plant which produces wrinkled pea seeds.

All the offspring are round. R: Round

r: Wrinkled

Parents Phenotype (P) Round X Wrinkled

Parents Genotype (P)

Gametes

First Generation (F1) Genotype

First Generation (F1) Phenotype

F1 X F1 =

Gametes

Genotype

Second Generation (F2)

Phenotype

Second Generation (F2)

F2 Phenotypic ratio 3 : 1

The actual ratio may differ from the expected ratio since fertilisation is a random process. An

element of chance is involved.

RR X rr

R X r

Rr

Round

Rr X Rr

R , r R , r

RR

Rr Rr rr

Round Round Round Wrinkled


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Sub topic: Transport systems in Plants

Plant organs are roots, stems and leaves.

Transport of water in plants

The root hair is an extension of the root cell and water is taken in by osmosis through the cells

selectively permeable membrane. When this cell has taken on a reasonable amount of water it

will have a higher water concentration than the next cell and so water will pass to this next cell

by osmosis. This process continues until the water reaches specialised water transport vessels

called xylem.

Root Hair Cell

Root

epidermal

cell

Xylem

vessel

Water travels across the root cortex cells by

osmosis and then enters the xylem vessels.

Image BBC Bitesize

Image – BBC Bitesize


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Xylem

Water movement in xylem vessels

Transpiration is the evaporation of water from the mesophyll cells in the leaves of plants. Water

evaporates through stomata whose opening and closing is controlled by guard cells, which are found

in the leaf epidermis (outer layer of cells). In order to replace this lost water, water is pulled up

through the xylem vessels. Mesophyll cells in the leaf require water for photosynthesis and this is

delivered via the xylem vessels.

Section of leaf

Water and minerals are transported from

the roots upwards to the leaves. Xylem

forms when the nucleus and end walls of

the cells disintegrate forming long hollow

lignified tubes. Xylem is a non-living

material.

Rings of lignin

(give plant

support)

Xylem

Mesophyll

cell in the

leaf

Air space in

leaf

Stoma Guard cell Lower

epidermis




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Factors affecting transpiration

The following factors affect the rate of transpiration; temperature, humidity, air movement and

light. These factors are known as abiotic factors.

Factor affecting

transpiration rate

Transpiration rate

Temperature

An increase in any of these factors will result in an

increase in the rate of transpiration Surface area of leaf

Wind speed

Humidity An increase humidity will result in decrease in

the rate of transpiration

Opening and closing of stomata

When the guard cells become turgid this forces the stoma open. When the guard cells are

flaccid the stoma closes.

Images – BBC Bitesize

guard

cells

stoma

epidermis

Stoma open Stoma closed


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Diagram of a leaf showing the position of the stoma.

Transport of sugar in plants

Sugar is transported up and down the plant in living phloem cells.

Differences between Xylem and phloem

Image -BBC Bitesize Sieve plate

Companion cell

Image BBC Bitesize

Sieve cell

Xylem Phloem Transports water and minerals Transports sugar

dead living

lignified Not lignified

No companion cell Companion cell

No sieve plates Sieve plates

stoma


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Sub topic: Transport Systems in Animals

Blood consist of two parts

White blood cells are part of the immune system and are involved in destroying pathogens

(disease causing micro organisms). There are two main types of cells involved:

Phagocytes carry out phagocytosis by engulfing pathogens

Lymphocytes which produce antibodies which destroy pathogens. Each antibody is

specific to a particular pathogen.

Red blood cells transport oxygen from the lungs to body cells. The pigment haemoglobin found

in the red cells reacts with oxygen at the lungs to form oxyhaemoglobin. At the tissues the

oxygen is released to diffuse into the cells.

Red blood cells have no nucleus In order to

maximise the space available to carry

oxygen. They are very small to fit through

the smallest blood vessels and have a

biconcave shape that increases their

surface area.

In mammals the main transport system is the circulatory system, comprising of the heart and

associated blood vessels. The heart is a muscular pump, pumping blood around the body to

deliver nutrients and oxygen as well as dispose of carbon dioxide and waste. The wall of the left

ventricle is thicker than that of the right because it has to pump blood all round the body.

Plasma

Other blood cells

Red blood cells

The role of blood

Blood consists of blood cells and the fluid

that surrounds them called plasma.

Many substances are transported

dissolved in plasma including glucose and

amino acids.

Red blood cells

Image source

SCRAN


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Structure of the heart


Right atrium

Left atrium

Right ventricle

Left ventricle

Valves between atria

and ventricles

Valve at exit to

pulmonary artery Valve at exit to

aorta

Valves in the heart and in veins prevent the backflow of blood


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Circulation

The Coronary artery

The first branch of the aorta

leaving the heart is the coronary

artery and this supplies the heart

muscle with oxygenated blood.

The diagram on the right also

shows how a build up of lipid

material called plaques can lead to

a coronary heart attack.


Pulmonary

artery

Pulmonary

vein

aorta

Vena cava

Deoxygenated blood Oxygenated blood

Coronary

artery

A heart


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Blood Vessels

Arteries carry blood away from the heart. They have a thick muscular wall and a narrow central

channel. The blood in arteries is under high pressure.

Veins carry blood towards the heart they have a thinner muscular wall than arteries and a wider

central channel. The blood in veins is under low pressure and they contain valves to prevent

backflow of blood.

Wide cental channel

Thick muscular wall

Thin central

channel

Artery

Thin muscular

wall narrow

central

channel

Valve Vein

Capillary

Capillary Capillaries are exchange vessels. Their

walls are only one cell thick to allow

materials to cross from tissues to

capillaries easily. There is a dense

network of capillaries giving a large

surface area. Examples of materials that

cross capillary walls are oxygen and

glucose into cells and carbon dioxide and

urea from cells to the capillary.


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Sub topic: Absorption of materials

Oxygen and nutrients from food must be absorbed into the bloodstream to be delivered to cells

for respiration. Waste materials such as carbon dioxide must be removed from cells into the

bloodstream to be removed from the body.

Tissues contain capillary networks to allow the exchange of materials at a cellular level.

Surfaces involved in the absorption of materials have certain features in common, these

include:

A large surface area

Thin walls

Extensive blood supply

All these features increase the efficiency of absorption.

Function of the lungs

At the lungs gas exchange takes place. Carbon dioxide diffuses from capillaries into the alveoli

and oxygen diffuses from the alveoli into the capillaries.

The Lungs

alveoli

airways inside the

lungs

lung


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An alveolus showing gas exchange Image from scran

Deoxygenated

blood

Oxygenated

blood

Air in

Air out

Alveolus and the large capillary network

deoxygenated blood oxygenated blood

CO2 O2

Red blood cell


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Feature of a gas exchange surface

Feature Function

large surface area to absorb oxygen

thin lining eases diffusion of oxygen into blood

surrounded by large capillary network

to pick up and transport oxygen

Digestive System

The small intestine’s internal surface is folded and has thousands of finger like projections

called villi. The large number of thin walled villi provides a large surface area. Each villus

contains a network of capillaries to absorb glucose and amino acids and a lacteal to absorb fatty

acids and glycerol.

Image BBC Bitesize

small intestine

Image from SCRAN






















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Structure of a villus

Image from

SCRAN

Thin wall of the villus

Lacteal –

Absorbs fatty acids and

glycerol

Image Scran

Blood capillary absorbs

glucose and amino

acids

Calderglen High School National 5 Biology Unit 2 ... · Calderglen High School National 5 Biology...

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Transcript of Calderglen High School National 5 Biology Unit 2 ... · Calderglen High School National 5 Biology...