Charleston Academy
Biology National 5
Unit 2: Multicellular Organisms
Revision: What you should know
(From Torrance (2013) National 5 Biology)
Key Areas 1-3
Cell Specialisation
Stem Cells and Meristems
Control and Communication
Word bank
1.
action
animal
arc
brain
cerebellum
cerebrum
chemicals
CNS
coordinated
cord
diabetes
division
electrical
endocrine
glucagon
glucose
glycogen
hormones
insulin
medulla
meristematic
motor
nervous
neurons
organs
pancreatic
plant
receptor
sensory
slower
specialised
stem
synapses
target
tissues
unspecialised
In a multicellular organism, groups of SPECIALISED cells are organised as
TISSUES, which are grouped together to form ORGANS.
2.
Stem cells are UNSPECIALISED cells involved in the growth and repair of a
multicellular ANIMAL. Division of STEM cells produces cells that have the
potential to become different types of specialised cell.
3.
Meristems are regions where cell DIVISION and growth take place in a
multicellular plant. MERISTEMATIC cells are non-specialised and are capable
of becoming any type of specialised PLANT cell.
4.
To survive, a multicellular animal needs the activities of all of its working
parts to be COORDINATED. The NERVOUS system provides the means by
which the necessary internal communication is achieved.
5.
In humans, the central nervous system (CNS) consists of the BRAIN and the
CORD.
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6.
The brain is made up of the CEREBRUM, which controls mental processes, the
CEREBELLUM, which controls muscular coordination and the MEDULLA, which
controls rate of breathing and heart beat.
7.
The nervous system is composed of nerve cells called NEURONS. A reflex
ARC is an arrangement of a sensory neuron, an inter (relay) neuron and a
MOTOR neuron along which an ELECTRICAL impulse passes from a RECEPTOR
to an effector. A reflex ACTION is a rapid, automatic response to a stimulus.
8.
SYNAPSES are gaps between neurons where CHEMICALS are released
allowing the transfer of an impulse from neuron to neuron.
9.
SENSORY neurons pass information to the CNS where it is processed. Motor
neurons transmit impulses to effectors enabling a rapid response to be made
by a muscle or a SLOWER response to be made by a gland.
10. Chemical messengers released directly into the bloodstream by ENDOCRINE
glands are called HORMONES. A hormone recognises its TARGET tissue by
the presence of specific receptors present on its cells.
11.
The concentration of glucose in the bloodstream is regulated by two
PANCREATIC hormones. Insulin promotes the conversion of glucose to
GLYCOGEN in the liver; GLUCAGON promotes the conversion of glycogen to
GLUCOSE as required.
12. DIABETES is a disorder caused by the person’s lack of ability to make
INSULIN or the failure of their body cells to respond to it.
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Key Areas 4 and 5
Reproduction
Variation and Inheritance
Word bank
1.
alleles
anthers
chromosome
continuous
counsellor
diploid
discrete
dominant
egg
fertilisation
genes
genotype
haploid
heterozygous
homozygous
more
numerous
ovaries
ovules
phenotype
pollen
polygenic
recessive
risk
smaller
sperm
testes
tree
uninterrupted
zygote
In a multi-cellular organism, the body cells are DIPLOID and the sex cells
(gametes) are HAPLOID.
2.
In male animals, the TESTES are the site of SPERM production; in females,
the OVARIES are the site of egg production.
3.
Sperm are SMALLER in size and more NUMEROUS than eggs.
4.
In flowering plants, the male gametes are contained in POLLEN produced in
ANTHERS. The female sex cells (EGG cells) are contained in OVULES
produced in the ovary.
5.
FERTILISATION is the process by which a haploid male gamete fuses with a
haploid female gamete to produce a diploid ZYGOTE.
6.
Variation exists amongst the members of a species. When a characteristic can
be used to divide the species into distinct groups, it is said to show
DISCRETE variation. When the characteristic varies in an UNINTERRUPTED
way from one extreme to the other, it is said to show CONTINUOUS
variation.
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7.
An
organism’s
physical
characteristics
are
known
collectively
as
its
PHENOTYPE.
8.
Each inherited characteristic is controlled by one or more units of heredity
called GENES. Each gene is part of a CHROMOSOME.
9.
Each gene normally has two or more different forms called ALLELES. An allele
that always shows its effects and masks the presence of the other form is
said to be DOMINANT. An allele that is masked by the dominant form is said
to be RECESSIVE.
10. The complete set of genes possessed by an organism is called its GENOTYPE.
The genotype of an organism with identical alleles of a gene is described as
HOMOZYGOUS; the genotype of an organism with two different alleles of a
gene is described as HETEROZYGOUS.
11.
A characteristic that shows continuous variation is controlled by alleles of
MORE than one gene and is said to show POLYGENIC inheritance.
12. A pattern of inheritance amongst the members of a family can be established
by constructing a family TREE. Analysis of a family tree relating to a genetic
disorder enables a genetic COUNSELLOR to help people to make decisions
about their parenthood based on assessment of RISK.
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Key Area 6 – The Need for Transport Systems (Plants)
Word bank
companion
1.
dead
epidermis
guard
hairs
lignin
mesophyll
phloem
sieve
stomata
sugar
surface
transpiration
transport
water
xylem
The body of a large multi-cellular organism has a small SURFACE area relative
to its size and needs one or more TRANSPORT systems to move essential
substances to all parts of its body efficiently.
2.
Plants need a transport system to carry WATER to the leaves for
photosynthesis and a second transport system to carry SUGAR from the
leaves to all other parts of plants.
3.
Water and mineral salts enter a plant by its root HAIRS. These materials are
transported up through the plant in XYLEM cells (vessels), which are
supported by LIGNIN and are DEAD.
4.
Some water arriving in the leaves is used by MESOPHYLL cells for
photosynthesis.
5.
Much of the water is lost as water vapour through tiny holes in the leaf
EPIDERMIS called STOMATA. The opening and closing of each stoma is
controlled by two GUARD cells. The loss of water by evaporation from leaves
is called TRANSPIRATION.
6.
The site of sugar transport in a plant is the PHLOEM tissue. It is alive and
composed of SIEVE tubes and COMPANION cells.
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Key Area 6 – The Need for Transport Systems (Animals)
Word bank
amino acids
alveoli
aorta
area
capillaries
carbon
cartilage
cava
cilia
coronary
dioxide
exchange
haemoglobin
heart
lacteal
low
mucus
oxygen
peristalsis
pressure
thick
ventricles
veins
villi
wider
1.
In mammals, the blood circulatory system transports nutrients, OXYGEN and
carbon DIOXIDE round the body.
2.
The HEART is a muscular pump made up of four chambers, the right and left
atria and right and left VENTRICLES.
3.
The vena CAVA carries blood from the body’s tissues and organs to the heart.
Blood is transported to the lungs in the PULMONARY arteries and back from
the lungs in the pulmonary VEINS.
4.
The AORTA caries blood from the heart to the body’s tissues and organs. The
first branch of the aorta is the CORONARY artery, which supplies the heart
wall itself with oxygenated blood.
5.
Arteries carry blood at high PRESSURE. They have THICK muscular walls and
a narrow central channel. Veins carry blood at LOW pressure and have thinner
walls and a WIDER central channel.
6.
CAPILLARIES are tiny, thin-walled vessels that present a large surface AREA
in tissues and organs, allowing materials to be exchanged.
7.
RED blood cells are specialised to carry oxygen. They contain the red pigment
HAEMOGLOBIN.
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pulmonary
8.
The body’s main airways are supported and kept open by rings of CARTILAGE.
Their lining secretes MUCUS to trap dirt and this is swept up and away from
the lungs by CILIA.
9.
The lungs contain many air-sacs called ALVEOLI. These are thin-walled and
present a large surface area in contact with blood capillaries, allowing
EXCHANGE of oxygen and CARBON dioxide to occur.
10. Food is moved through the digestive system by muscular activity called
PERISTALSIS.
11.
The wall of the small intestine bears tiny projections called VILLI, which are
thin-walled and present a large surface area for the absorption of digested
food. Each villus contains a blood capillary that absorbs glucose and AMINO
ACIDS and a LACTEAL that absorbs the end products of digestion.
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