Transcript Biology revision

B1 – Influences on life.
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How science works
• Independent variable – this is the quantity that you
change
• Dependent variable - this is what you measure
• Control variable – this is what must be kept the
same to ensure a fair test
• Hypothesis – an idea based on observations without
experimental evidence
• Secondary evidence - data collected by someone
else, you may find it in a book or on the internet
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2
How do scientist validate results?
1. they repeat experiment results
2. they publish their findings in scientific journals
3. conference presentation
4. peer review/other scientists investigate the
same findings.
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3
Kingdom characteristics
They are unicellular, with a nucleus. e.g. amoeba
and euglena - protoctists
They are unicellular, with no nucleus e.g.
bacteria – prokaryotes
they are multicellular, saprophytic feeders, e.g.
moulds, mushrooms, yeast - fungi
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They are multicellular and autotrophic feeders plants
They are multicellular, heterotrophic feeders,
e.g. fish, amphibia, reptiles, birds and mammals
- animals
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Kingdom to species
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Kingdom
Phylum
Class
Order
Family
Genus
Species
HUMANS
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo
Sapiens
LIONS
Animalia
Chordata
Mammalia
Carnivora
Felidae
Panthera
Leo
Kings Prawn Curry Or Fat Greasy Sausages
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What is binomial classification?
• Binomial classification is a system for naming
plants and animals by two Latin names: the first
indicating the genus and the second the species
to which the organism belongs e.g.
Homo Sapiens
genus
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species
Panthera Leo
genus
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species
How do scientists classify vertebrates?
• The vertebrates are animals with a backbone.
Scientist classify them according to:
1. how the animal takes in oxygen – lungs, gills or
through the skin
2. thermoregulation – maintains own temperature
(homeotherms) or temperature varies with
surroundings (poikilotherms)
3. reproduction – internal or external fertilisation,
lay eggs (oviparous) or give birth to live young
(viviparous).
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Vertebrates
have gills, external fertilisation,
oviparous, poikilotherm - fish
some have lungs or gills, external
fertilisation, oviparous, poikilotherm –
amphibian
have lungs, internal fertilisation,
oviparous, poikilotherm - reptiles
have lungs, internal fertilisation,
oviparous, homeotherm - birds
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have lungs, internal fertilisation,
vivaparous, homeotherm - mammals
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Why is it difficult to classify sharks?
• Sharks are fish but give birth to live young and
use internal fertilisation like mammals.
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Why are whales classified as mammals?
• Whales breathe surface air (no gills, they just
hold their breath for a really long time),
• They give birth to their young ,
• They are homeotherms (maintain their own
body temperature).
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What is a species?
• Species is a group of organisms that can
reproduce/interbreed with each other to
produce a fertile offspring.
• Hybrid is an organism that is the result of
breeding together two different species, e.g.
zedonk (zebra & donkey), liger (lion & tiger)
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Why classification is complicated ?
1. variation within a species
2. hybridisation (closely related species breed to
produce offspring that have characteristics of
both – the hybrids are often infertile)
3. ring species – neighbouring populations of
species may have slightly different
characteristics but can still interbreed as part of
a chain but the two ends of the chain can’t
interbreed.
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Why is it difficult to classify virus?
1. It does not show all seven processes for life
i.e. reproduction and movement
2. It can only reproduce inside the host cell
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Why is it difficult to classify euglena?
• Because euglena has –
1. chloroplasts, like a plant
2. no cell wall, like an
animal
3. a flagellum to swim with,
like some bacteria.
• A fifth kingdom, called
the protoctista, was made
for organisms like
euglena
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Variation
• Continuous variation
- characteristic that
changes gradually
over a range of values
shows continuous
variation, e.g. height,
weight
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Disontinuous variation
- characteristic with only
a limited number of
possible values, e.g.
gender (male or female)
blood group (A, B, AB or
O) and eye colour.
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Charles Darwin theory of evolution
• How do species adapt and change?
1. variation – in any population of organisms there
will be some differences
2. over-production – many organisms produce more
offspring than necessary
3. struggle for existence – there is competition for
survival and resources between the organisms
4. survival - those with helpful characteristics are
more likely to survive to breed
5. useful characteristics inherited by the offspring
6. gradual change of the species over a period of time
as useful characteristics are passed to offspring.
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Charles Darwin theory of evolution
• The theory is supported by evidence from
1. fossils
2. rapid changes that can be seen to occur in
microorganisms such as antibiotic-resistant
bacteria – MRSA
3. DNA - scientists can now examine the DNA
from different species of organism and use the
data produced to see how closely related the
two species are to each other.
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Genes and inheritance
• The cell’s nucleus
• Alleles are different
contains chromosomes
forms of a gene.
made from long DNA
• Alleles can be
molecules.
dominant or recessive.
• A gene is a short
section of DNA.
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Genetic diagrams
• The alleles in the organism are the genotype.
What the organism looks like, e.g. red flower is
the phenotype.
• Offspring with two alleles the same are
homozygous e.g FF or ff.
• If the alleles are different e.g Ff then it is
heterozygous.
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Genetic diagrams
• F = red flower (dominant), f = white flower(recessive)
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Punnett Squares
Ff
parental genotype:
possible gametes:
possible combination
of allele in offspring
x
F or f
Ff
F or f
F
f
F
FF
Ff
f
Ff
ff
probability of getting white flower 1 in 4
percentage of getting white flower 25% chance
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Cystic fibrosis
• Cystic fibrosis (CF) is caused by two
copies of recessive allele.
• People with CF produce abnormally thick and
sticky mucus in their lungs and airways.
• As a result, they are more likely to get
respiratory infections.
• Daily physiotherapy helps to relieve congestion,
while antibiotics can fight infection.
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Sickle cell disease
• Sickle cell disease is a caused by two copies
recessive genes.
• The red blood cells of sufferers are misshapen
and can stick together which can block blood
vessels.
• Sickle cell disease sufferers can become very
tired and quickly get out of breath.
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Blood glucose control
• Homeostasis is maintaining constant internal environment
i.e. blood glucose, core body temperature and water
Glucose rises
(eat food)
Normal blood
glucose level.
Glucose falls
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(exercise)
Insulin produced by the
pancreas causes ______to
glucose
_______
change to glycogen
______ and
stored in the liver.
Negative
feedback
Normal blood
glucose level.
glucagon
_______ released by
pancreas. Glucagon convert
glycogen from the liver
______
back to glucose
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Thermoregulation – negative feedback
• The hypothalamus controls core body
temperature
HOT
hairs lowered
sweating
vasodilatation
COLD
hairs raised
no sweating
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vasoconstriction
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Hormones
• Hormones are chemicals secreted by glands in
the body.
• Blood transports hormones from the glands to
the target organs.
Gland
ovary
ovary
pancreas
Hormone
oestrogen
progesterone
insulin
testes
testosterone
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Target organs
ovaries, uterus
uterus
liver
male reproductive
organs
Plant hormones
• Auxin is a plant hormone produced in the stem
tips and roots, which controls the direction of
growth
• Plant hormones are used in
1. selective weedkillers - kill some plants but
not others.
2. rooting powder - makes stem cuttings quickly
develop roots.
3. control fruit ripening - some hormones slow
the ripening of fruits and others speed it up.
4. seedless fruits – some seedless fruits are
produced using plant hormones
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Tropisms
• A 'tropism' is a growth in response to a stimulus.
Response
Part of
plant
Direction of
growth
to get maximum
light for
photosynthesis
less chance of
drying out
stem tip
negative
root tip
phototropism
positive
geotropism
negative
stem tip
geotropism
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Advantage
towards
gravity
away from
gravity
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more chance of
finding light
Tropism
Phototropism
Geotropism
- causes elongation of the tip of
the plant on the side of the
shoot furthest from the light
- tip is bent towards the
light/the plant grows in the
direction of the light gives
maximum light for
photosynthesis
- carbohydrate/starch produced
during photosynthesis with
provides energy for growth and
metabolism.
- causes roots to grow towards
gravity into the soil
- the plant get anchored to the
ground hence maximises
1. water uptake
2. mineral uptake
minerals and water are
important for photosynthesis.
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The nervous system
• The nervous system allows the body to respond,
through effectors (e.g. muscle contracting to
move the arm) to changes in the environment
detected by receptors (e.g. ear, eye and skin)
touch, pressure,
pain
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chemical in food
chemical in the air sound and position
of the head
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Neurones
• Neurones carry information as tiny electrical
signals, there are three types of neurones
1. sensory neurones carry signals from receptors to
the spinal cord and brain.
2. relay neurones carry messages from one part of
the CNS to another.
3. motor neurones carry signals from the CNS to
effectors.
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Typical Neurones
• The axon is surrounded by a fatty layer known as the
myelin sheath
• This helps to insulate and speeds up signals in the
axon.
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Synapses
• Where two neurones meet
1. An electrical impulse travels
along an axon.
2. neuron releases chemical
messengers called
neurotransmitters.
3. These chemicals diffuse across
the synapse (the gap)
4. The receptor molecules on the
second neuron bind only to the
specific chemicals released from
the first neuron. This stimulates
the second neuron to transmit
the electrical impulse
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Reflex actions
1. receptor detects a stimulus - change in the
environment
2. sensory neurone sends signal to relay neurone
3. motor neurone sends signal to effector
4. effector produces a response
2
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1
4
Groups of drugs
• Drugs can affect nerves impulses, reaction times
and behaviour.
1. Stimulants e.g. tea and coffee. They increase the
transmission of signals from one nerve cell to the
next, which then increases alertness, heart rate
and breathing rate.
2. Sedatives e.g. alcohol slow down the nervous
system and reactions.
3. Hallucinogens e.g. LSD changes our response to
what we see, feel and hear.
4. Painkillers e.g. paracetamol and morphine. They
block nerve impulses from the painful part of the
body, or block nerve impulses travelling to the
part of the brain responsible for perceiving pain.
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Groups of drugs
• Why is it difficult to give up cigarettes?
• Cigarettes contains nicotine which is addictive
• It is difficult to give up because the body needs
a constant 'top-up' to maintain the effect as the
receptor sites in the brain become more used to
the nicotine
• smoking more means an increased exposure to
tar, which is a carcinogen (chemicals cause
cancer).
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Transmission of pathogens
1. Direct contact i.e. kissing(cold sore),
touching(chicken pox) and sexual intercourse(HIV,
gonorrhoea)
I. Vertical transmission - when pathogens pass
from a mother to her unborn baby through the
placenta, e.g. measles, HIV.
II. Horizontal transmission - when pathogens pass
from one person to another by touching, kissing
or sexual intercourse.
2. Indirect contact i.e. droplets in air(TB, flu, cold),
water (cholera), food(salmonella, food poisoning)
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Body defences
Physical barriers
1. skin - protecting
against microbe infection
and dehydration.
2. nasal hairs, mucus and
cilia - Nasal hairs keep
out dust and larger
microbes.
- Sticky mucus traps dust
and microbes, which are
then carried away by cilia
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Chemical barriers
1. hydrochloric acid in
stomach kills microbes.
2. tears, saliva and
mucus - contain an
enzyme called lysozyme
which destroys microbes.
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How do plant defend themselves?
• Plants produce antibacterial chemicals that kill
microbes by breaking their cell wall.
Mint - has chemicals that kill
bacteria. It is used in toothpaste
because of its fresh taste.
Witch hazel can be used to prevent
an infection getting in through the
skin.
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Antibiotic resistance
1. Mutations occur in the genes of individual
bacterial cells
2. Some mutations protect the bacterial cell from
the effects of the antibiotic.
3. Bacteria without the mutation die or cannot
reproduce with the antibiotic present
4. The resistant bacteria are able to reproduce
with less competition from normal bacterial
strains.
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Interdependence
• Food chains show the feeding relationships in a
habitat. Food chains always start with
producers.
oak tree → caterpillar → blue tit → sparrowhawk
• Pyramids of biomass are
charts that show the mass of
living organisms at each step in
a food chain.
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Pyramid Of Numbers And Biomass
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Interdependence
• Consumers eat plants or animals, or both.
• A food chain can be used to rank different types of
consumers
seaweed
limpet
producer
primary
consumer
crayfish
secondary
consumer
human
tertiary
consumer
• producers – make their own food;
• primary consumers – eat producers;
• secondary consumers – eat primary consumers;
• tertiary consumers – eat secondary consumers.
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Parasitism
• Parasitism - relationship between two species
of plants or animals in which one benefits at the
expense of the other, e.g.
tapeworms live in gut to absorb
food
mistletoe - their roots absorb
nutrients and minerals from host
tree.
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How are tapeworms adapted?
1. Hooks and suckes – to attach it to the
intestine
2. Flat body – large surface area for food
absorption
3. Each segment has male and female
reproductive organs – so it can fertilise its
eggs if others are not nearby
4. Surface contain substance – protect it from
digestive enzymes.
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Mutualism
• Mutualism relationship between organisms of
two different species in which each is benefited,
e.g.
Bees eat nectar from flower and
spread pollen.
The rhinoceros' relief of its ticks
and the birds feed
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The bird gets a meal and the
crocodile gets a valuable tooth
cleaning: they both benefit
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Air pollution
• The most common source of air pollution is the
combustion of fossil fuels.
Pollutant
Typical effect
deposits soot on buildings and
trees, causing them damage.
smoke
Permeates the air, making it
difficult for living creatures to
breathe.
carbon monoxide poisonous gas
greenhouse gas that contributes to
carbon dioxide
global warming
sulfur dioxide
contributes to acid rain
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Indicators of air pollution
• Lichens are natural indicators of air pollution.
• Air pollutants (sulfur dioxide) dissolved in
rainwater damage lichens and prevent them
from growing.
• In places where no lichens are growing, it's
often a sign that the air is heavily polluted with
sulfur dioxide.
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Indicators of water pollution
• Nitrate fertilisers, pesticides(used by farmers to
kill weeds) may be washed or blown into rivers.
Sulfur dioxide in the air can dissolve in water to
form an acidic solution
fresh water shrimp indicator clean
water
Bloodworm indicate polluted water
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Eutrophication
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The Carbon Cycle
1 combustion
Decomposers
2 respiration
e.g. bacteria
waste
material
Carbon dioxide
in air
3 respiration
7 death
Fossil
fuel
6 feeding
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Plants
4 photosynthesis
5 respiration
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The Nitrogen Cycle
death &
excretion
feeding
proteins &
nitrogen fixing
urea
by root nodule
bacteria
nitrogen gas
decomposers
in the air
, bacteria in
lightning &
soil
breakdown by
nitrogen fixing
denitrifying
by soil bacteria
ammonia
bacteria
absorption
by the roots
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nitrates in
the soil
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oxidation by
nitrifying bacteria
Revision tips
• Make your own revision cards
• Learn ALL keywords, make use you understand
them
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