Organisms and Their Environment

Area of Study 1: Adaptations of Organisms

UNIT 2 BIOLOGY

WEEK 1: Learning OutcomesBy the end of the week, you should be

able to: Relate major features of organisms to survival

value – structural adaptations. Explain homeostasis and how it relates to

tolerance range of organisms. Explain nerve control in complex

multicellular organisms; including major sense organs and pathways of transmission of nerve impulses.

AdaptationsGenetically controlled features that may

assist survival and reproduction of organisms in their specific environment.

Structural features: particular aspects of the structure of an organism or any of its parts.

Physiological features: particular aspects of the function of an organism of any of its parts.

Behavioural features: activities that an animal performs in response to internal and external stimuli.

Name some examples of structural, physiological and behavioural

adaptations in any animal or plant you can think of

Structural Adaptations

Polar bear

Polar bearADAPTATION ADVANTAGE FOR SURVIVAL

Small ears To help reduce heat loss.

Thick greasy fur and a thick layer of body fat

To insulate from the cold and keep dry.

White fur For camouflage from prey.

Large feetTo spread body weight across snow. The wide paws act as good paddles and snow shoes.

Black skin To absorb any heat transmitted through the hair.

Body surface area is small compared to volume To reduce heat loss.

ARABIAN CAMEL

ADAPTATION ADVANTAGE FOR SURVIVALBrown fur Camouflage

Hump Fat storage. There is no other fat storage on the body.

Long thin legsMaximises distance from the hot sand and also increases heat loss because they have a large surface area compared with volume.

Wide feet To spread over the sand and prevent from sinking in.

Nostrils that can close To prevent sand entering.

Ears lined with fur To prevent sand and dust from getting in.Long eyelashes To protect the eyes from sand and dust.Little water in faeces and urine, and does not sweat easily

Less water lost from body.

KANGAROO RAT

Kangaroo RatADAPTATION ADVANTAGE FOR SURVIVAL

Brown fur For camouflage against predators

Nocturnal Only goes out at night when it is cooler

Doesn’t need to drink much water

Most of its water needs come from its diet of seeds

Does not sweat or pant To reduce water loss

Large back feet To escape from predators. It can move 2m in one bound

Long tail To help balance when hopping

A reminder: internal and external environmentsExternal environment:

Environment outside an organismCan vary greatly over short periods of timeHumidity, temperature etc.

Internal environment: The fluid surrounding living cellsMust be maintained within very narrow

ranges of pH, temperature, blood glucose, water, ions, urea, blood pressure.

What happens if...1. …….you drink a lot on a cold day?2. …….you work hard and sweat a lot on a warm

day, but you have not had a drink yet?3. …….you eat more salt than your body needs?4. …….you are too hot and your body

temperature starts to rise?5. …….you go out for a walk in the snow wearing

shorts and a tee-shirt?6. …….you eat a bag of lollies?

What happens if you drink a lot of water on a cold day?You do not sweat.You produce a large volume of dilute urine.

What happens if you work hard and sweat a lot on a warm day, but you have not had a drink yet?

There will not be enough water in your blood. The kidneys will release less water (more

concentrated urine). You will urinate less.

What happens if you eat more salt than you body needs?

Your kidneys put the excess salt into urine.

What happens if you are too hot and your body temperature starts to rise?

You will start to sweat. If you have pale skin you will notice it go red. You will change the way you behave to lose

heat: such as taking your coat off.

What happens if you go out for a walk in the snow wearing shorts and a tee shirt? You will start to shiver. If you have pale skin you will notice it go

paler. You will change the way you behave to

conserve heat: such as crossing your arms.

What happens if you eat a bag of lollies?

The glucose concentration of your blood rises.

Your pancreas will release the hormone insulin.

This hormone lowers your blood glucose level.

HomeostasisMaintenance of a relatively stable internal

environment within narrow limits.Any changes are dealt with by the body to

restore values to the normal state.

The hormone insulin is involved in the control of blood sugar.

The skin and blood vessels are involved in regulation of body temperature, as are behavioural mechanisms.

The kidneys and the amount you drink and sweat are involved in controlling water and ion levels.

Homeostasis overview

Structure of the Nervous System

Central nervous system (CNS) – brain, spinal cord and all the nerve cells.

Peripheral nervous system (PNS) – all nerve cells that lie outside of the CNS.

Activation of muscles and glands

‘Fight or flight’

Relaxation of muscles and glands

‘Rest and digest’

ReceptorsDetect specific sensory information from

the external environment (stimuli).They encode information about the

stimulus into electrical signals that are then carried by neurons to the brain.

The brain then stimulates effectors (such as muscles and glands) that carry out a response.

Photo-receptors (light)Light is focused on the retina.The retina contains two types of photo-

receptors called rods and cones, which contain light-sensitive pigments.

Fibres from the rods and cones lead to the optic nerve.

Cones: function in high light intensities, detect colour and detail, concentrated in the centre of the retina.

Rods: low light intensity, detect movement, no colour or detail, mostly around outside of retina.

Taste ReceptorsIn taste buds on the tongue.Each taste bud = 50 receptor cells.Detect chemicals that are dissolved in

saliva.The five basic tastes are sweet, sour, salt,

bitter and umami (‘pleasant savoury taste’ found in glutamates like MSG).

Taste buds occur all over the tongue, and can detect all five tastes.

Olfactory ReceptorsGive us the sense of smell.We smell something when vapours

consisting of lipid-soluble molecules bind to olfactory receptors in the nose.

Tasting food also involves the use of olfactory receptors.

Tactile ReceptorsTouch, pain, pressure, temperature.Distributed over the entire skin surface.Whiskers and bristles on the face of many

mammals have touch receptors at their base.

Sound ReceptorsConcentrated in the ear.They are tiny hair cells located on a

membrane in the cochlea in the inner ear.Sound waves in the form of vibrations are

passed through the outer ear, ear canal, eardrum, three bones (called the hammer, anvil and stirrup) and cochlea.

Which Receptor?

Turning upside-down on a roller

coasterAn insect crawling

over your handSitting on a pinWatching fireworksEating a bag of

salt and vinegar chips

Walking into a warm room

Someone shouting a warningCrossing the road

Listening to someone play the

guitar

Walking into a bakery

Chemical

Chemical

Pressure AND

Temperature

Light

Sound AND

Balance/position

Nerve Cells (Neurons)Neurones carry nervous impulses to and

from the CNS.There are three types of neuron:

Sensory (affector) neurons – carry impulses from sense organs to the CNS.

Motor (effector) neurons – carry impulses from the central nervous system (CNS) to muscles and glands and cause them to respond.

Connecting neurons – neither of the above; they make connections between other neurons. They are located in the CNS.

To CNS

A sensory neurone

To CNS

Connecting neurons

CytoplasmNucleus

Dendrites

A Coordinated ResponseWhen a person touches a hot object:

The stimulus is the hot temperature.There are temperature receptors in the

skin.They send a nervous impulse to the brain

which result in you feeling too hot.The effector is the bicep muscle which

results in you pulling you hand away from the hot plate.

The Reflex ArcA reflex arc is the nervous pathway for

reflex actions.A reflex arc happens when impulses cross

synapses to produce action.A synapse is the gap between two neurons.Electrical impulses cross the synapse

through the release of chemicals called neurotransmitters.

In the reflex arc, an impulse will bypass the conscious areas of your brain – so a reflex action is very fast.

Draw this diagram with labels

Spinal cord

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How the Reflex Arc Works1. The person touches a hot object.2. A temperature receptor in the skin is stimulated.3. The receptor sends impulses via the sensory

neurones.4. The sensory impulses travel in the nerve to the

spinal cord.5. In the centre of the spinal cord, the impulse is

passed across a synapse onto a motor neurone.6. The motor neurone conducts the impulse down

the fibre, back to the bicep muscle.7. This makes the muscle contract, and the arm is

pulled away.

Reflexes are automatic responses – they take no conscious thought.

Like the ‘knee-jerk’ reflex or change in pupil size.

STUFF TO DO!1. Test the knee-jerk reflex.2. Test pupil dilation and

contraction in response to changes in light intensity.

• Could you improve the time taken to react?

• What if you hit the joint harder?

Reflexes

Practical – How Fast Do Nerves Work?

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D i s t a n c e ( c m )

Conclusion

STUFF TO DO!Write a sentence

commenting on the accuracy of your measurements.

• Are they accurate?• If not, why?• How could you improve the accuracy?

Quiz

What is a change in the world

around you known as?

What is the name given to muscles or glands that respond

to impulses?

What is the name given to the cells

that pick up changes in your environment?

What is the special name given to the

nerve that carries the impulse from the

receptor to the brain or spinal cord?

What is the special name given to the

nerve that carries the impulse from the

brain or spinal cord to the effector?

Write the chain of events for the following scenario: ‘a silly year 11 boy has just thrown a pen towards a year 7 boys face. What does the year 7 boy do? Is it a reflex or does he have to think about doing it?’

What is the name given to the brain and spinal cord

together?