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UNIT 2 BIOLOGY. Organisms and Their Environment Area of Study 1: Adaptations of Organisms. WEEK 1: Learning Outcomes. By the end of the week, you should be able to: Relate major features of organisms to survival value – structural adaptations .
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UNIT 2 BIOLOGY Organisms and Their Environment Area of Study 1: Adaptations of Organisms
WEEK 1: Learning Outcomes By 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.
Adaptations • Genetically 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
A reminder: internal and external environments • External environment: • Environment outside an organism • Can vary greatly over short periods of time • Humidity, temperature etc. • Internal environment: • The fluid surrounding living cells • Must be maintained within very narrow ranges of pH, temperature, blood glucose, water, ions, urea, blood pressure.
What happens if... • …….you drink a lot on a cold day? • …….you work hard and sweat a lot on a warm day, but you have not had a drink yet? • …….you eat more salt than your body needs? • …….you are too hot and your body temperature starts to rise? • …….you go out for a walk in the snow wearing shorts and a tee-shirt? • …….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.
Homeostasis • Maintenance of a relatively stable internal environment within narrow limits. • Any changes are dealt with by the body to restore values to the normal state.
Homeostasis overview • 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.
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’
Receptors • Detect 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 Receptors • In 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 Receptors • Give 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 Receptors • Touch, 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 Receptors • Concentrated 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? • Sound • AND • Balance/position • Chemical Eating a bag of salt and vinegar chips Turning upside-down on a roller coaster Listening to someone play the guitar Watching fireworks Walking into a bakery An insect crawling over your hand Sitting on a pin Walking into a warm room Someone shouting a warning • Light Crossing the road • Pressure • AND • Temperature • Chemical
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.
A sensory neurone To CNS
Connecting neurons Cytoplasm Nucleus Dendrites
A Coordinated Response • When 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 Arc • A reflex arc is the nervous pathway for reflex actions. • A reflex arc happens when impulses cross synapses to produce action. • A synapse isthe 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.
How the Reflex Arc Works • The person touches a hot object. • A temperature receptor in the skin is stimulated. • The receptor sends impulses via the sensory neurones. • The sensory impulses travel in the nerve to the spinal cord. • In the centre of the spinal cord, the impulse is passed across a synapse onto a motor neurone. • The motor neurone conducts the impulse down the fibre, back to the bicep muscle. • This makes the muscle contract, and the arm is pulled away.
Draw this diagram with labels, on your own paper. relay neurone Spinal cord
Reflexes • Reflexes are automatic responses – they take no conscious thought. • Like the ‘knee-jerk’ reflex or change in pupil size. • STUFF TO DO! • Test the knee-jerk reflex. • 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?
Conclusion • Are they accurate? • If not, why? • How could you improve the accuracy? • STUFF TO DO! • Write a sentence commenting on the accuracy of your measurements.
