UNIT 2 BIOLOGY

1. UNIT 2 BIOLOGY Organisms and Their Environment Area of Study 1: Adaptations of Organisms

2. 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.

3. 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

4. Structural Adaptations

5. Polar bear

6. Polar bear

7. Arabian Camel

9. Kangaroo rat

10. Kangaroo Rat

11. 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.

12. 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?

13. 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.

14. 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.

15. What happens if you eat more salt than you body needs? • Your kidneys put the excess salt into urine.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. Activation of muscles and glands • ‘Fight or flight’ • Relaxation of muscles and glands • ‘Rest and digest’

23. 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.

24. 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.

27. 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.

29. 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.

31. 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.

33. 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.

35. 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

37. 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.

38. To CNS

39. A sensory neurone To CNS

40. Connecting neurons Cytoplasm Nucleus Dendrites

41. 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.

42. 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.

44. 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.

45. Draw this diagram with labels, on your own paper. relay neurone Spinal cord

48. 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?

49. Practical – How Fast Do Nerves Work?

50. 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.