National 5 Biology Unit 2 Multi-cellular Organisms

Transcription

1 National 5 Biology Unit 2 Multi-cellular Organisms 1

2 Cells, tissues and organs Learning Intentions Cells Tissues Organs Systems Organism I can explain what is meant by the term specialisation of cells in animals and plants. I can give details of how the structure of an animal cell or plant cell can relate to its function. I can state that the cells in organs are specialised for a specific function. I can describe the levels of organisation found in animals and plants. Specialised cells Plants and animals are multi-cellular organisms as they have more than one type of cell. Each type of cell is designed to carry out a particular job or function. This is known as cell specialisation. Examples Sperm Cell Root Hair Cell Red Blood Cell Tissue Cell type Function Cells of one type group together in the body to form tissues. For example, muscle tissue is made up of only muscle cells. 2

3 Organs are made up of different tissues working together to carry out a specific job. An organ can contain different types of tissue. For example, the heart is made up of muscle tissue, blood tissue and nervous tissue (nerves). Each tissue is made up of specialised cells that allow each tissue and subsequently each organ to carry out a specialised job. Organ systems are made up of two or more organs that work together to provide a common function e.g. Nervous system, circulatory system, reproductive system etc. Stem Cells and Meristems Learning Intentions I can state that stem cells have the ability to divide to produce cells that can become different types of cells. I can state that stem cells are involved in growth and repair. I can describe the role of meristems in plants. I can state that non-specialised cells can become any type of plants cell and they contribute to growth. Stem cells Stem cells are unspecialised cells that have the potential to divide and make more stem cells by mitosis or to become another type of cell with specialised function. In early development embryos are composed of stem cells. This allows the embryo to develop all the different parts of the body and the different cell types needed to form a fully functional body. Through embryonic and foetal development the number of stem cells steadily decreases until very few stem cells remain. Production of blood cells. Blood contains red and white blood cells that are repeatedly replaced by new blood cells produced by stem cells. These stem cells are found in red bone marrow- found inside bones. Uses of stem cells in medicine Stem cells can be cultured (grown) in laboratories. These cells have huge medical potential, as they can become any type of specialised cell. 3

4 Research scientists hope to develop methods that could use stem cells to replace diseased or worn out parts of tissue with new, healthy tissue. For example, repairing damaged heart tissue; treat diabetes; or to reverse Parkinson s disease and Alzheimer s disease. Embryonic stem cells Vs. Adult stem cells Stem cells have been used in medicine for many years bone marrow transplantation is a form of stem cell therapy using adult stem cells. However, adult stem cells can only form a limited range of specialised cells. Embryonic stem cells can have the potential to make any body cell. Ethical Issues Objections Human life should never be created as a means to an end. Catholic Church hold the belief that new life begins at the moment of conception and embryos should have full human rights. Use of embryonic stem cells is not justified when other sources of stem cells are available Researchers argue that it is still not clear which types of stem cells will prove the best therapeutically. A balance has to be found between the rights of the embryo against the potentially large benefits that others may gain from research and ultimately stem cell based treatments. Meristems In animals, growth can occur all over the body. In plants, growth is restricted to special points call meristems. These regions contain stem cells. The cells at a meristem are constantly dividing by mitosis to form more meristemic cells or cells which can elongate and develop into specialised cells and tissues in the plant. Meristemic cells have the potential to become any type of cell in the plant. These are found at the root and shoot tips. They cause an increase in the height of the plant and length of the roots. 4

5 Control and Communication Learning Intentions I can describe the structure of the brain. I can give details of the functions of the different structures of the brain. I can describe the structure and function of the central nervous system (CNS). I can state that the CNS is the communication system. I can describe the role of sensory and motor neurons. I can explain the role of sensory, relay and motor neurons in a reflex arc. I can state that electrical impulses move along neurons. I can explain the importance of synapses in the nervous system. I can describe the different responses brought about by the CNS. I can explain what a reflex action is and give some examples. I can explain the importance of reflex actions. I can state the function of endocrine glands. I can describe the role of hormones in signalling. I can describe the role of the liver, pancreas, insulin and glucagons in controlling blood glucose levels. I can state that glucose can be stored as glycogen in the liver. I can describe the causes and treatment of type 1 and type 2 diabetes. I can explain the importance of controlling blood glucose levels. The Brain The brain is the most complex organ in your body. It is protected by the skull and controls the vital processes that occur in your body, keeping you alive. 5

6 To remember the difference between the location and functions of the cerebrum and cerebellum, cerebellum = balance cerebrum = reasoning The Nervous System. In humans, the nervous system is composed of the brain, spinal cord and nerves. The central nervous system (CNS) is made up of the brain and spinal cord. The central nervous system sorts information from the senses and sends messages to muscles and other parts of the body to stimulate the appropriate response. Neurones are specialized cells of the nervous system that conduct electrical impulses through the body, to and from the CNS. A neuron consists of a cell body attached to nerve fibres. An electrical impulse is carried towards the cell body of a neuron by a sensory fibre and away from it by an axon fibre. The fatty myelin sheath acts as insulation and speeds up the impulse. Reflex Arc Sense organs contain receptor cells which detect stimuli (changes in the conditions). This information is passed along sensory neurones to the CNS. The CNS processes the information and brings about the responses. Responses are 6

7 Sensory fib passed from the relay neuron then along motor neurons to the effectors. An effector may be a muscle that brings about a rapid response. Stimulus receptor sensory neuron relay neuron motor neuron effector response Synapse A tiny space called a synapse occurs between the axon ending of one neuron and the sensory fibre of the next. When a nerve impulse arrives, the ending of the axon branch releases a chemical. This diffuses across the space between the two neurons and triggers off an impulse in the sensory fibre of the next neuron. Reflex actions The transmission of a nerve impulse through a reflex arc results in a reflex action. This is a rapid, automatic, involuntary response to a stimulus. When the flame (stimulus) comes in contact with the hand, the pain receptors send an electrical impulse up the sensory neuron, through the relay neuron in the spinal cord, to the motor neuron to the arm muscle (effector) to move the arm away from the harm (response) and drop the burning match. Reflex actions protect the body from damage. Some examples of reflex actions in humans include blinking, knee jerk, dilation/constriction of pupil of eye. 7

8 Hormonal Control of the body As well as using the nervous system to control and coordinate the body, hormones play a similar role in keeping your body working. Hormones are chemical messengers (made of protein) which are made by the endocrine glands in the body and travel in the blood to specific target tissues. When the hormone arrives at its target tissue the specific receptors in the tissue detect the hormone and initiating a response. Make a list of hormones and functions: Glands of the endocrine system Osmoregulation in the human body It is important to regulate blood water concentration so that cells have the right water concentration. Monitoring centre Hypothalamus (osmoreceptors) Control Centre Pituitary gland Hormonal message ADH Effector tissue Kidney Homeostatic control of blood water concentration 8

9 Blood Glucose Regulation All living cells in the human body need a continuous supply of energy. Most of the energy required by cells is gained through the breakdown of glucose during aerobic respiration. Glucose concentrations in the blood must be kept within tolerable limits and involves the following: Monitoring centre Receptor cells in Pancreas Control Centre Pancreas Hormonal message Insulin or Glucagon Effector tissue Liver Insulin causes the liver to convert glucose glycogen (a storage carbohydrate) and therefore reduces the levels of glucose in the blood. Glucagon causes the liver to convert the storage carbohydrate glycogen glucose and therefore increases the levels of glucose in the blood. The system described above is an example of negative feedback since the corrective mechanism opposes the existing trend and then switches off when blood glucose levels return to normal. 9

10 During an emergency the adrenal gland secretes the hormone adrenaline into the bloodstream Adrenaline overrides the normal homeostatic mechanism by inhibiting the secretion of insulin and promoting the breakdown of glycogen to glucose. This raises the levels of glucose and allows the body to produce energy for flight or fight. Once the emergency is over the levels of adrenaline drop and allow normal homeostatic control mechanisms to take over. Diabetes People who suffer from diabetes are unable to control their blood glucose levels. Diabetes is the result of a communication pathway that has broken down. Write notes on diabetes cause, symptoms, treatment. Reproduction Learning Intentions I can describe the chromosome complement of gametes. I can describe the structure if the male and female sex cells and state where they are produced. I can give details of the male and female reproductive structures, including their function. I can describe the process of fertilisation in animals. I can give details of the chromosome complement of a gamete and zygotes in animals. I can name the sex cells found in plants and state where they are produced. I can describe the reproductive structures found in plants and give their functions. I can describe the process of fertilisation in plants. 10

11 I can give details of the chromosome complement of a gamete and zygotes in plants. Sexual reproduction Reproduction must take place in all species to produce offspring and maintain population numbers. Sexual reproduction in animals involves two parents. Animal Reproduction Gamete production Gamete Sperm Number produced Relative Size Important structures and functions Diagram Egg (ova) In each diagram below highlight the site of gamete production (the gonads). Male reproductive system Female reproductive system 11

12 Structure Male Testes Function Penis Urethra Sperm duct Female Ovary Oviduct(fallopian tube) Uterus Vagina Cervix Fertilisation Every month the female will release an egg from the ovary (Ovulation). Cilia beat the egg down the oviducts towards the uterus. If sexual intercourse has taken place and sperm have been deposited into the female s vagina they will swim up the uterus and into the oviducts. It is here in an oviduct that fertilisation takes place. Stages of development Egg + Sperm Zygote Embryo Foetus Baby 12

13 Plant reproduction Flowers are the organ in which sexual reproduction takes place in plants. Highlight in the diagram where gamete formation occurs. Structure Sepal Petal Anther Pollen Stigma Ovary Ovule Nectary Function Protects unopened flower Brightly coloured to attract insects Produces pollen Contains male nucleus Where pollen lands Contains ovule Contains female nucleus Produces nectar to attract insects Nectar is sugary water Gametes in flowering plants Male-Pollen grains Female ovule in the ovary Pollination This is the process of transferring pollen grains (male) from the anther to the stigma of the flower. This can by wind of insect transfer. Growth of a pollen tube Step 1- The pollen grain has landed on the sticky sugary stigma which initiates the pollen tube to grow. Step 2- The pollen tube grows down the style, into the ovary and into the ovule. Step 3- The male nucleus will travel down the pollen tube to meet with the ovule nucleus where fertilisation will take place. Fertilisation This is the process when the nucleus of the pollen grain (haploid) fuses with the nucleus of an ovule (haploid) to produce the zygote (diploid) which will become the seed. 13

14 The ovary will grow into a fruit containing the seed and after dispersal the seed will grow into a new plant. Variation and Inheritance Learning Intentions To develop knowledge on inheritance To be able to describe and explain the difference between continuous and discrete variation. To know the biological terms of genetics and inheritance. Such as phenotype, dominant, recessive and true breeding and identify examples from given crosses To be able to use a punnet square to carry out a Monohybrid cross. To develop knowledge on polygenic inheritance. To develop understanding on family trees and the benefits they have. Fertilisation is the fusion of the two haploid nuclei of the gametes to form a diploid zygote. Fertilisation is a random process. The zygote ends up with half its genetic complement from each parent. This is how characteristics are passed down through generations. THIS IS CALLED INHERITANCE. Variation There are two types of characteristics that are inherited from parents; 1) Discrete Variation - Characteristics with distinct categories e.g. blood group, eye colour, ability/inability to roll tongue 2) Continuous Variation - A characteristic which increases or decreases in a regular way and can be measured e.g. height, hand span, shoesize Continuous variation can also be described as Polygenic. 14

15 The following terminology is used to describe inheritance. Gametes Genotype Phenotype Alleles Dominant True breeding Heterozygous Polygenic Monohybrid Cross True Breeding Example There is a standard way to set out a genetic cross, as shown below. 15

16 Observed vs Predicted Ratios Punnet squares give a predicted ratio. We predict a ratio of 3:1, for the above cross between two true breeding (homozygous) mice however we rarely get this in practise. This is because fertilisation is random and involves the element of chance. Family tree A family tree is a diagram showing the relationships between people in several generations of a family. Family trees can be used to identify individuals with a genetic condition. A genetic condition is an illness or condition caused by abnormalities in genes or chromosomes e.g. Down s syndrome, haemophilia, cystic fibrosis. Genetic counselling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning. 16

17 Transport Systems Plant Transport Systems Learning Intentions To understand why multi-cellular organisms need transport systems. To understand the function of a leaf in transport systems of a plant To know the structures involved in transport of water and food around a plant To understand the functions of transpiration in a plant To describe the process of transpiration To state the effects of environmental conditions on transpiration and how to measure this effect The need for transport mechanisms in multi-cellular organisms Single celled organisms do not need transport systems. They are so small that substances can move in and out of them by diffusion. Multi-cellular organisms with several or many layers of cells and which are more active need specialised exchange and transport systems. Diffusion would take place too slowly to supply the organism with what it needs. Leaves Photosynthesis occurs in the leaves of green plants. 17

18 Functions of the Parts of a Leaf Structure Feature Function Cuticle Waxy layer Epidermis Close fitting cells Mesophyll Contain many chloroplasts Vein Guard cell Tubes made from xylem and Phloem Changes shape Stoma Pore 18

19 Structure of Stoma guard cell chloroplast thick inner part of cell wall Closed stoma pore thin outer part of cell wall Open Stomatal Movements Stomatal opening and closing is dependent on changes in turgor in the guard cells caused by entry or exit of water. Stomatal opening When water enters a pair of guard cells they become turgid/flaccid. The thin outer cell walls stretch more than the thick inner walls, this causes the two guard cells to bulge out and the stoma pore to open/close as the thick inner walls are pulled apart. Stomata usually open during daylight/darkness; this lets carbon dioxide enter the leaf and allows water loss by transpiration. Stomatal closing When water leaves the guard cells, they become turgid/flaccid. The guard cells no longer bulge outwards and the pore closes. This usually occurs during daylight/darkness and will conserve water at night. Plant Transport Structures Plants have two transport systems to move Water and minerals upwards from the roots XYLEM. Sugar to all parts of the plant (translocation) PHLOEM. 19

20 Structure of Xylem Xylem is dead tissue. - The xylem has hollow tubes to allow the movement of water. Hollow tube Spiral of lignin - The rings of lignin provide support. Structure of phloem Phloem is living tissue. Made of two types of cell, - Sieve tubes and Companion cells Sieve tube Sieve plate Nucleus Companion cell - Sieve tubes - transport sugar. - Companion cells - control both types of cell. Cytoplasm strands - Sieve plates - allow rapid transport of sugar - Strands of cytoplasm - help move sugar from one sieve tube to another. 20

21 Diagram of a root cross section to show xylem and phloem Diagram of a stem cross section to show xylem and phloem. Transpiration Roots All plant cells need water for many processes. Green plant cells need water for photosynthesis. The roots take up water they have a large surface area to allow the plants to take up sufficient water. Root hairs are single cells that greatly increase the surface area of the root allowing the plant to take in large amounts of water and minerals. Water is taken in to the root hairs by osmosis. 21

22 Transpiration The loss of water by evaporation from the leaves of a plant is called transpiration. The resulting flow of water through the plant is called the transpiration stream. Importance of the Transpiration Stream The transpiration stream is important because:- it carries water for photosynthesis to the cells in the leaves. the water carries essential minerals in solution evaporation from the leaves has a cooling effect. the water maintains turgor in cells to give the plant structure Plants play an important role in the water cycle, moving water from the soil into the atmosphere. Measuring Transpiration Transpiration rate can be measured by using a weight or a bubble potometer. The weight potometer allows the calculation of weight of water lost per unit time. 22

23 Water loss in a leafy twig under normal condition The weight potometer measures loss in mass due to water lost from plant through stomata. The bubble potometer allows the calculation of the rate of water uptake per unit time. Both potometers allow comparison of transpiration under different conditions. Conditions Affecting Transpiration Any abiotic factor that affects evaporation rate will affect the rate of Transpiration. Factor Effect on Transpiration Rate Increase/decrease/stay the same Temperature increase Temperature decrease Windspeed increase Humidity increase Light intensity Animal Transport Systems Learning Intentions To understand why multi-cellular organisms need transport systems To have knowledge of the organs involved in animal transport systems To label a heart and describe the flow of blood around the heart To know the names and structures of the vessels involved in transporting blood around the body To know the constituents of blood and their functions 23

24 To label the structures of the lung and understand their role in transport of gases. To understand the need for digestion To know the organs of the alimentary canal and their role in digestion To know what happens to the final products of digestion Circulation and the Heart The human heart is a simple but very efficient pump beating over 100,000 times a day. The four chambers, four valves and various blood vessels transport blood into and out of the heart. The heart is a double muscular pump - one side pumps blood around the body, the other to the lungs. Blood carries soluble food, gases, waste and hormones. Blood flows twice through the heart for each circuit. Use your e-book to diagram label the The wall of the left ventricle of the heart is thicker than the wall of the right ventricle because it has to pump blood all the way around the body but the right ventricle pumps it to the lungs (next door!) The function of the valves is to stop the back flow of blood in the heart. The heart muscle itself obtains a blood supply from the coronary artery. If it gets blocked then oxygen can t reach the heart muscle and the person has a heart attack. 24

25 Blood Vessels There are three types of blood vessel; - Arteries (away from the heart) - Veins (towards the heart) - Capillaries (between arteries and veins) Artery Vein Capillary Describe the differences between the three blood vessels. 25

26 Blood Blood is made up of several components. Complete the table showing the functions of the parts of the blood. Name of blood component Drawing of component structure Function of cell component Transports oxygen around the body N/A Yellow fluid that contains the blood cells, glucose and CO2 Platelets Clotting blood, forming scabs, stopping bleeding Red blood cells contain haemoglobin which traps oxygen and creates oxyhaemoglobin for transportation around the body. You should now be able to answer the following questions: a) Where, in the body, does haemoglobin become oxyhaemoglobin? b) Which type of cell will kill a cell that is infected with a virus? c) People who suffer from haemophilia bruise very quickly and cannot stop bleeding when cut. What component of blood is not working properly? d) Which famous family has haemophilia in its genes? e) Which gas, excreted by cells, is carried by the plasma to the lungs? 26

27 The Lungs Lungs are designed to be efficient at gas exchange. They are composed of many tubes, each ending in microscopic air sacs called alveoli. Air passes from the mouth to alveoli. The Alveoli Air 27

28 Alveoli are sacs are found at the end of bronchioles. They are the site of gas exchange in the lungs. Air sacs are lined with mucus and are surrounded by blood capillaries. The air sacs have a very large total surface area and a very good blood supply. Why are these things important? Use your e-book to answer the questions. Feature Importance Large surface area Moist Thin walls Rich blood supply Mucus and Cilia Mucus also lines the trachea and bronchi this sticky mucus traps any dust and micro-organisms which are breathed in. The cells that line the air tubes (trachea and bronchi) are covered in tiny hairs called cilia. They move back and forth to sweep the mucus upwards towards the throat. This helps to remove the dust and micro-organisms trapped by the mucus (the mucus is usually swallowed) Space for more notes 28

29 Digestion The purpose of digestion is to breakdown large insoluble particles of food, to small soluble particles. Allows food to be absorbed into the blood and transported to the cells. The main dietary components required by the body can be found in the table below. Food Group (Large Insoluble Food Molecule) Constituent Elements Basic Unit (Small Soluble Food Molecule) Contained Within Starch Protein Fat 29

30 The Model Gut The process of absorption can be demonstrated with a model gut. Starch is a large molecule made up of many small glucose molecules joined together. The starch glucose mixture represents.. The water represents. The visking tubing represents. What can we conclude about this experiment? The Alimentary Canal A long muscular tube that runs from the mouth to the anus. The digestive system has a number of organs attached to it. These add fluids to speed up the breakdown of food. 30

31 Part of Digestive Tract Function Mouth Oesophagus Stomach Small Intestine Large Intestine Rectum Label the diagram of the Alimentary Canal. Peristalsis is the muscular relaxation of the wall of the canal to push food along. contraction and alimentary The Stomach What is the purpose of the following cells? 31

32 Mucus Secreting Cell Acid Secreting Cell - Enzyme Secreting Cell - There are several organs that are associated with the Alimentary canal that have a role in digestion. These are called Associated Organs. Pancreas - Liver - Gall Bladder Digestive Fluids The many organs of the digestive tract produce a variety of digestive fluids containing digestive enzymes, as detailed in the following table. 32

33 The Small Intestine The small intestine s function is to absorb soluble food molecules and it is well suited to this job in a number of ways. - It is very long (About 6m). The inner surface is folded. - Each fold has thousands of finger-like villi to increase the surface area. - The lining of each villus is very thin. (Only one cell thick) - Each villus has a network of vessels for absorbing the food, both blood capillaries and lymphatic vessels. (Lacteals) The Villus Indicate on the diagram where glucose, fatty acids, glycerol and amino acids are absorbed. What are the benefits of the following? - a thin wall - a good blood supply - lacteal Fate of Absorbed Materials The glucose and the amino acids are absorbed into the blood capillaries, by the process of diffusion. These tiny blood capillaries all join up to form the hepatic portal vein and transport the absorbed food to the liver. The liver stores most of the glucose as glycogen until it is required, but some glucose remains in the blood. The amino acids are used in the body for growth and repair, but if there are any excess amino acids, these are broken down by the liver into urea. 33

34 This is later removed by the kidneys and released in the urine. Fats and fatty acids are absorbed by the lacteals which contain fluid called lymph. This lymph is transported in the lymph vessels which will eventually drain into the blood system. Lifestyle Choices Learning Intentions To understand the effects of lifestyle choices on animals transport and exchange systems To be able to identify that certain lifestyle choices can have a negative impact on peoples health. To be able to identify that certain lifestyle choices can have a positive impact on your health To identify the health risks individuals have with certain lifestyle choices. To investigate how exercise will affect an animals transport and exchange mechanisms To understand the need for vaccinations To debate the need for free NHS treatments for all diseases. Lifestyle Choices Make notes on the effects of the following lifestyle choices; High Fat Low Nutrient Diet High Salt Lack of Exercise Stress Smoking Alcohol Effects of Lifestyle Choices Bear in mind that some of these may not be due to lifestyle choice alone but can be linked to genes also, this means they are hereditary. 34