* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Calderglen High School Biology Unit 2 Multicellular Organisms
Embryonic stem cell wikipedia , lookup
Cell culture wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Cellular differentiation wikipedia , lookup
Artificial cell wikipedia , lookup
Human genetic resistance to malaria wikipedia , lookup
Dictyostelium discoideum wikipedia , lookup
Induced pluripotent stem cell wikipedia , lookup
Chimera (genetics) wikipedia , lookup
Cell (biology) wikipedia , lookup
Human embryogenesis wikipedia , lookup
Hematopoietic stem cell wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Precambrian body plans wikipedia , lookup
Regeneration in humans wikipedia , lookup
Microbial cooperation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cell theory wikipedia , lookup
Multicellular Organisms Calderglen High School Biology Unit 2 Multicellular Organisms 1 Multicellular Organisms Cells are the basic unit of live. Living organisms are composed of cells. Some organisms consist of one cell - unicellular organism. Multicellular organisms consist of many cells are more complex. Unicellular organisms Unicellular organisms include bacteria, some algae, some fungi and a group of organisms called protozoa. A unicellular organism called an Amobea bbc bitesize Multicellular Organisms These organisms are composed of many. The individual cells require food, oxygen and the removal of waste products such as carbon dioxide. However, a division of labour occurs amongst the cells. This means every cell does not carry out every function, specific cells become specialised to perform a particular function. Cell organisation The cells are organised as shown below Cells Tissues Eg muscle and bone. Organs Eg liver, eye or stomach Systems Eg circulatory system, digestive system Organisms 2 Multicellular Organisms Examples of Specialisation of Animal Cells Motor Neuron Image BBC Bitesize They have a long “tail” ideal for the transmission of nerve impulses. This ensures connections can be made with other cells. A protective sheath allows the nerve impulse to travel quickly from one end of the cell to the other. Sperm Cell Produced by male The cell has three parts. The head contains the nucleus, the mid- area contains many mitochondria and the tail allows the sperm to swim. Image BBC Bitesize Red Blood Cell Specialisation of Red blood cells which transport oxygen around the body. Scran image The cell produces haemoglobin The nucleus breaks down, leaving more space in the cell for the transport of oxygen. The cell has a large surface area to allow faster uptake of oxygen. Plants are organised in a similar way, examples of plant organs include leaves and flower. 3 Multicellular Organisms Examples of Specialisation of Plan Cells Plant Cells are organises in a similar way, examples of plant organs include leaves and flower. Examples of Specialisation of Plant Cells It consists of a companion cell and a sieve tube cell which transports sugar in the plant. The sugar produced by photosynthesis can transported to all parts of the plant in the companion cell. Phloem Tissue Sieve cell Sieve plate Companion cell These cells are adapted to their function because; Sieve plates (perforations) formed in the cell wall Phloem contains companion cells which control the activity of the sieve tube because the sieve tube does not contain a nucleus. Image BBC Bitesize Palisade Mesophyll Cell These cells are involves with photosynthesis and they form a continuous layer of cells near the leaf surface. These cells have become adapted for their function; The cells are column shaped The cells contain many chloroplasts to allow maximum photosynthesis Palisade mesophyll cell in a leaf Image – BBC Bitesize Image – BBC Bitesize 4 Multicellular Organisms A Root Hair Cell Root hairs absorb water and mineral salts form the soil. These substances move up the plant in the xylem. Root hairs are adapted for their function because they are Root hair cell Image – BBC Bitesize Lacking in chloroplasts because root hairs are underground in the soil. The shape of the cell ensures a large surface area for absorption of water and mineral salts. The presence of the vacuole in the extended section of the root hair gives rise to absorption of mineral salts and the movement of water into the hair by osmosis. 5 Multicellular Organisms Stem Cells and Meristems The cells of an organism contain 2 sets of chromosomes (except sex cells) for example human cells contain 2 sets of 23 chromosomes making 46 in total. However some genes on a chromosome will be switched on or off to form specialised cells in different tissues, organs and systems. This happens early in the cells development and is irreversible. The cells specialised cells originate from are called stem cells and these can become any type of cell e.g. red blood cell, nerve cell or bone cell. Stem cells are needed as an organism grows and to replace damaged cells. Liver Image BBC Bitesize Bone Nerve Red blood cell Stem cells can be extracted from early human embryos or from bone marrow or the blood circulation. Using tissue culture techniques they can be induced to form differentiated cells. Recent research has also found ways to reverse some specialised adult cells back to stem cells. Possible uses of stem cells include the treatment of diabetes and cancer. Repair to body organs including bone and the windpipe or even the growth of organs for transplant such as liver and skin. Another area of possible use is stem cells could be used to grow tissues to test the effect of toxins such as pesticides sprayed on crops. The problem is how to make the undifferentiated stem cells into the specialised cells required. Scientists are making big steps in this area but work still needs to be done. Stem cells that turn into blood cells are called haematopoietic stem cells and can be used to form red blood cells, white blood cells or platelets. 6 Multicellular Organisms A specific example of stem cell use Brain diseases – stem cells from embryo‟s have been programmed to form brain cells that can replace damaged ones. This could help diseases such as Parkinson‟s where damage to nervous tissue leads to muscle spasms caused by continual muscle contraction. Replacement cells could also be used for Alzheimer‟s disease where damaged brain cells cause memory loss and confusion. Ethical Issues Some people object to the use of embryos on moral or religious grounds arguing this is a loss of potential human life. This has to be balanced against the prevention and release from suffering the stem cells could bring. Some religions are strongly against the use of stem cells Meristems Plants contain regions of undifferentiated cells (non-specialised cells) in regions called Meristems. These Meristems are the only region in plants where cell division occurs (by mitosis). They have the potential to become any type of cell and they contribute to plant growth. The cells in the meristem become elongated (longer) and vacuolated (vacuoles appear) and then differentiated. Differentiation is when the unspecialised cells become specialised, e.g. they may become long hollow tubes called xylems that carry water upwards from the roots in plants. 7 Multicellular Organisms Control and Communication In a multicellular organism, cells communicate using nerve impulses or hormones. The central nervous system produces electrical impulses for rapid communication between different parts of the body. Nervous control The brain and spinal cord are made of neurons. The brain and the spinal cord make up the central nervous system (CNS). Many nerves join with the CNS. They bring messages as nerve impulses from sensory organs which contain cells called receptors. The CNS sorts this information and processes it. To trigger a response, a different group of nerves are used to carry messages from the CNS to effectors which are usually muscles. image bbc bitesize 8 Multicellular Organisms The Brain The brain plays a very important part in the way you respond to any factors that may affect your body. Just to read this page, millions of nerve messages are zipping around within your own brain. The brain itself is made up of several different parts or regions, each with its own specialised function. image bbc bitesize Part of the brain Function Cerebrum Controls conscious actions, as well as reasoning and learning. Cerebellum Balance and muscle co-ordination Medulla Controls the rate of breathing and heartbeat. 9 Multicellular Organisms Nerve pathways It involves three types of nerve cell or neurons. Neurons are highly specialised because they carry electrical impulses, they do not come in contact with one another: A sensory neuron which carries electrical impulses from a sense organ to the CNS. A relay neuron which is located in the brain or spinal cord. It receives electrical impulses from the sensory neuron and transmits them to other nerve cells involved in the response. A motor neuron which receives electrical impulses from relay nerve cells and transmits them to a muscle or gland which will carry out the response. When stimulated by an electrical impulse, muscles respond by contract and glands by releasing chemicals. Muscle responds more rapidly than glands. Reflex actions are fast responses that do not normally involve conscious thought. They usually protect your body from harm. Examples of reflex actions include sneezing when foreign particles enter the nose, withdrawal of a hand from a hot object, blinking when an object moves near the eye. The circuit of the neurons that act to produce the reflex action is called the reflex arc (refer to the diagram on the next page) 10 Multicellular Organisms Image from BBC Bitesize Relay neuron Sensory neuron Motor neuron muscle Burning candle Reflex arc The transmission of a nerve impulse through a reflex arc is called a reflex action. In the example above the sensory neuron in the hand detects the heat and this initiates an electrical impulse which travels towards the relay nerve. The impulse is transferred to the rely nerve which passes on the impulse to the motor nerve. The nerve impulse travels along the motor nerve to the muscle which brings about a muscle contraction and the hand is withdrawn from the heat. The neurons do not touch, there is a small gap called a synapse between neurons which allows chemicals to transfer from one neuron to another. Sensory neuron Relay neuron Motor neuron Synapse (gap Synapse (gap between neurons) between neurons) 11 Multicellular Organisms Hormonal control Hormones are made up of proteins. They are chemical messengers which pass on information to target tissues which have special receptor cells sensitive to that specific hormone. Only some tissues are affected by specific hormones. Glands which release hormones into the bloodstream are known as endocrine glands. Endocrine system Image from BBC Bitesize Pancreas Liver Testes (male) Ovary 12 Multicellular Organisms Regulation of Blood Glucose Level in the Blood Cells are constantly using up glucose present in the bloodstream for energy. A rise in blood glucose concentration is detected by cells in the pancreas. These cells produce the hormone insulin. This hormone is transported in the blood to the liver where it activates glucose to be converted to glycogen. This brings blood glucose concentration down to around its Scran image normal level. If the blood glucose concentration drops a different set of cells in the pancreas detect this change and release the hormone glucagon into the bloodstream. This second hormone is transported to the liver and activates the conversion of glycogen to glucose. The blood glucose concentration therefore rises to its normal level. Regulation of Blood Glucose levels Insulin produced when blood glucose level is above the normal level blood glucose level Glycogen in the liver Glucagon is produced when the blood glucose level falls below the normal level 13 Multicellular Organisms Diploid Cells After fertilisation, a zygote (fertilised egg) is formed. The cell is DIPLOID A diploid cell has 2 sets of chromosomes (in humans this is 46 chromosomes). One set has come from the male parent and one set has come from the female parent. Every body cell has a copy of the chromosomes that was in the zygote. Therefore, every body cell is a diploid cell. The diploid number in humans is 46. Haploid Cells Eventually, the adult will produce sex cells. Another name for the sex cells is GAMETE. Gametes will only have one set of chromosomes. A HAPLOID cell has only one set of chromosomes The haploid number in humans is 23. Fertilisation If a haploid gamete from a male meets a haploid gamete from a female, a diploid zygote is formed. Haploid Haploid Gamete eg Gamete eg sperm egg Fertilisation produces a diploid zygote 14 Multicellular Organisms Gamete Production in Animals Like plants, animals produce gametes in sex organs. In human males, SPERM are produced in the TESTES. In human females, EGGS (ova) are produced in the OVARIES. Millions of sperm cells are produced in the testes and are able to swim in fluid using their long tails. Egg cells are the largest human cells because of the large food store in the cytoplasm. Sperm (male gamete) Egg (female gamete) head tail Cell membrane nucleus Cytoplasm containing a food store Scran images 15 Multicellular Organisms Animal Reproductive System Male reproductive system image bbc bite size sperm duct penis Testes Female reproductive system image bbc bitesize testes ovary womb Sexual Reproduction in Plants Flowers are the organs of sexual reproduction in plants. The flower contains both the male and female parts. The ANTHER and FILAMENT together is known as the STAMEN. This is the male parts of the flower. The male anther is the site of gamete production. The diploid anther cells produce the haploid pollen grains, which contain the male gametes. The OVARY is the female part of the flower. The female ovary is the site of gamete production. The diploid ovary cells produce haploid eggs (the female sex cell or gamete). 16 Multicellular Organisms Variation A characteristic shows DISCRETE VARIATION if it can be used to divide up the members of a species into two or more distinct groups. Humans can be split up into two groups depending on their ability to roll their tongue and into four groups based on blood group types A, B, AB and O. Data obtained from a survey of a characteristic that shows discrete variation is represented by a bar chart Discrete variation graph Image bbc bitesize Some characteristics are controlled by the alleles of a single gene – they are expressed as clear-cut PHENOTYPIC groups showing discrete variation. In humans, the ability to roll the tongue is an example of the single gene inheritance. In pea plants, the possession of lilac or white flowers is an example of single gene inheritance. 17 Multicellular Organisms Continuous Variation A characteristic shows continuous variation when it varies amongst the members of a species in a smooth, continuous way from one extreme to another and does not fall into distinct groups. CONTINUOUS VARIATION can be represented by a normal DISTRIBUTION CURVE (the curve would be bell shaped). Image bbc bitesize Few individuals show values close to the extremes of the range. Most individuals show values close to the middle of the range (also known as the average). Some characteristics are controlled by the alleles of several genes. This results in the characteristic being expressed as a range of PHENOTYPES e.g. Human height. A characteristic showing CONTINUOUS VARIATION controlled in this way by more than one gene is said to show polygenic inheritance. 18 Multicellular Organisms Phenotypes and Dominant Genes For every characteristic we have 2 genes – one from our mother and one from our father. Genes are part of chromosomes. Each characteristic is controlled by two forms of a gene. Each parent contributes one form of the gene. Each gamete (sex cell) carriers one of the two forms of the gene. Differing forms of a gene are called ALLELES. Example – The alleles for the gene for eye colour are blue, brown, green, etc. PHENOTYPE – this is the physical appearance resulting from the inherited information. Example – Someone with blue eyes has the phenotype blue eyes. Genes or alleles can be said to be DOMINANT (shows up in the phenotype) or RECESSIVE (hidden when it is present along with the dominant gene). GENOTYPE – this is the combination of genes in a gene pair. Genotype is represented by 2 letters (one letter for each gene). Note – the phenotype of this individual is Black Hair Dominant black gene Recessive white gene If the 2 alleles that an organism possesses for a characteristic are identical, the organism is said to be HOMOZYGOUS for the characteristic. BB has a phenotype black it is said to have a HOMOZYGOUS genotype. Homozygous is often called „pure breed‟ or „true breeding‟. Bb has the phenotype black but it is said to have a HETEROZYGOUS genotype. If the 2 alleles that an organism possesses for a characteristic are different, the organism is said to be HETEROZYGOUS for that characteristic. bb has the phenotype white and is said to be HOMOZYGOUS recessive. 19 Multicellular Organisms Genetic Crosses A genetic cross is laid out as follows: A pea plant which produces round pea seeds is crossed with a pea plant which produces wrinkled pea seeds. All the offspring are round. R: Round r: Wrinkled Parents Phenotype (P) Round Parents Genotype (P) RR Gametes X Wrinkled X R X First Generation (F1) Genotype Rr First Generation (F1) Phenotype Round F1 X F1 = Rr Gametes R,r Genotype RR Rr X Rr rr r Rr R, r rr Second Generation (F2) Phenotype Round Round Round Wrinkled Second Generation (F2) F2 Phenotypic ratio 3 : 1 The actual ratio may differ from the expected ratio since fertilisation is a random process. An element of chance is involved. 20 Multicellular Organisms Need for Transport systems in Plants As an object increases in size the surface area to volume ratio decreases. This means a larger object has to be supplied with nutrients using a transport system Transport of water in plants Root Hair Cell Image BBC Bitesize The root hair is an extension of the root cell and water is taken in by osmosis through the cells selectively permeable membrane. When this cell has taken on a reasonable amount of water it will have a higher water concentration than the next cell and so water will pass to this next cell by osmosis. This process continues until the water reaches specialised water transport vessels called xylem. Image – BBC Bitesize Root epidermal Xylem cell vessel Water travels across the root cortex cells by osmosis and then enters the xylem vessels. 21 Multicellular Organisms Xylem Water and minerals are transported from the roots upwards to the leaves. Xylem forms when the nucleus and end walls of the cells disintegrate forming long hollow lignified tubes. Xylem is a nonliving material. Rings of lignin (give plant support) Image – BBC Bitesize Water movement in xylem vessels Transpiration is the evaporation of water from the mesophyll cells in the leaves of plants. Water evaporates through stomata whose opening and closing is controlled by guard cells, which are found in the leaf epidermis (outer layer of cells). In order to replace this lost water, water is pulled up through the xylem vessels (transpiration stream). Mesophyll cells in the leaf require water for photosynthesis and this is delivered via the xylem vessels. Section of leaf Mesophyll cell in the leaf Air space in Xylem leaf Lower epidermis Stoma Guard cell Image – BBC Bitesize 22 Multicellular Organisms Factors affecting transpiration The following factors affect the rate of transpiration; temperature, humidity, air movement and light. These factors are known as abiotic factors. Abiotic factor Transpiration rate Temperature Light intensity Air movement Humidity An increase in any of these factors will result in an increase in the rate of transpiration An increase humidity will result in decrease in the rate of transpiration Opening and closing of stomata When the guard cells become turgid this forces the stoma open. When the guard cells are flaccid the stoma closes. guard cells stoma epidermis Stoma open Stoma closed Images – BBC Bitesize 23 Multicellular Organisms Diagram of a leaf showing the position of the stoma. Image BBC Bitesize stoma Transport of sugar in plants Sugar is transported up and down the plant in living phloem cells. Sieve plate Image -BBC Bitesize Companion cell Sieve cell Differences between Xylem and phloem Xylem Phloem Transports water and minerals dead lignified No companion cell No sieve plates Transports sugar living Not lignified Companion cell Sieve plates 24 Multicellular Organisms Transport Systems in Animals Blood consist of two parts Plasma Other blood cells The role of blood Blood consists of blood cells and the fluid that surrounds them called plasma. Many substances are transported dissolved in plasma including glucose and amino acids. Red blood cells Red blood cells transport oxygen from the lungs to body cells. The pigment haemoglobin found in the red cells reacts with oxygen at the lungs to form oxyhaemoglobin. At the tissues the oxygen is released to diffuse into the cells. Red blood cells have no nucleus In order to maximise the space available to carry oxygen. They are very small to fit through the smallest blood vessels and have a biconcave shape that increases their surface area. Image source SCRAN Red blood cells In mammals the main transport system is the circulatory system, comprising of the heart and associated blood vessels. The heart is a muscular pump, pumping blood around the body to deliver nutrients and oxygen as well as dispose of carbon dioxide and waste. The wall of the left ventricle is thicker than that of the right because it has to pump blood all round the body. 25 Multicellular Organisms Structure of the heart Valve at exit to Valve at exit to pulmonary artery aorta Right atrium Left atrium Right ventricle Left ventricle Image from BBC Bitesize Valves between atria and ventricles Valves in the heart and in veins prevent the backflow of blood 26 Multicellular Organisms Circulation Pulmonary vein aorta Pulmonary artery Image from BBC Bitesize Vena cava Deoxygenated blood Oxygenated blood The Coronary artery The first branch of the aorta leaving the heart is the coronary artery and this supplies the heart muscle with oxygenated blood. The diagram on the right also shows how a build up of lipid material called plaques can lead to a coronary heart attack. A heart Coronary artery 27 Multicellular Organisms Blood Vessels Arteries carry blood away from the heart. They have a thick muscular wall and a narrow central channel. The blood in arteries is under high pressure. Veins carry blood towards the heart they have a thinner muscular wall than arteries and a wider central channel. The blood in veins is under low pressure and they contain valves to prevent backflow. Artery Vein Thin muscular Valve wall Thick muscular wall Wide Direction of central blood flow channel Capillary Thin central channel Capillaries are exchange vessels. Their walls are only one cell thick to allow materials to cross from tissues to capillaries easily. There is a dense network of capillaries giving a large surface area. Examples of materials that cross capillary walls are oxygen and glucose into cells and carbon dioxide and urea from cells to the capillary. 28 Multicellular Organisms The Lungs Function of the lungs The lungs are organs of gas exchange. Blood from the body is pumped from the heart to the lungs via the pulmonary artery. This blood is rich in carbon dioxide and low in oxygen (deoxygenated). At the lungs gas exchange takes place carbon dioxide diffuses from capillaries into the alveoli and oxygen diffuses from the alveoli into the capillaries. This oxygenated blood is then returned to the heart via the pulmonary vein. From the left ventricle it is then distributed round the body via the aorta. The Lungs trachea rings of cartilage lung airways inside the lungs alveoli Deoxygenated blood Air in Air out Oxygenated blood Alveolus and the large capillary network 29 Multicellular Organisms An alveolus showing gas exchange Image from scran deoxygenated blood oxygenated blood O2 Red blood cell Feature of a gas exchange surface Feature large surface area moist surface thin lining surrounded by large capillary network CO2 moisture layer Function to absorb oxygen allows oxygen to dissolve eases diffusion of oxygen into blood to pick up and transport oxygen 30 Multicellular Organisms Function of rings of cartilage The incomplete rings of cartilage in the bronchi and trachea ensure they remain permanently open at all times. Function of cilia and mucus The trachea and bronchi are lined with tiny hairs called cilia and glandular cells that secrete stick mucus. The cilia beat rhythmically sweeping mucus with trapped micro-organisms upwards into the larynx from where they pass into the stomach via the oesophagus, to be destroyed by stomach acid. cilia Image BBC Bitesize 31 Multicellular Organisms Digestive System The digestive system includes the alimentary canal running from the mouth to the anus and associated organs including the liver, pancreas, salivary glands gall bladder. oesophagus liver stomach pancreas large intestine small intestine anus Image from SCRAN 32 Multicellular Organisms Peristalsis Food moves through the digestive system by a method called peristalsis. This involves circular muscles behind the food bolus contracting while those in front of the food relax and the food is pushed forward. Once food has passed down the oesophagus it enters the stomach. Churning now occurs- this involves stomach wall muscles mixing food with digestive juices. Food is released from the stomach and passes into the Muscles small intestine where contract absorption takes place. Ball of oesophagus food Muscles in front of the food relax and the ball of food moves forward Image BBC Bitesize The small intestine has several features facilitating absorption. It is very long The internal surface is folded and has thousands of finger like projections called villi. (The small intestine has a large surface area for the absorption of food). The small intestine has a good blood supply to carry away the products of digestion. 33 Multicellular Organisms Structure of a villus Thin wall of the villus Blood capillary absorbs glucose and amino acids Lacteal – Absorbs the products of fat digestion called fatty acids and glycerol Image from SCRAN Image Scran The villi in the small intestine are adapted for the absorption because they are thin walled a large surface area good blood supply The villus wall consists of a one cell thick layer of epithelial cells so the end products of digestion can easily pass through. Glucose and amino acids pass into the blood capillaries and the products of fat digestion enter the lacteal. 34