National 5 Biology Unit 2 notes

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present in a cell If a cell contains 2 sets of chromosomes, the cell's chromosome complement is said to be diploid. O Example: Human body cell have 2 sets of 23 chromosomes, therefore the cell is referred as diploid & the chromosome complement = 46 ● Mitosis maintains the chromosome complement of the cells. This is important because new cells must have the same genetic info as the original cell. To make sure that the daughter cells get the same info as their mother cell, the mother cell's chromosome must replicate before mitosis occurs. d. Stem Cells A type of cell used to create specialised cells through differentiation. Stem cells are able to replicate itself through self-renewal, so that your body doesn't run out of stem cells. Stem cells are important because : o They make new cells to replace cells that die in your body daily also help you grow O They make new cells to repair tissue damage (Example : Broken bones) There are 2 types of stem cells 1. Embryonic Stem Cells: Are able to become any type of cell in your body 2. Tissue Stem Cells: Only able to become a few types of cells depending on what tissue stem cells it is. Tissue stem cell e.g. blood stem cell Embryonic stem cell Differentiation Differentiation A few types of specialised cells e.g. blood stem cells can become red blood cells, white cells or the cells that form platelets Figure 1.4: Differentiation in tissue stem cells All types of cell in the body Figure 1.5: Differentiation in embryonic stem cells 3 NOTE: For tissue stem cells, you can only become types of cells in that category. Example: Skin stem cells can make skin cells and blood stem cells can make red blood cells. Skin stem cells CANNOT make red blood cells and blood stem cells CANNOT make skin cells. Specialised cell O A type of cell which does a particular function in the body O Specialised cells cannot replicate themselves therefore they require stem cells. Example: Red Blood Cell. O Differentiation (Different: iation) O e. Example of specialised cells Unicellular Organisms nucleus The process where stem cells becomes specialised cells. cytoplasm contractile vacuole nucleus cell membrane Amoeba Unicellular Organism chloroplast cell membrane Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display whip-like flagellum O cytoplasm food vacuoles pseudopod Euglena Features Plant and animal like features. Flagellum for swimming. Chloroplasts for photosynthesis. Can take up food by phagocytosis. Has a light sensitive eye-spot Amoeba Very primitive unicellular organism. Moves by changing its body shape. Amoeba feed by flowing around food such as bacteria. This process is called phagocytosis. 4 Multicellular Organisms Table 1.2: Examples of specialised cells in multicellular organisms (Images courtesy of BBC Bitesize) Diagram Details Cytoplasm End wall Companion cell Sieve tube Cal membrane Dendrite Nucleus 7 μm Nerve ending Top View shows RBC to be circular Side view shows RBC to be a biconcaved disc Nerve cell (Neuron) ● Highly specialised to carry electrical impulses around the body of an animal. Can be many meters long. insulating material to aid transmission of electrical impulse. . Produce Red Blood Cell Biconcave disc shape- gives a large-surface area to volume, so RBC can absorb and release oxygen faster. • Cytoplasm contains lots of haemoglobin, which binds to oxygen and allows RBCs to transport oxygen efficiently. Lack a nucleus when mature more space for carrying oxygen. Root hair cell Found in the epidermal (outer) tissue of plant roots. • Its outgrowth (called a root hair) gives the cell a large surface area so that it can efficiently absorb water and nutrients from the soil. ● Phloem sieve tube and companion cells • Phloem transport sugar through (flowering) plants. End walls have pores to make movement of materials easier. Lack a nucleus. • The companion cell controls the activity of the phloem. 5 f. Levels of cellular organisation in multicellular organism A tissue is a group of specialised cells that work together for a particular purpose. ● An organ is a group of tissues that work together for a common purpose. Example of tissue in animals Tissue Muscular Glandular Epithelial Cells Tissues Organs→ Systems Blood Tissue Example tissues in plants Function Contracts, bringing about movement. Produces and releases substances such as hormones. Organisms Cover the internal and external surfaces and cavities of the body. Transports oxygen, glucose, carbon dioxide, hormones, amino acids, antibodies and many other substances around the body. Phloem vascular tissue Xylem vascular tissue Function Transports dissolved sugars from the leaves to growth points. Transports water and nutrients from roots to leaves. 6 Example of organs systems in animals System Digestive Immune Respiratory Circulatory Nervous Function Breaks down food into smaller molecules that can be absorbed into the body. Prevents pathogens from infecting the body to cause disease. It produces white blood cells to detect and destroy pathogens. Where oxygen is absorbed into the body and carbon dioxide is released. Transports oxygen, nutrients and water to body cells. Transports waste materials including carbon dioxide away from cells. Responsible for sending, receiving, and interpreting information from all parts of the body. The nervous system monitors and coordinates internal organ function and responds to changes in the external environment. To produce gametes (egg and sperm cells), to transport Reproductive and sustain these cells, to nurture the developing offspring, and to produce hormones with the goal to produce offspring. NOTE: A chromosome made of 2 identical chromatids. There are 2 types of stem cells and don't mix them up. Cells Tissues Organs Systems Organisms Try to remember a few examples from each section. Examples of organs from system Salivary glands Stomach Small intestine Large intestine Skin Spleen Trachea Bronchi Lungs Heart Renal artery Pulmonary vein Brain Spinal cord Ovary Testis Uterus 7 a. Nervous Control Central Nervous System (CNS) Made up by: Brain, Spinal Cord & Nerve Cells CNS have 2 main functions Neurons 1. Process info received from the senses 2. Coordinate the body's response. To achieve the 2 main functions CNS receive info from specialised receptors. Ch.2 Control & Communication Specialised nerve cells to carry info in an electrical nerve impulses form. Example of receptor Receptor Photoreceptor Thermoreceptor Chemoreceptors Receptors e.g. light-receptor cells in the eyes Receptors CNS Effectors Stimulus e.g. bright light Retina in eye Skin and hypothalamus (region of brain) Tongue and nose Location There are 3 types of neurons: 1. Sensory Neurons : Carry electrical impulses from receptors to the CNS 2. Inter Neurons : Locate in the CNS, transmit the electrical impulses from sensory to motor neurons. 3. Motor Neurons : Carry electrical impulses from CNS to the effectors. Sensory Neuron Inter Neuron Stimulus Light Temperature Motor Neuron Chemicals Effectors e.g. muscles which control the iris Response e.g, iris constricts reducing light entering the eye 8 Each neuron is made up of 3 parts: 1. Cell Body (Cytoplasm + nucleus) 2. Fibres that carry the impulses into the cell body 3. Fibres that carry the impulses away from the cell body. The Brain sensory neurone Synapses O O O Sensory Neuron Hypothalamus Medulla The gap between neurons. When an impulse arrives at a synapse, it will cause diffusion of a chemical substance. This chemical substance allows the impulse to travel the gap & triggers the nerve impulse in the next neuron. (cerebral hemispheres) fatty sheath Medulla cell body Cerebellum direction of impulse Function of different parts of the brain (MUST REMEMBER !!!!) Region of brain Cerebrum SYNAPSE nucleus diffusion of chemical Cerebrum Cerebellum Function Inter Neuron Controls language, memory, personality and conscious thought Controls heart rate and breathing rate Controls balance and co-ordination of movement 9 Function of the brain O O O O Reflex Actions Reflex action is: Rapid O Automatic Protective O Involuntary (unable to be ignore / controlled) O O Receives impulses from all sensory organs Sends motor impulses to effectors organs to control their functions Coordinate the movement of the body Stores info. During a reflex action, the impulse goes to the spinal cord, not the brain, before making a response. A reflex action doesn't require the brain's conscious control. Example of reflex action Reflex action Sneezing Pupil reflex Knee jerk Stimulus Irritant material on membranes of airways Light intensity Tapping patellar tendon Response Sudden contraction of diaphragm and intercostal muscles Protective function Lower leg kicks forwards due to sudden contraction of front thigh muscles Causes a violent expiration to blow irritant material out. Iris muscles adjust Controls light intensity, pupil diameter, wide in protecting retina from damage dim light, narrow in bright light. Protects the tendon 10 Reflex Arcs ● The structure that is responsible for reflex action makes up the reflex arc. Receptor Sensory Neuron <Synapse> Inter Neuron <Synapse> Motor Neuron → Effector muscle b. Hormonal Control Hormone start here O 2 1. candle flame 5. -Hormone 3 A chemical messenger released into the bloodstream by endocrine glands. O Specific hormone can affect its specific cell (target cell) which has a complementary protein receptor. muscle Target cell 11 Examples of hormone production & effect in humans Hormone Insulin Glucagon Where produced c. Blood glucose regulation If glucose concentration Pancreas is: Pancreas Glucose is needed by cells for respiration. TOO HIGH TOO LOW Target organ NOTE: These 2 are important as the SQA requires us to understand the conversion between glycogen & glucose. ● Insulin & Glucagon are hormones produced by the pancreas that regulate the level of glucose in the blood. Pancreas will: Liver Liver Increase the amount of INSULIN into the bloodstream While glucagon will decrease. bloodstream Increase the amount of GLUCAGON into the While insulin will decrease. Triggers the production of enzymes which converts glucose to glycogen. Triggers the production of enzymes which converts glycogen to glucose. Effect Liver will then: Converts GLUCOSE to GLYCOGEN & stores it. Liver will also stop converting the stored glycogen to glucose Converting the stored glycogen to glucose. Liver will stop converting glucose to glycogen Therefore the glucose level blood will: Decrease Increase 12 Diabetes Raises blood sugar Glycogen O Liver O Stimulates glycogen breakdown Type 1 diabetes O O Glucose Stimulates glycogen formation Lowers blood sugar There are 2 types of diabetes: 1. Type 1 diabetes 2. Type 2 diabetes High blood sugar Tissue cells Glucagon Insulin NOTE: To make it simpler: • If there's too much glucose in the bloodstream, pancreas will create more insulin because insulin can convert glucose to glycogen. Stimulates glucose uptake from blood Low blood sugar If there's too little glucose in the bloodstream, pancreas will create more glucagon because glucagon can convert glycogen to glucose. Promotes insulin release Type 2 diabetes O Cause by a person's body resistant to insulin Can be controlled by diet & exercise. A link between obesity with type 2 diabetes. Pancreas Promotes glucagon release Caused by failure to produce insulin People who have it need to monitor their diet & inject insulin regularly 13 NOTE: The structure and function of brain must remember Hormones are chemical messengers. Hormones are specific to a protein. 14 NOTE: Reproduction is the addition of new members to a species. Human cells are diploid (it have 2 sets of chromosomes) Only gametes are haploid (only have 1 set of chromosomes) Diploid = 43 chromosomes Haploid = 23 chromosomes a. Gametes (Sex cells) Gamete production in humans Penis Urethra Sex cell Name of organ producing sex cell • Sperm (male gamete) o Large number o Small gametes Ch.3 Reproduction Ova (female gamete) O Small number o Large gamete Bladder Sperm duct Testis Enzyme packet Female Ovary Ova (egg) Ovary a) Oviduct 'Head' containing nucleus 'Tail' 'Neck' Nucleus 'Jelly layer' Uterus Vagina Male Sperm Testis b) Cytoplasm Cell membrane 15 Gamete production in flower plants Petal Structure containing sex cell Organ producing sex cell Stigma Cara Female Ovule Ovary Nectary Anther Pollen grains Ovary Ovule Male Pollen grain Anther ● Each flower contains both male & female reproductive organs, but they released their male & female gametes at different times to prevent self-fertilisation. 16 b. Fertilisation Gametes don't contain enough genetic info to produce a new individual, therefore to produce a new individual, 2 gametes must fuse together to produce a new individual. Fertilisation in humans ● When a sperm reaches an egg, the sperm's nucleus enters the egg & fused with the nucleus of the egg. This fused cell is called a zygote which is diploid. The zygote then will begin to duplicate and form an embryo. Haploid Egg (Ovum) fertilisation ● Fertilisation is a random process. ovum is moved along the oviduct 23 chromosomes Ovum the oviduct Fertilisation p by ↓↓ Human fertilisation occurs in the oviduct of the female. oviduct --0-0 Sperm 23 chromosomes Ovum is released by the ovary - ovulation Zygote 46 chromosomes in 23 pairs Embryo 46 chromosomes in 23 pairs ovary Haploid Diploid Diploid uterus Sperm swim through uterus towards oviduct 17 Fertilisation in plants Pollen grains must be transferred from one flower to another through pollination. ● ● Once the pollen grain lands on the stigma, it forms a pollen tube. The pollen tube will then grow down to the ovary, which enables the pollen grain to reach the ovule for fertilisation to occur. After fertilisation Ovule becomes seed o Ovary becomes fruit. O Pollen grain Pollen tube Pollen nucleus Ovary Ovule 18 NOTE: Each parent has 2 sets of chromosomes but each parent only will randomly pass down 1 set of the chromosomes to their child. Fertilisation is a random process. Some characteristics are due to genetic influences (inherited characteristics), and some are due to the environment around (acquired characteristics). Phenotypes: an organism's inherited characteristic. a. Continuous & Discrete variation Ch.4 Variation & Inheritance ● Variation : Differences between individuals in a population that are not cause by accident / disease. There are 2 types of variation: O Continuous Discrete O Conti uous variation ● Phenotypes of a character which takes a wide range of values. Example: O Human height o Body mass O Foot length (This is not foot size !) Continuous variation is shown through histogram. Height category (cm) 19 Discrete variation ● ● A limited number of phenotypes / possible values. Example: O Gender O Blood group o Eye colour Discrete variation is shown through the bar chart. Percent of population 50 6 I.. B Blood group AB 0 20 b. Genetic key terms (these all need to be memorised) Term Genes P/F₁/F₂ Phenotype Genotype Genotype of gamete Alleles Homozygous (a.k.a True breeding) (Homo:zygous) Heterozygous (Hetero:zygous) A section of DNA which codes for a specific protein. Definition & Notes Parents / 1st generation offspring / 2nd generation offspring of an organism The appearance Example: Tongue roller A complete set of genes processed by an organism. Indicated by using 2 symbol Example: TT/Tt The genetics that make-up the gamete. Indicated by 1 symbol Often indicated with a circle around the symbol. Example: Ⓒ Note: Gametes only have 1 set of chromosomes. The different forms of a gene Example: T & t are both alleles for tongue rolling genes. The 2 alleles are the same Example: TT /tt The 2 alleles are different Example: Tt 21 Dominant Recessive Polygenic inheritance (Poly:genic) Monohybrid inheritance (Mono:hybrid) The allele that shows in the phenotype of heterozygous. Example: Tt (T is dominant) The dominant allele is usually indicated with a capital letter. The allele that is masked in the heterozygous. Example: Tt (t is recessive) The recessive is indicated with a small letter. Several genes are involved in the inheritance of a characteristic. This means there's a range of phenotypes showing continuous variation. Is responsible for the majority features of an organism's phenotype. A phenotype controlled by one single gene. Example: Attached / unattached earlobes This will result as discrete variation 22 c. Monohybrid crosses • Monohybrid inheritance: A phenotype controlled by one gene and will result as a discrete variation. I III ● 1 HH 2 ¹Hh 2 Hh hh 1 2 3 4 5 HH hh hh Hry HH Hh Hh /Hh 3 hh 4HH Hh Ĥh Red Hair Female Red Hair Male Non Red Hair Male O Non Red Hair Female Let H-Allele { no red hair Leth=Allele f red hai From this we see that, even though in the F₁ generation no one physically has red hair, they still had the genes for red hair which in result was passed on to their offspring. • Fertilisation is a random process. Pea experiment Through the experiment, we found out that genetics will pass on even if it wasn't physically shown on a person. • Why peas? 1. Peas life span is short therefore scientists are able to look at many generations in a short period of time. 2. Produce a large number of offspring, therefore the ratios are more reliable 3. Possess certain characteristics which will always show discrete variation. 23 ● Results: 2nd P: TT X 20 Gametes: T cross F₁: d. Punnett Square P₂: Gametes: Tt T t Tt X tt T t and Phenotypic ratio: 3 Tall: 1 Dwarf Genotyping ratio : 1 TT: 2 Tt: 1 tt Tt ● Used to work out the phenotypic and genotypic ratio. • Example (ref. to the pea results) T T TT Tt Alleles: t Tt tt T = Tall t = Dwarf NOTE: The predicted rations doesn't happen that much in reality because fertilisation is a random process. 24 a. Plant organs Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Vein Guard cell Ch.5 Transport Systems - Plant Stoma ● Plant have 2 types of transport tissue: o Xylem O Phloem These 2 form a vein of a plant. Made of dead cells Xylem ● Involved in the movement of water through plant from roots to leaves Have thick cellulose cell walls strengthened by lignin rings / spirals. ● Water moves into the plant through root cells ● Water moves into the plant through osmosis. Root cells are covered with root hair cells to increase the surface area. By increasing the surface area, it increases the rate of water moving into the int. Route of water in plant: Root Xylem (Stem) → Leaves Lignin spirals 25 0000000000000 Xylem Phloem ● ● ● Used to transport sugar from leaves (generally) to where it's needed (e.g. Growing areas). • Can go up and down the plant freely. Made of living cells Contain sieve controlled by companion cells b. Transpiration (Trans:pirat:ion) ● The process of water movement through a plant. Upper Epidermis Mesophyll Lower Epidermis NOTE: This is the movement of water in a plant, osmosis is how the water enters the plant. Space Stoma to Guard Cell with Chloroplasts Wax Cuticle Palisade Mesophyll Phloem Spongy Mesophyll Wax Cuticle Guard cells (swollen/turgid) Stoma open End walls Water evaporates from the stoma which is controlled by the guard cell. ● Root Xylem(Stem) →Leaves -(Evaporates)-> Atmosphere Companion cells Sieve tube Guard cells (shrunken/flaccid) 63 Stoma Closed -Chloroplast -Cell Wall -Vacuole -Nucleus 26 Factors that can affect the rate of transpiration Factor Surface Area Temperature Wind Speed Humidity Effect As surface area increases, transpiration rate increases. Larger surface area = more stoma for water to evaporate out. As temperature increases, transpiration rate increases. Temperature increase = evaporation occurs faster. As wind speed increases, transpiration rate increases. This means water vapour can be removed quickly due to air movement. As the rate of humidity increases, transpiration rate decreases. Evaporation rate decreases due to the high level of water in the atmosphere. 27 a. Blood Content ● Blood is made of: O Red blood cells O O O White blood cells Platelets (for blood clotting) Plasma b. Red Blood Cells Ch.6 Transport systems - Animals Features Plasma O Makes up 55% of the blood O Carries dissolved substance (Example: Protein, soluble end products of digestion & gases) Biconcave shape • Specialised cells used to transport oxygen. They have specialised features to aid their job No nucleus White blood cell Cytoplasm contains haemoglobin Red blood cell plasma White blood cell Side view Function No nucleus so more haemoglobin can fit in Cytoplasm with large amount of haemoglobin Shape gives a large surface area to pass oxygen through Increase surface area so that oxygen can diffuse quicker. Have more space to store haemoglobin. Allows red blood cells to transport a large amount of oxygen once. 28 Haemoglobin equation Haemoglobin c. White blood cells • Phagocytes There are 2 types of white blood cells: o Phagocyte o Lymphocytes • Lymphocytes Oxygen Association (in lungs) O Carry out phagocytosis by engulfing pathogens. o Phagocytes break down and digest pathogens. Dissociation (in tissues) d. Circulatory system O Produce antibody which can destroy pathogens Blue: Deoxygenated blood Red: Oxygenated blood O Each antibody is specific to a pathogen. O Antibodies attach themselves to the target pathogens and attract phagocytes to engulf the pathogen. Oxyhaemoglobin 29 The heart chambers Right atrium Right ventricle Vein that transport blood to the heart Vena Cara Pulmonary artery Left atrium Left ventricle -> Aorta Pulmonary Vein 30 Motion of blood in heart Coronary artery (Coro:nary) Lungs To parts of the Supplies the heart with glucose & oxygen. Waste products are transported by the coronary veins. Coronary arteries Aorta body. 31 e. Blood Vessels Arteries ● Have thick & elastic muscular calls to withstand the high pressure of blood from the heart. ● Have no valves. Vein ● Also allows expansion & contraction of the vessel. ● The largest artery is the aorta. Arteries carry oxygenated blood EXCEPT the pulmonary artery. Carries blood from the heart. ● Thinner muscular wall Thick muscular walls Narrow central channel (lumen) Thinner muscular walls ● Have valves to prevent the backflow of blood. Wider central channel (lumen) Carries blood to the heart. 08 Carries deoxygenated blood EXCEPT the pulmonary vein. 32 Capillaries • Tiny thin walled vessels. All exchanges of materials between blood & tissues takes place through capillary. O Example: Oxygen diffusing from blood to tissue cell • Capillaries form networks, creating a large surface area for exchanging material. Cells forming the capillary wall 33 NOTE: Oxygen and nutrients from food need to be absorbed into the bloodstream so that it can be delivered to cells. This can be done through capillaries. a. Capillary networks ● Have narrow tubes, forming a dense network allowing every cell to be close to the capillary. ● Dense network, large surface area between cells and blood. Ch.7 Absorption of materials • Capillary walls are one cell thick, giving a very short diffusion distance. Factors increasing the rate of absorption: o Large surface area O Thin walls O Extensive blood supply b. Lung & alveoli function & structure Lung Rings of cartilage Ribs Bronchiole Diaphragm- Ka Trachea lung Intercostal muscles Bronchus Alveoli • Rings of cartilage keep the airways open • Diaphragm contracts and relaxes to inhale and exhale air into the lung. Ribs protect the lungs. 34 Alveoli Provide large surface area for gas exchange Thin wall allowing east diffusion of oxygen. Have moist walls, allowing oxygen to dissolve before diffusion. • Capillary around alveoli shorten the distance for diffusion ● Venous blood in Red blood cells- in capillary O CO2 out c. Small intestine structure & function ● In the 1st part of the small intestine, starch 02 in Inner surface contains villi. Air in/out Epithelial cells: Provide a very thin lining Lacteal: Site of absorption of the products of fat digestion (fatty acids and glycerol) Alveoli Factors increasing the rate of absorption in the small intestine o Very long (surface area) O Inner surface is folded Oxygenated blood out glucose & Fat Fatty acid + glycerol. The epithelium covering each villi is thin, therefore allows products to diffuse through quickly. ● Each villus has a network of capillaries for absorbing glucose & amino acid. Each villus also has lacteals for absorbing fatty acid and glycerol. Blood capillary: Site of absorption of the products of starch digestion (glucose) and protein digestion (amino acids) 35 36