Cells Reproduction and Inheritance

Transcription

1 S2 Biology 3 Cells Reproduction and Inheritance Cells Cells are the tiny building blocks that make up all living things. Living things can be unicellular or multicellular. Unicellular = organism made of only 1 cell_ Multicellular = organism made of multiple/many cells Cells are measured in µm. 1mm = _1000_ µm The Microscope See PPoint for completed diagram Lens Colour Eyepiece Magnification Small Medium Long Lens Magnification Total Magnification 1 P a g e

2 Objects viewed under a microscope look much bigger but they also look slightly different to the actual object. The letter P as it looks on the slide: P The letter P as you look down the eyepiece lens: P Magnification = x Describe the 2 differences: 1. Upside down 2. back to front Make up more slides to view and draw what you see below, remember to note the object and the magnification used. 2 P a g e

3 Examining Cells Animal Cell Plant Cell Bacterial Cell Yeast Cell X X X X In order to be able to view cells under a microscope a stain must be added. Cell Type Stain Used Colour of Stain Animal methylene blue blue Plant iodine orange/brown Bacteria nigrosin black Yeast methylene blue blue Cell Structure plant_ Cell animal Cell yeast Cell bacterial Cell 3 P a g e

4 Cell Parts and Functions Cell Part Function Found in Nucleus contains genetic information Plant Yeast Animal Cell Membrane Cytoplasm Cell wall allows substances to pass into and out of the cell site of chemical reactions holds plant cell shape/structure Plant Yeast Animal Bacterial Plant Yeast Animal Bacterial Plant Yeast Bacterial Chloroplast site of photosynthesis Plant Vacuole contains dissolved sugars/salts Plant Yeast Plasmid contains genetic information Bacterial 4 P a g e

5 Specialised Cells There are many different types of animal and plant cell. They are called specialised cells and all have very different jobs. Although all animal cells and all plant cells have the same basic parts, they can have special features that make them good at their job. Specialised Cell Red blood cell Leaf palisade cell Nerve cell Root hair cell Plant or Animal? Diagram Function How structure makes it good at its job animal carry oxygen Biconcave shape increases surface area No nucleus more space for oxygen Haemoglobin carries oxygen plant photosynthesis has lots of chloroplasts for photosynthesis large surface area to maximise light absorption animal carry electrical messages long and thin to carry messages all around body insulated for quick transfer of electrical messages plant absorbs water large surface area maximises water absorption Specialised Cells for Reproduction In order for animals to reproduce, they must produce specialised cells called sperm and eggs. These specialised cells are known as sex cells or gametes. 5 P a g e

6 Male gamete = sperm Female gamete = egg The Sperm Cell The Egg Cell Diagram Site of production testes ovary Size very small larger Number half a billion 1500 per second one per month Mobility tail to swim cannot move independently Fertilisation Fertilisation is when the nucleus of an egg cell fuses with the nucleus_ of a sperm cell. Site of fertilisation = oviduct_ 6 P a g e

7 Only 1 sperm can fertilise an egg cell. The sperm cell has _50_ % of the genetic information in its nucleus The egg cell has 50_ % of the genetic information in its nucleus 7 P a g e

8 See PPoint for completed diagrams 8 P a g e

9 Embryo Development Stages of Fertilisation See PPoint for completed diagram After fertilisation the tiny ball of cells implants into the wall of the uterus and begins to develop. 9 P a g e

10 Developing Embryo Size _o.1mm_ Important developments: Cells divide and becomes a blastocyct. Moves along oviduct Size mm Important developments: Cells implant into uterus lining Size 3mm Important developments: arms and legs grow longer. Lungs begin to develop Size 16cm Important developments: baby can hear, swallow and move around Size 50cm Important developments: head hair coarse, fingernails longer 10 P a g e

11 Average weight of baby at birth (g) Effect of Chemicals on Developing Embryos Chemicals like tobacco and alcohol can have effect the growth and development of an embryo. Complete the graph below to show the effect of smoking on an unborn baby Smoking Status of Mother Average weight of baby at birth (g) Non smoker 340 Smoker who gave up before pregnancy 335 Smoker throughout pregnancy Describe the effect of smoking on the average weight of babies at birth. Smoking decreases the average birth weight of babies 11 P a g e

12 Inheritance Genetic information is passed on from parents to their offspring (children) through genes found on DNA. This happens during fertilisation. Information about characteristics like hair colour, height, blood type and eye colour are all passed on by parents. This is called inheritance. The characteristics we can see in an organism is called its phenotype. My phenotype For every characteristic we have, we receive 2 copies of the gene that controls this. One copy from mum and the other from dad. Inheriting Eye Colour The gene for eye colour can take many different forms, blue, green, brown, hazel etc. Mum X Dad Blue eyes Brown eyes Child The child has received one gene for blue eyes from dad and one gene for brown eyes from mum. The child s eyes will be brown The dominant gene for eye colour is brown Dominant traits are always shown in the organisms phenotype. 12 P a g e

13 Characteristics and Identification of Organisms An organism s phenotype can help it to be identified. Scientists use keys for identification. Branching Keys A branching key is a diagram with questions that you answer and follow to identify the organisms within it. Yes Do its wings join at the bottom? Mike Scott Betsy Tom Paula Fred Use the key to identify the 2 organisms below: 6 legs Paula Tom 13 P a g e

14 DNA Structure and Function DNA a like special code that is found on chromosomes in the nucleus of cells. In bacteria, the plasmid is made of DNA. It contains many regions called genes that control an organisms characteristics. Each gene tells your body how to make a particular protein. DNA Profiling DNA profiling is when the special code on a person s DNA is collected and analysed. It can be used for many different reasons. Uses of DNA DNA is unique so no one s DNA is the same. This makes DNA very useful for identifying certain individuals. DNA Use Description of Use Advantages Disadvantages Forensics Paternity Testing DNA sequences can be collected as evidence from crime scenes and can be compared with DNA from victims and suspects to find a match DNA from parents and children can be sequenced and compared to look for similarities Identifies criminals Time consuming, criminal s DNA must be on record in order to be found a match Identifies biological parents of children Someone might not realise that their parents are not in fact their biological parents so could be upsetting to find out Disease Detection DNA of individuals can be sequenced and checked for sequences that cause/could cause certain inherited diseases Can allow people to prepare for illness or disease/can help future and family planning/allows people to take preventative measures Some people might not want to know if they are going to develop a disease/might affect life insurance or mortgages 14 P a g e

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