Growth and Development B5 Revision Growth and Development An accelerated revision resource A.Blackford

WARNING Revision IS important This PowerPoint is not a substitute for active revision using notes, the workbook and revision guide. You also need to do plenty of past papers to get exam practice. Good luck!

Growing and Changing Cells Tissues Organs Systems Organisms We develop as we grow older Larger animals and plants are built of specialist cells arranged in particular ways You need to be able to name examples in each category for animals and plants Cells Tissues Organs Systems Organisms Red blood cells Nerve cells Palisade cells Xylem cells Phloem cells Xylem tissues Muscle tissue Nervous tissue Blood Flower Biceps muscle Eye Leaf Root Lungs Root system Respiratory Skeletal Nervous Digestive reproductive Buttercup House fly Human Cat Dolphin Earthworm Oak tree

Single Cell to Fully Grown Human fertilised egg cells are called ZYGOTES After 10 days the zygote has 100 cells After 2 months the major organs have formed An adult human has about 1014 cells In plants, growth is at the tips of roots and shoots in areas called MERISTEMS. There are also meristems to make the stems thicker and in side buds for when they grow

Growing Back Plant meristem cells are unspecialised and can continue to grow throughout the plants lifetime. Newts have spare unspecialised stem cells to allow them to grow back damaged or lost parts. Human stem cells are specialised e.g. for skin. Plants can be grown by using their meristems e.g. from cuttings. These are dipped in hormone rooting powder containing AUXINS to aid root growth. The new plants are clones.

Nucleus Revision DNA Humans have 46 chromosomes (23 pairs one set from mother one set from father) Human sex cells have 23 chromosomes Humans have about 30 000 genes Genes code for PROTEINS DNA can make an exact copy of itself Human red blood cells have no nucleus

Mitosis – For growth and repair Interphase DNA divides Cell grows Organelles divide I Prefer My Aardvark Toasted Prophase Chromosomes has identical copy attached to it Chromosomes become visible Metaphase Chromosomes line up in the equator Anaphase Chromosome copies separate Copies move to opposite ends of the cell Telophase New nuclear membranes form Cytoplasm divides 2 identical cells produced (also identical to parent cell)

Sexual Reproduction Involves the fusion of male and female gametes (sex cells) From any individual, no two gametes are the same. The chromosomes they have are a mixture of maternal and paternal ones Gametes have HALF the number of chromosomes that the rest of the body has Gametes are made by MEIOSIS which halves the number of chromosomes.

DNA Structure It has a DOUBLE HELIX structure There are 4 bases that always pair up in the same way (base pairing) Adenosine (A) with Thymine (T) Guanine (G) with Cytosine (C) It can make an exact copy of itself Weak bonds between the bases split A new strand starts to form on the free bases

Making Proteins Proteins are made up of amino acids There are about 20 possible amino acids to use 3 bases on the DNA code for a single amino acid (triplet code) mRNA forms on the untwisted DNA mRNA has Uracil (U) instead of thymine (T) mRNA moves out of the nucleus through pores Ribosomes attach to one end of the mRNA and as they move along amino acids are added to make up the protein

Specialised Proteins Protein Found in Property Strong and insoluble We have around 300 different specialised cells Genes are lengths of DNA and they make proteins Antibodies Protein Found in Property Strong and insoluble Keratin Nails, hair skin Skin Elastin Springy Tough but not very stretchy Skin Collagen Speed up chemical reactions Enzymes All cells, the gut Defend against disease Antibodies In the blood

Gene Switching The one-gene-one-protein theory 25 000 – 30 000 genes in humans In stem cells all these genes are switched on As some cells specialise some are switched off In the mammalian egg cells proteins are unevenly distributed therefore one part will become the head and the other the tail

Stem Cells Stem cells produced could be used to treat heart disease, diabetes, Parkinson’s and lots more

Phototropism Plant stems will grow towards the light. This is PHOTOTROPISM Plants grown in normal light. Green and sturdy Plants growing towards the light Plants grown in the dark. They are CHLOROTIC (yellow) and spindly (ETIOLATED

Auxins at Work LIGHT LIGHT LIGHT Conclusion Auxin is produced by the tip of the oat seedling More auxin goes to the dark side Auxin makes the cells grow faster