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Survival and response Aim: To understand the responses animals and plants make in order, to increase their chance of survival What changes in the environment do organisms respond to? Are these responses fast, slow, long or short duration Are these responses chemical or electrical Which chemicals are involved in responses • Hormone – Chemical messages • Neurotransmitters – Chemicals that pass a message from one neurone to another at a synapse • Histamine – Released as a result of infection/injury – causes inflammation due to dilation of blood capillaries- plasma containing antibodies then escapes into the tissue • Prostoglandins – Hormones which help sperm reach the oocyte by causing muscular contractions of the uterus and oviducts Which chemicals are involved in responses • Hormone • Neurotransmitters – 271-272 • Histamine • Prostoglandins Tropisms • Tropisms – A growth movement in response to a directional stimulus • Keeps the roots and shoots in favourable conditions • Plant shoots grow towards light – positive phototrophism • Plant roots grow away from light (negative phototrophism) and towards gravity (positive geotrophism) • Plant roots grow towards water (positive hydrotrophism) TASK Copy and give explain how these keep the roots and shoots in favorouble positions for the plant Auxins • Plant growth is controlled by the growth hormone auxin. The most common type of auxin is IAA. • Task: Using 431 – 432 summarise how scientists discovered how plant growth is regulated Phototrophism Auxins (IAA) Indoleacetic acid • Plant hormone that controls plant growth • Produced in shoot tips • Causes elongation of shoot cells Phototrophism Light destroys auxin - This encourages growth on the shaded side - This makes the shoot bend towards the light Geotrophism • The main plant root always grows downwards towards gravity How geotrophism works • In roots auxin accumulates on the lower side of the root • In roots auxins INHIBIT cell elongation Auxin accumulates Cells continue to elongate Cell elongation inhibited Plant growth factors • The most common growth hormone is IAA Indoleacetic acid (IAA). Pg 157 copy final 3 bullet points and the 2 sentences below it Read application and how science works and answer the questions as you go through Taxes and Kinesis • Responses to stimuli (change in the environment) • Taxes - Directional response to stimulus ie – moves toward (positive taxes) or away (negative taxis to the stimulus • Kinesis – Non directional response to stimulus ie – speeds up, slows down or changes direction more often Task • Plan an investigation into the kinesis response of woodlice to a stimuli • Title • Hypothesis
