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Variation and Genes

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Variation and Genes Variation • These dogs belong to the same species, just as we all belong to the same species • However, there can be lots of differences between members of the same species (as we saw with the poodle and the labrador )   These differences within a species are called variation There are two factors which cause variation: The characteristics you inherit from your parents AND The environment in which you live • Some characteristics can be both inherited and environmental , for example: HEIGHT Height is mostly determined by inheritance, but there are environmental factors such   as a poor diet which can stunt growth. In fact, there are only FOUR factors which are not influenced at all by environmental factors.These are eye color, natural hair color, Blood groups i.e A,B,O and AB. How do we inherit characteristic ? In our body, there are 23 pairs of chromosomes (so 46 altogether!) • Egg ...
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Evolution and Survival of the Fittest

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Evolution and Survival of the Fittest Must watch this  https://www.youtube.com/watch?v=vnktXHBvE8s  Charles Darwin- The theory of Natural selection Must watch this  https://www.youtube.com/watch?v=7VM9YxmULuo  Natural selection What is Evolution? • Evolution is the gradual change of an organism over time. What is Natural Selection?   This is when organisms that are better adapted are “selected” to survive. e.g. the rabbit that is more muscular and so can run away from a fox faster is more likely to survive. How does Evolution Happen? Evolution happens due to a process known as NATURAL SELECTION (where nature selects certain organisms to survive). Natural selection happens because all individuals in a population show variation (differences) due to mutations (changes) in the organisms genes.  Some organisms within the population will be better adapted to survive because they are better at: • Finding a mate • ...
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RESPIRATION

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RESPIRATION TYPES OF RESPIRATION There are 2 types of respiration: • Aerobic respiration • Anaerobic respiration WHAT IS RESPIRATION? • Respiration is a chemical reaction that takes place in the mitochondria of all cells. • This chemical reaction releases energy in the form of a molecule called ATP Organisms need energy: • To power the chemical reactions needed to keep us alive, e.g. building large molecules. • For movement (both within the organism and contraction of muscles) • For keeping warm. ORGANISMS ALSO NEED ENERGY FOR: • Cell division • To maintain a constant environment in our bodies • For active transport • To send nerve impulses AEROBIC RESPIRATION • When respiration uses oxygen it is called AEROBIC RESPIRATION. • It is an exothermic reaction which means that it gives out heat. • Any energy that is not used to create ATP (energy store) is released as heat • Remember that any living organism has to carry out respiration therefo...
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The Menstrual Cycle

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The Menstrual Cycle Hormones Four hormones involved in controlling menstruation.   FSH Oestrogen LH Progesterone FSH (follicle stimulating hormone) and LH ( Luteinising hormone) these hormones are released from pituitary gland in the brain. They help to control the mestural cycle. Function of FSH is stimulates one egg cell to develop and stimulates the ovaries to produce oestrogen. Function of LH  is stimulate the release of an egg at day 14 (ovulation).  Oestrogen Causes the lining of the uterus to thicken and grow. Stimulates the production of LH. Inhibits the production of FSH so that only one egg is released in each cycle.  Progesterone Maintains the lining of the uterus. when the level of progesterone falls and there's a low oestrogen level, the lining breaks down. Inhibits the production of FSH and LH. A low progesterone level allows FSH to increase and then the whole cycle starts again. The Cycle The mestrual cycle has f...
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Photosynthesis

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PHOTOSYNTHESIS Photosynthesis is a series of 2 reactions that can be summarised using the following equation:   Carbon Dioxide + Water =====>   Glucose + Oxygen   6CO2  +  6H2O ===> C6H12O6 + 6O2 • The first reaction only happens when light energy is present and the second reactions can happen without sunlight. • As photosynthesis reactions need sunlight energy, the reactions are said to be ENDOTHERMIC . PHOTOSYNTHESIS AND CHLOROPLASTS • Photosynthesis happens in organelles called Chloroplasts which contain a green substance called chlorophyll . • Chlorophyll absorbs sunlight energy so that photosynthesis can happen. This means that any part of a plant that is green will contain chloroplasts and so produce sugars like GLUCOSE and SUCROSE through photosynthesis. Only plants have the ability to transfer light energy into chemical energy so they are called PRODUCERS and are the source of all energy on the planet...
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Movement of water through plants (Xylem)

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Movement of water through plants  (Xylem) ARRANGEMENT OF XYLEM IN ROOTS ARRANGEMENT OF XYLEM IN STEMS ARRANGEMENT OF XYLEM IN LEAVES ROOT HAIR CELLS INCREASE SURFACE AREA The increased surface area means that water can be absorbed faster from the soil. TRANSPIRATION Transpiration is the loss of water vapour from leaves which causes water molecules to be pulled upwards through the roots, stem and leaves. The water is needed for photosynthesis and to keep plant cells turgid (full) which supports the plant and prevents it from wilting.  WHAT HAPPENS IF A PLANT DOES NOT HAVE ENOUGH WATER? • The plant wilts as the cells are no longer turgid. • As cells are not turgid stomata close to prevent further water loss. • The drooping leaves reduces their surface area which helps to reduce water loss. • Plants may overheat when they do not have enough water. • Plants will stay wilted until they receive enough water. http...
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DNA

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DNA STRUCTURE OF DNA • DNA is structured like a ladder that has been twisted. • We call this shape  double helix. • It is made from repeating units called NUCLEOTIDE, which makes DNA and POLYMER. STRUCTURE OF  NUCLEOTIDE Each nucleotide is made from 3 parts: • Sugar (deoxyribose) • Phosphate • Base • The sugar and the phosphate make the 2 sides of the ladder. • The bases make the steps of the ladder. THE BASES IN DNA There are 4 different bases in DNA: • A - Adenine • T - Thymine • C - Cytosine • G – Guanine It is the bases that make up the human genetic code. There are roughly 3.3 billion base pairs in our genetic code. Genes vary in length from a few hundred bases to more than 2 million. THE GENETIC CODE   Bases always pair up in the same way creating 2 strands (each side of the ladder) The 2 strands are said to be COMPLEMENTARY. How do the bases pair up?  https://www.youtube.com/watch?v=...
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