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#biology #organisms #mrsgren • Movement: an action by an organism or part of an organism causing a change of position or place. • Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism. • Sensitivity: the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses. • Growth: a permanent increase in size and dry mass by an increase in cell number or cell size or both. • Reproduction: the processes that make more of the same kind of organism. • Excretion: the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements. • Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds, ions and usually need water. MRS. GREN • Movement. • Respiration. • Sensitivity. • Growth and development. • Reproduction. • Excretion. • Nutrition.

#Mitosis #Inheritance #Biology Mitosis - Basics • Most body cells have two copies of each chromosome • We describe these cells as diploid • When cells divide their chromosomes double beforehand • This ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid) • This type of cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction and is known as mitosis • Mitosis is defined as nuclear division giving rise to genetically identical cells  Process: • Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x - shaped chromosomes) • Chromosomes line up along the centre of the cell where cell fibers pull them apart • The cell divides into two; each new cell has a copy of each of the chromosomes Importance: • All cells in the body (excluding gametes) are produced by mitosis of the zygote • Mitosis is important for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo) Occurs in: • Growth: mitosis produces new cells • Repair: to replace damaged or dead cells • Asexual reproduction: mitosis produces offspring that are genetically identical to the parent Mitosis & Stem Cells • Many tissues in the human body contain a small number of unspecialised cells • These are called stem cells and their function is to divide by mitosis and produce new daughter cells that can become specialised within the tissue and be used for different functions • The ultimate stem cell is the zygote • A zygote divides several times by mitosis to become a ball of unspecialised cells (around 200-300 cells) • These are embryonic stem cells • These cells are all the same and start differentiating as the fetus develops with recognisable features

water pollution occurs when energy and other materials are released into the water, contaminating the quality of it for other users. Types Surface water pollution Found on the exterior of the Earth's crust , oceans, rivers and lakes . Groundwater pollution Found in soil or under rock structure or aquifers . Different causes of water pollution Marine dumping Industrial waste Sewage , mainly from households . Nuclear waste Oil pollution Underground storage leaks. Effects on environment Toxic water Thermal heating Our sources of water