IGCSE Biology - Characteristics of Living Organisms PDF

Edexcel IGCSE Biology 1 - Characteristics of Living Organisms Mrs H. Gren 1  Characteristics of Living Organisms Specification Point 1.1 ○ Understand how living organisms share certain characteristics. All living organisms sha...

Edexcel IGCSE Biology 1 - Characteristics of Living Organisms Mrs H. Gren 1  Characteristics of Living Organisms Specification Point 1.1 ○ Understand how living organisms share certain characteristics. All living organisms share certain characteristics. All eight of these characteristics have to be present to consider an organism as living: ○ Movement. ○ Respiration. ○ Sensitivity. ○ Homeostasis. ○ Growth. ○ Reproduction. ○ Excretion. ○ Nutrition. This is often memorised using the mnemonic Mrs. H Gren. 2  Movement Animals move their entire bodies to get from one place to another. ○ Many animals will move rapidly to get to their prey. Plants can also move their leaves in response to sunlight The cheetah is the world's or their roots in response to fastest land mammal and can reach speeds of up to 70 gravity. mph. ○ This will allow plants to move efficiently photosynthesise. ○ It will also allow plants to reach mineral ions in the soil more 3 easily.  Movement is key to life. The cheetah will move at speeds upwards of 70 mph to catch its prey. 4 Plants move towards light for photosynthesis. 5  Respiration Plants and animals use oxygen from the air to convert glucose into energy. ○ This is referred to as the process of aerobic respiration. This energy is then used for a variety of life processes, including: ○ Movement. ○ Growth. ○ Excretion. ○ Reproduction. There is an equation for aerobic respiration: OXYGEN + GLUCOSE → CARBON DIOXIDE + WATER + ENERGY 6  Respiration releases energy which is used for a variety of other metabolic processes. 7  Sensitivity All living things respond to changes. ○ These changes are referred to as stimuli. Living things have the capability to detect these changes through receptors. ○ Plants notice changes in season. ○ Animals notice changes in temperature The human hand contains and pressure. millions of receptors in These organisms then react the fingertips which can detect different stimuli. accordingly. ○ Plants may lose their leaves when the weather gets colder. 8 ○ Animals may change their internal  Homeostasis Sometimes referred to in textbooks as control, this is the ability to regulate the internal conditions of the body. ○ Animals have a nervous system and a hormonal system which allows for coordinated responses. ○ Some plants have hormone-like chemicals which work in the same way. Many hormones that are important for homeostasis Homeostasis ensures that conditions in are produced in glands found the body remain constant. in the brain. ○ This ensures that molecules like enzymes can work as efficiently as possible. 9  Growth Growth is an increase of cell size, cell number or cell complexity. ○ Babies grow into infants, infants into adolescents and adolescents into adults. ○ In botany, seedlings grow into plants. Growth is important as it increases the likelihood of survival. ○ An adult animal for example is more able to defend itself against attack than an infant. It takes approximately 20 years for a human to fully develop into an adult. 10 As plants grow their stems will get longer. 11  Reproduction All living organisms reproduce. Animals either use sexual or asexual reproduction to produce offspring ○ Mammals reproduce sexually. ○ Some animals (mostly amphibians) and all bacteria reproduce asexually. Plants use pollination or self- fertilization to produce offspring. Reproduction ensures that a species Many plants use does not become extinct. pollinators like bees ○ The survivability of a species is ensured to fertilise and through reproduction. reproduce. 12 Bacteria reproduce by a kind of asexual reproduction referred to as binary fission. 13  Excretion As a consequence of metabolic processes, the body will build up waste chemicals. These have to be removed from the body to prevent toxic build-up: ○ Both plants and animals have mechanisms to accomplish this. The kidneys are an The kidneys in mammals and the important excretory organ stomata in plants are good examples of that filter toxins out of the bloodstream. excretory organs. ○ The kidneys remove excess urea in the form of urine. ○ The stomata remove excess oxygen from 14  Nutrition Energy is needed for growth and repair of the body. ○ A growing organism will require energy to develop new cells. ○ Cells can also become damaged or can wear out over time. ○ Energy is used to repair or replace these cells. Nutrients (food) are used to provide this energy: ○ Animals derive energy from eating. Many animals are This is referred to as heterotrophy. part of nutrient Some eat other animals (carnivores), some food chains. eat plants (herbivores). ○ Plants create their own food source using 15 Humans should eat a balanced diet of fruit and vegetables for optimum nutrition. 16