The Characteristics of Life.docx

The Characteristics of Life Life describes an organism which shows metabolism and continuity of life. **Need to know Definition** Life Is a state that differentiates plants, animals, and microorganisms from inorganic matter, such as rocks and water. Life includes the capacity for growth, reproductio...

The Characteristics of Life Life describes an organism which shows metabolism and continuity of life. **Need to know Definition** Life Is a state that differentiates plants, animals, and microorganisms from inorganic matter, such as rocks and water. Life includes the capacity for growth, reproduction, functional activity, and continual change. Due to the varied and complex nature of the organisms that we deem to be ‘alive’, a one-sentence definition of life that covers all of them is not possible. There are a certain number of features and behaviours that all living things have in common. Non-living things may have one or two of these features, but only living things have all of them. Metabolism is the sum of all the chemical reactions in an organism. There are two types of metabolism: 1. Catabolic – Reactions that involve the breakdown of large substances to smaller ones, e.g., digestion and respiration. 2. Anabolic- Reactions that involve smaller molecules being used to make larger molecules e.g., photosynthesis, synthesis of proteins and DNA, the use of illegal anabolic steroids to build up muscle and bone. Continuity of life describes how living organisms arise from living organisms of the same type. **Need to know definitions for both types of Metabolism and Continuity of life** Characteristics of Life **Need to know 5 characteristics and be able to describe them** The cell is the smallest entity that has all the characteristics of Life. Organisation - The ordered way in which living things are arranged structurally. All living things are made of cells. Some consist of one cell (unicellular) e.g., bacteria and amoeba, others multicellular e.g., humans. All organisms carry out their activities in cells. This gives a structured plan to improve efficiency and increase the chances of survival. (1) Molecules Groups of Atoms that are chemically joined. For example, DNA, Water, Glucose Organelles Very large groups of different molecules which carry out functions. For example, nuclei, mitochondria, ribosomes, chloroplasts Cells Basic Unit of living things. Consist of Organelles suspended in a fluid called cytosol surrounded by a cell membrane. Tissues Groups of similar cells working together to carry out a function. For example, muscles, nerves, and connective tissue in animals. Xylem, phloem, and mesophyll in plants. Organs Groups of different tissues working together to carry out a function. For example, lungs, skin, and heart in animals. Root, stem, leaf, and flower in plants. Organ Systems A group of organs that work together to carry out a function. Circulatory system and Nervous system. Organisms Individual living entities ranging in complexity from unicellular examples such as bacteria and algae to complex flowering plants and mammals. Populations Groups of individuals of the same species living together and interacting with each other and the environment. Communities Groups of different species interacting with each other in an ecosystem. Ecosystems Plants, animals, and microorganisms interacting with each other and their environment. Biosphere All the parts of the earth where life exists. For example, air, water, land and underground. Nutrition - Nutrition is the way organisms obtain and use food. Food is needed as a source of materials and energy. Plants and some bacteria are autotrophic i.e., they make their own food. Animals, fungi, and most bacteria are heterotrophic i.e., they must consume food which is made by plants. (2) Excretion - Excretion is the removal of waste products of metabolism e.g., urea and carbon dioxide from the body. These waste products can become toxic to the cell if allowed to accumulate. The organism tries to maintain a constant internal environment (homeostasis). Plants have less need for excretion because they make their own food and do not produce or take in as much waste (stomata used for waste gases). Advanced animals transfer waste internally from cells to blood to excretory organs e.g., lungs, skin, urinary system. The Liver breaks down toxic material. Responsiveness - The reaction of organisms to stimuli in their environment. Animals use their muscles and glands to respond to stimuli such as light, temperature., pressure, and sound (5 senses). Animals tend to move to find food mainly and to avoid danger. Movement in plants is not so obvious. Plants show growth tropisms e.g., respond to light (e.g., stem bends towards light), water, gravity, chemicals, temperature, and touch. (3) Reproduction – The ability of an organism to make new organisms of the same type. There are two types of reproduction; a. Sexual Reproduction – Involves the production and fusion of gametes, one of which is often referred to as male, while the other is referred to as female. It is the preferred method of reproduction in advanced organisms and leads to variation, which allows evolution. b. Asexual Reproduction – The most common in primitive organisms such as bacteria and amoebae. It only involves one parent, and it produces offspring that are identical to the parent. Some advanced organisms use both sexual and asexual reproduction. These are mainly plants, but starfish, bees and greenfly reproduce using both forms, depending on circumstances. References 123rf.com Wikipedia.com Sarthaks.com