Living Things and How are living things classified?

1. Living ThingsandHow are living things classified?

2. What are living things like? • Any living thing is called an organism. • Organisms • vary in size • are found just about everywhere • have different behaviors and food needs. • However, all organisms have similar traitsthat determine what it means to be alive.

3. How are living things organized? • Living things are made up of small units called cells. cell : is the smallest unit of an organism that carries on the functions of life. • Some organisms are made up of just one cell, others are made up of many cells. • Cells take in materials from their surroundings. • Each cell has an orderly structure and has hereditary material. • All the things organisms can do are possible because of what their cells can do.

4. How do living things respond? Living things interact with their surroundings. Anything that causes some change in an organism is a stimulus (plural, stimuli). The reaction to a stimulus is a response. Often that response results in movement.

5. Response to Stimuli To carry on its daily activity and to survive, an organism must respond to stimuli. Organisms respond to external stimuli such as movement and light. Living things also respond to stimuli that occur inside them. The organisms then make internal changes to keep the right amounts of water and food in their cells. An organism’s ability to keep the proper conditions inside no matter what is going on outside the organism is called homeostasis.

6. How do living things grow and develop? • Organisms grow by taking in raw materials. • One-celled organisms grow by increasing in size. • Most growth in many celled organisms is due to an increase in the number of cells. • Organisms change as they grow. • All of the changes that take place during an organism’s life are called development. • Complete development can take a few days for the butterfly shown below, or several years for a dog. • The length of time an organism is expected to live is its life span. • Some organisms have a short life span. Some have long life spans.

7. Why do living things reproduce? • Organisms eventually reproduce. • They make more of their own kind. • Some bacteria reproduce every 20 minutes. • A pine tree might take two years to produce seeds. • Without reproduction, living things would not exist to replace those individuals that die.

8. What raw materials do organisms need? • Water is important for all living things. • Most organisms are made of more than 50 percent water. • Humans are made of 60 to 70 percent water. • Plants and animals take in and give off large amounts of water each day. • Organisms use homeostasis to balance the amount of water taken in and lost.

9. What raw materials do organisms need? • Organisms use water for many things. Blood is about 90 percent water. • Blood transports food and wastes in animals. • Plants use water to transport materials between roots and leaves.

10. What raw materials do organisms need? • Living things are made up of substances such as sugars, proteins, and fats. • Animals get these substances from the food they eat. • Plants and some bacteria make the substances using raw materials from their surroundings. • These important substances are used over and over again. • When organisms die, substances from their bodies are broken down and released into the soil or air. • The substances can then be used again by other organisms.

11. Classification • When similar items are placed together, they are being classified. • Organisms also are classified into groups. • Early classifications of organisms included grouping plants that were used in medicines. • Animals were often classified by human traits. • For example, lions were classified as courageous animals and owls were classified as wise

12. Classification • More than two thousand years ago, Aristotle, a Greek, decided that any organism could be classified as either a plant or an animal. • Then he broke these two groups into smaller groups. • For example, his groups included animals that had hair and animals that did not have hair, and animals with and without blood.

13. Who was Carolus Linnaeus? • In the late 1700s, Carolus Linnaeus, a Swedish naturalist, developed a new system of grouping organisms. • His system was based on organisms with similar structures. • For example, plants that had a similar flower structure were grouped together. • His system was accepted and used by most other scientists.

14. What classification do modern scientists use? • Modern scientists • use similarities in structure to classify organisms • use similarities in both external and internal features. • For example, scientists use the number of chromosomes in cells to understand which organisms may be genetically related to each other • study fossils, hereditary information, and early stages of development. • Scientists use the information to determine an organism’s phylogeny. • Phylogeny (fi LAH juh nee) is the organism’s evolutionary history. • This tells how the organism has changed over time. • It is the basis for the classification of many organisms.

15. How are organisms grouped? • A classification system commonly used today groups organisms into six kingdoms. • A kingdom • first and largest category • divided into smaller groups. • the smallest classification is a species. • Organisms in the same species can mate and produce fertile offspring.

16. Scientific Names • If scientists used only common names of organisms, it would be confusing. • For example, a jellyfish is neither a fish nor jelly. • A sea lion is more closely related to a seal than a lion. • To avoid confusion, scientists use a naming system developed by Linnaeus when referring to a particular species. • Each species has a unique, two-word scientific name.

17. What is binomial nomenclature? • The two-word naming system used to name organisms is called binomial nomenclature (bi NOH meeul · • NOH munklaychur). • The first word of the two-word name identifies the genus of the organism. • A genus is a group of similar species. • The second word of the name might tell you something about the organism. • It might tell what it looks like or where it is found.

18. Why are scientific names used? • Two-word scientific names are used for four reasons. • They help avoid mistakes. • Animals with similar evolutionary history are classified together. • Scientific names give descriptive information about the species. • Scientific names allow information about organisms to be organized easily and efficiently.

19. Tools for Identifying Organisms • Tools used to identify organisms include field guides and dichotomous (di KAH tuhmus) keys. • Field guides include • descriptions and pictures of organisms • give information about where each organism lives • to identify species from around the world.

20. What are dichotomous keys? • A dichotomous key is a detailed list of identifying characteristics that includes scientific names. • The keys are set up in steps. • Each step has two descriptive statements, such as hair or no hair. • You can use a dichotomous key to identify and name a species.