How do we define what it means to be alive?

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Kory Leonard
5 years ago
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2 How do we define what it means to be alive?

3 Defining Life There is no universal definition of life. To define life in unequivocal terms is still a challenge for scientists. Conventional definition: must exhibit the following criteria: 1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature. 2. Organization: Being composed of one or more cells, which are the basic units of life. 3. Metabolism: Consumption of energy 4. Growth: A growing organism increases in size in all of its parts, rather than simply accumulating matter. 5. Adaptation: The ability to change over a period of time in response to the environment 6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun or an animal chasing its prey. 7. Reproduction: The ability to produce new organisms.

4 Cell Theory - Review 1. All living things are made of cells 2. Cells are the basic units of structure (form) and function (purpose) in living things. 3. Living cells come only from other living cells Brainpop: Cells

5 What are cells? Cells are the basic unit of structure and function in living things. All living things are made up of cells Cell are the building blocks of life Cells are specialized to do certain jobs in different regions of your body. There 200 different types of cells in your body. Cells are so tiny you could fit more than a million of them on a period at the end of a sentence.

6 What technology was created that allowed cells to be discovered? Hint: you could not SEE a cell without this piece of equipment. Another hint: we used this piece of equipment during our last unit of study.

7 Cells were named by Robert Hooke. 1 st scientist to call spaces in cork cells he observed under the microscope cells. Comes from the Latin word cella which means little rooms. Unicellular: one cell bacteria. Multicellular: many cells humans have over 200 different types of cells (blood, bone, skin) and an estimated 100 trillion total cells.

Cells Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary.

8 Cells Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities. Organelles: small structures, or organs within cells that perform a specific function

9 Cell Membrane Outer structure that surrounds the cell Supports & protects the cell Controls movement of materials in and out of the cell Barrier between cell and its environment

10 Cytoplasm Cell s environment or inner space The jellylike material outside the cell nucleus. Made of mostly water Contains the organelles Site of most cell activity

11 Nucleus The cell s computer, brain, or manager Controls the cell activities Contains all the information the cell needs to do specific jobs, grow, and divide Information is stored in DNA molecules Contains the nucleolus which makes ribosomes Determines what proteins will be made

12 Nuclear Membrane Protects and guards the nucleus Controls movement of materials in and out of the nucleus Keeps the DNA inside the nucleus Allows other materials to pass in and out of the nucleus

13 Ribosomes Makes the proteins the cell needs to survive and grow Produces the Protein which is the Product of the cell

14 Endoplasmic Reticulum (E.R.) The transportation system of the cell Carries material through cell Allows reactions to happen in the cell Where the ribosomes do their work Rough ER has ribosomes attached to it so the proteins they make can be released directly into the ER for transport Smooth ER collects things and contains them

15 Golgi Bodies Packs & carries the proteins Prepares the proteins for use or delivery outside the cell

16 Mitochondria Cell s powerhouse or power generator Supplies the energy Breaks down sugar molecules into energy Need oxygen to make energy and give off carbon dioxide as waste

17 Lysosomes Cell s recyclers Breaks down larger food molecules into smaller molecules Contains enzymes which break down the proteins Digests old cell parts

18 THE DIFFERENCE BETWEEN ANIMAL & PLANT CELLS

19 PLANT AND ANIMAL CELLS

21 CELL WALL: PLANT Function: Gives the cell most of its support and structure A thick, rigid membrane that surrounds a plant cell Bonds with other cell walls to form the structure of the plant

22 Cell Wall Plant cells only Made of cellulose Surrounds the cell membrane Gives plants their shape, structure, and protection Allows H2O, O2, and CO2, to pass in and out of the cell

23 Chloroplast Function: Where photosynthesis takes place An elongated or disc-shaped organelle containing chlorophyll

24 Chloroplasts Plant cells only Power generator for the plant Give plants their green color Uses energy from the sun to make food for the plant through photosynthesis

25 Can you remember the function of each? Cut out the symbols and glue them next to the correct cell part.

27 B. C. A. Cell = City G. D. H. I. E. J. F.

How do we define what it means to be alive?

How do we define what it means to be alive? Defining Life-7 Characteristics of Life There is no universal definition of life. To define life in unequivocal terms is still a challenge for scientists. Conventional