We all have these in common.

8 Characteristics of Life

Living things share 8 characteristics:

1. Living things are made up of units called cells.

a. Every organism is composed of at least one cell.

1.) single-celled or unicellular

2.) many-celled or multicellular

b. There are two broad categories of cells:1) prokaryotic—no organized nucleus nor

membrane bound organelles; found in bacteria and cyanobacteria

2) eukaryotic—do have an organized nucleus and membrane-bound organelles such as Golgi apparatus and mitochondria. All other organisms such as plants and animals have this kind of cell.

2. Living things reproduce. There are two basic kinds of reproduction:

a) Asexual—only one parent and all offspring are identical; for example, binary fission of bacteria or amoebas.

b) Sexual—two cells from different parents unite to produce the first cell of a new organism.

3. Living things are based on a universal genetic code (DNA).

a) The directions for inheritance are found in deoxyribonucleic acid or DNA.

b) The genetic code is basically the same for all organisms on Earth.

4. Living things grow and develop.a) For single-celled organisms, growth is

mostly an increase in size.b) Multicellular organisms go through a

process called development, where cells divide and differentiate into different kinds of cells.

5. Living things obtain and use materials and energy.

a) The combination of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes is called metabolism.

b) Autotrophs (also called producers)—plants, most algae, and some bacteria obtain their energy directly from the sun through photosynthesis.

c) Heterotrophs (also called consumers)—most other organisms, rely on the energy stored during photosynthesis.1. Herbivores—eat plants and other photosynthesizing

organisms2. Carnivores—eat the herbivores or other carnivores3. Omnivores—eat both plants and animals4. Decomposers—such as bacteria and fungi; obtain

energy from the remains of organisms that have died

6. Living things respond to their environment.a) Organisms detect and

respond to stimuli from their environment.

b) A stimulus is a signal to which an organism responds.

c) External stimuli include temperature and light.

d) Internal stimuli come from within, such as blood sugar level or feeling thirsty.

7. Living things maintain a stable internal environment.

a) Even though external environmental conditions may vary widely, most organisms must keep internal conditions, such as temperature and water content, fairly constant.

b) Maintaining a stable internal environment is called homeostasis (Greek, same condition).

8. Taken as a group, living things change over time (living things evolve).a) Plants have adapted to living in dry and hot

deserts.b) Fossils of ancient organisms can be used to

show how organisms have changed over time.

Levels of Organization1. Organism

2. Organ System

3. Organ

4. Tissue

5. Cell

Cell Structure and Function Notes

Discovery of the Cell: • Mid 1600’s scientists began using

microscopes to observe living things

• Robert Hooke used microscope to observe thin slice of cork—dead plant materialCork seemed to be made of box-like chambers—Hooke called cells

• Anton van Leeuwenhoek discovered living cells in pond water

Cell Theory:• All living things composed of cells

• Cells are the basic unit of structure and function in living things

• New cells are produced from existing cells

Cell and its Environment:

• Organisms made of one cell—unicellular organisms

Ex: bacteria

• Organisms made of many cells—multicellular organisms

Ex: plants, animals

• Each cell must be in “balance” with its environment, exchange food, waste, H2O, CO2, O2 etc.

• Process by which organisms maintain a relatively stable internal environment—homeostasis

Cell:

• Organisms that do not have a distinct nucleus—prokaryotic (PRO = NO)

Ex: bacteria

• Organisms with cells that have true nucleus and organelles—eukaryotic (EU = TRUE)

Ex: plants, animals, fungi

Cell Parts and Their Functions:

Specialized cell parts called organelles—“little organs”

1. Cell membrane—determines what goes in and out of the cell

2. Cytoplasm—gel-like medium that holds the organelles in position

3. Nucleus—control center of the cell• Double membrane that surrounds the nucleus—

nuclear membrane

• Hereditary information inside the nucleus—chromatin (DNA)

4. Ribosomes—makes proteins

5. Rough Endoplasmic Reticulum (rough ER)— makes and transports proteins within the cell

• Called rough ER because of the ribosomes found on its surface

6. Smooth Endoplasmic Reticulum (smooth ER)—makes and transport lipids and other materials within the cell

• Called smooth ER because no ribosomes found on its surface

7. Cytoskeleton—network of protein filaments that helps cell maintain its shape

8. Golgi apparatus—processes and packages proteins and other substances produced in the ER

9. Mitochondria—energy source of the cell (powerhouse)

10. Vacuoles—sac-like structures for storage

• Plant cells usually contain a large vacuole that fills most of the cell—pressure from this large vacuole helps plants support themselves

Found in animal cells only:

11. Lysosomes—cleans up the cell and digests unwanted materials

Found in plant cells only:12. Cell wall—provides support and

protection for cell• Composed mainly of cellulose (plant starch)—

fiber for our diet

13. Chloroplast—makes glucose using the energy from the sun (photosynthesis)

Specialized Parts for movement:

1. Cilia (like little hairs) 2. Flagella (like a tail)

Specialized Cells:Different cells in your body do different jobs. The structure (how it’s built) of cells matches the function (what it does).

• Plant Examples:

1. Leaf cell—contains many chloroplasts to maximize photosynthesis

2. Root cell (potato)—contains many vacuoles to maximize water and starch storage

• Animal Examples:1. Epithelial cells—have villi to

increase nutrient absorption; found in the intestines

2. Muscle cells—contain many mitochondria to produce more energy for movement

3. Nerve cells—have fibers called dendrites that allow nerve cells to communicate

with each other