Life Processes and Cellular Organization
Big Idea: Living things are organized and carry on life processes (SOL LS.3)
Organisms that are made of only one cell (unicellular) must rely on one cell to do all jobs for the organism. Organisms with more than one cell (multicellular) have cells that do specific jobs. This is called division of labor. Nerve cells send messages as electrical signals; sperm cells play a role in reproduction. A cell in a multicellular organism cannot survive on its own it depends on the other cells in the organism to help the organism carry out all life processes.
Many multicellular organisms are arranged in the following way:
Cells Basic unit; cell organelles do specific Cardiac cells jobs Tissues Groups of similar cells with a specific job Cardiac tissue Organs Groups of tissues with a specific job Heart Organ Systems Groups of organs with a specific job Circulatory system Organism An independent living thing that can Horse perform all life processes
6 What life processes do cells carry out?
1. Growth and division cells increase in size and mass by adding cells (growing) and changing form (developing). Growth and development include repair or replacing old or damaged cells.
2. Cell respiration mitochondria in cells use oxygen to release energy stored in food. Water and carbon dioxide are produced as waste, which leaves the cell.
3. Cell transport materials move in and out of cells through the cell membrane. Cell membranes are selectively permeable; they allow some materials in but not others. Many materials move across the membrane into and out of the cell passively, on their own. When materials move on their own, they naturally move from areas of high concentration to areas of low concentration. Passive movement of water across the membrane by osmosis. Other materials move across the membrane by diffusion.
The blue molecules are moving from where there are many (high concentration) outside the cell across the membrane to inside the cell, where there are fewer (low concentration).
What life processes are carried out by multicellular organisms?
Some life processes are also managed by organs and organ systems in organisms made of many cells.
Respiration: cells exchange the gases carbon dioxide and oxygen, so do organ systems that include lungs or gills or other similar organs. Ingesting food, digesting food, and getting rid of wastes: cells take in and break down food and get rid of wastes, and so do structures in systems such as the mouth, stomach, intestines, and kidneys.
7 Respond to stimuli cells respond to changes in the environment, and so do multicellular organisms such as animals using organs in systems including nerves, brain, and eyes. Plants also respond to changes in gravity, light, and chemicals. Growth, repair, reproduction cells grow and repair themselves, then either die or divide to produce two new cells. Multicellular organisms also grow, repair, and reproduce using egg and sperm produced by ovaries and testes (animals) and flowers (plants).
Cells and entire organisms try to maintain homeostasis (a steady state), so when changes happen in their environment, they respond by adjusting. For example, fish respire (exchange gases) by breathing in oxygen in the water through gills. When water gets colder, oxygen in the water decreases, fish breathe harder to take in more oxygen through their gills. When the water warms, the amount of oxygen increases, and fish e in oxygen through their gills.
8 Test Your Knowledge Big idea: Living things are organized and carry on life processes.
The picture shows several cheek cell
1. What evidence shows these cells are part of a tissue?
2. What is the order of the next three levels that build upon tissues?
3. What is the most basic level of organization?
4. If a cheek cell was surrounded by pure water, would more water move into or out of the cell? Why and by what process would it move?
5. Cell structure is often related to how the cell functions. Explain how the structure of a nerve cell is related to its function and how the structure of muscle cells is related to their function.
9 6. The diagram shows a cross section of a leaf.
a. Identify any three tissues labeled in the diagram.
b. Why are these considered to be tissues?
c. Choose any cell shown and explain how its structure (shape) relates to its job (function).
d. What function do the tissues in this organ work together to do?
e. What is another organ that is a part of this organism?
7. What life processes do an amoeba (a unicellular organism) and a human (a multicellular organism) perform?
10 8. Choose three life processes and compare how they happen in an amoeba and a human. For example, when an amoeba reproduces, it divides to produce two amoebae. When a human reproduces, males produce sex cells (sperm) that unite with sex cells in the female (eggs) to create a new human.
Life Process Amoeba Human
9. Which of these processes takes energy from food? A. Reproduction B. Circulation C. Digestion D. Excretion
10. A sponge is an animal that lives in fresh or salt water. The cells of a sponge perform different functions. For example, as water enters the pores on the sides of the sponge, some cells have long, whip-like structures to move water up and out of the large opening at the top. Sponges trap food that is brought close by the moving water. Their bodies are a loose mass of these and other kinds of cells. Sponges are known as simple animals. Why?
11. Sponges are classified as animals because they A. make their own food B. cannot move from place to place C. cannot get rid of waste products D. catch their own food 11 12. The wilted plant was just watered.
a. By what process did the water move from the soil into the root cells?
b. Is this active or passive transport? Why?
c. Draw a diagram showing water molecules moving from the soil into one root cell. Label and explain your diagram.
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