6.5 - Multicellular Organisms Meeting Their Needs

Question 1

Give an example of how systems work together.

Answer 1

For example, oxygen and nutrients are materials that cells need to survive. Th e respiratory, digestive, and circulatory systems work together to meet this need. The respiratory system supplies oxygen to blood cells and the digestive system supplies nutrients. The circulatory system then pumps the oxygen- and nutrient-rich blood to all the cells of the body. Cells use the nutrients and oxygen to produce energy. During this process, cells release carbon dioxide as a waste product. The carbon dioxide diffuses out of the cells of the body and into blood cells. The blood cells are then transported to the lungs by the circulatory system, where carbon dioxide can be exhaled from the body.

Question 2

How do some organ systems affect the others?

Answer 2

An organism is only as strong as its weakest system. For example, the circulatory system depends on at least two other organ systems (respiratory and digestive systems) in order to do its job properly. If one of these organ systems is not doing its job well, the whole organism can be affected.

Question 3

What must happen to food before it can be used by our body?

Answer 3

Food material must be broken down into nutrients that the cells of the body can absorb and use for energy.

Question 4

What is the function of our mouth and teeth when eating food?

Answer 4

Food enters the mouth, where it is broken down into smaller pieces by the teeth. Cells in the mouth release chemicals that help with this breakdown. Swallowing moves the food into the esophagus.

Question 5

What is the function of our esophagus when eating food?

Answer 5

Muscle cells lining the walls of the esophagus help push food down
into the stomach.

Question 6

What is the function of our stomach when eating food?

Answer 6

Cells in the stomach release chemicals that further break down the food. Stomach muscles contract and relax, moving food into the intestines.

Question 7

What is the function of our intestines when eating food?

Answer 7

In the intestine, the nutrients are absorbed into the blood vessels of the circulatory system and are transported to other parts of the body.

Question 8

What is the function of our anus when eating food?

Answer 8

Undigested food is passed out of the anus as waste.

Question 9

What is the function of our kidneys when eating food?

Answer 9

The cells of the body use these nutrients for energy and pass wastes into the blood for removal from the body. These wastes pass through the kidneys and are eliminated as urine. Each cell involved in this process has a unique task that is necessary for digestion.

Question 10

How do earthworms obtain nutrients?

Answer 10

The earthworm has a small mouth leading to a pharynx. Earthworms “suck” in food using the pharynx. The esophagus then pushes food into the crop, an organ that moistens and stores food. A specialized stomach called the gizzard contains particles of sand and gravel that help break down tough foods. In the intestine, chemicals further break down the food into nutrients that can be absorbed into the cells of the body. Undigested food is passed through the anus as waste.

Question 11

Define ‘xylem vessels’.

Answer 11

Xylem vessels are a system of tubes in a plant that transports water and minerals from the roots to the shoots and leaves.

Question 12

Define ‘phloem vessels’.

Answer 12

Phloem vessels are a system of tubes in a plant that transports nutrients (such as dissolved sugars) from the leaves to the rest of a plant.

Question 13

If plants can’t hunt for nutrients like animals do, how do they obtain them?

Answer 13

Plants cannot hunt for nutrients as animals do. Instead, they obtain nutrients directly from their environment. Plants use roots to absorb water and nutrients from the soil.

Question 14

What is used for photosynthesis?

Answer 14

The plant leaves use sunlight, carbon dioxide, and water to make food by photosynthesis.

Question 15

Where are excess sugars in a plant stored?

Answer 15

Excess sugars are transported to the stems and roots for storage.

Question 16

Which of these are bigger? Xylem vessels or phloem vessels?

Answer 16

Xylem vessels

Question 17

How do earthworms obtain oxygen?

Answer 17

Small multicellular organisms use diffusion to obtain oxygen. For
example, the earthworm uses its moist skin to exchange gases with
the outside air.

Question 18

How is the may aquatic animals obtain oxygen different from the way land animals get it?

Answer 18

Some aquatic organisms, like fish, pass oxygen-rich water through gills, where it diffuses into blood capillaries. Most land animals use lungs for gas exchange. In all cases, oxygen is absorbed from the environment, and carbon dioxide is removed from the blood.
The dissolved gases are transported in the blood.

Question 19

What is the function of the trachea when breathing air?

Answer 19

In humans, air is inhaled through the mouth and nose and passes into the trachea. A flap-like structure in the trachea opens when you breathe, but closes when you swallow food. This prevents food from entering the trachea and lungs.

Question 20

What happens in the lungs when breathing air?

Answer 20

Air travels down the trachea into the lungs. In the lungs, tubes called bronchi branch off into smaller tubes called bronchioles. At the end of the bronchioles are round sacs of alveoli, where gas exchange occurs. The walls of the alveoli are only one cell thick. This allows oxygen to diff use out of the cells of the alveoli and into the blood cells.

Question 21

What is the function of the circulatory system when breathing?

Answer 21

The circulatory system transports the oxygen-rich blood cells to the rest of the body. As blood circulates throughout the body, oxygen diffuses out of the blood cells and into the cells of the body. In the same way, carbon dioxide diffuses out of the body cells and
into the blood cells. Blood cells are carried to the alveoli. Carbon
dioxide diffuses out of the blood cells and into the alveoli. The carbon dioxide then travels through the bronchioles, bronchi, and trachea. It is removed from the body when you exhale.

Question 22

True or False - All vertebrates exchange gases in the same way.

Answer 22

False

Question 23

How does a frog breathe under water?

Answer 23

When a frog is underwater, its skin
becomes permeable to water and gases. Blood vessels in the cells of the moist outer skin allow oxygen to diffuse from the water into the bloodstream. In the same way, carbon dioxide diff uses out of the blood cells into the water.

Question 24

How does a frog breathe on land?

Answer 24

On land, a frog uses lungs similar to those of humans for gas exchange. Air is forced into the lungs by a gulping motion (which fills the throat and causes it to bulge). Oxygen then diffuses into the bloodstream from the lungs.

Question 25

How does gas exchange occur in plants?

Answer 25

Plants have special tissues containing stomates, which they use for gas exchange. Stomates are microscopic pores that control
the movement of gases and water
vapour into and out of the plant.
Stomates are mainly found on the
bottom surface of a leaf but can also be found in other parts of the plant, including the stems.

Question 26

True or False - All vertebrates and some invertebrates have a complex nervous system.

Answer 26

True

Question 27

How do our nervous system’s work?

Answer 27

Nerve cells are highly specialized to process and transmit information. Nervous systems respond to factors in the environment (such as temperature) by sending signals through the nerve cells, or neurons, to organs. These signals are sent to the brain where they are processed, and a response is initiated.

Question 28

Give an example on how the nervous system works.

Answer 28

For example, a cat may see a saucer of milk. Information from the cat’s eyes travels along nerve cells to the brain, where the brain processes the information. If the brain decides it wants the milk, the brain sends a signal to the muscles in the cat’s limbs, and the cat moves to the saucer of milk and drinks it.

Question 29

True or False - Each time an organism responds to a change in its environment, a short chain of messages travels through the nervous system.

Answer 29

False

Question 30

How do plants respond to the environment (one example)?

Answer 30

Plants are also able to respond to their environment. For example, specialized cells in the leaves of trees detect the decrease in sunlight as winter approaches. Chloroplasts then reduce production of green chlorophyll. As existing chlorophyll is broken down, other coloured particles are revealed, creating the red- and orange-coloured leaves we see in autumn. The leaves eventually die and fall off . In the spring, increased sunlight and warmer temperatures promote the production of new leaves containing large amounts of chlorophyll, and the green colour returns to the leaves.

Question 31

How do bones and muscles work together for movement to occur?

Answer 31

Muscles and bones work together to allow vertebrates to move around. The human musculoskeletal system is made up of more than two hundred bones that support the hundreds of muscles in the body. The muscles are attached to the bones in ways that move the bones when the muscles contract.

Question 32

How are muscle contractions controlled?

Answer 32

Muscle contractions are controlled by signals from the nervous system.

Question 33

What role do muscles play?

Answer 33

Muscles also play an important role in the functioning of organs. For example, muscle cells in the walls of the heart contract to move blood into and out of the heart. Muscle cells use a lot of energy. For this reason, they have many mitochondria that convert food energy into motion.

Question 34

Do invertebrates also use bones and muscles to move?

Answer 34

Invertebrate animals also use muscles to achieve locomotion, but most do not have bones. The earthworm, for example, uses muscle contractions for locomotion. The earthworm anchors itself to the soil with tiny hair-like projections, and then muscles in the body contract and expand to pull the body through the soil.

Question 35

True or False - Invertebrate animals also use muscles and bones to achieve locomotion.

Answer 35

False (Most of them don’t have bones)

Question 36

Give an example on how muscles help with movement.

Answer 36

When the tricep is contracted, the arm is extended. When the bicep is contracted, the arm is pulled up and the elbow bends.

Question 37

Which parts of the digestive system of the earthworm are also in the human digestive system?

Answer 37

As we know, in human digestion, our mouth, esophagus, stomach, intestines, and our anus play very important roles. We can see that earthworms also have an esophagus, intestines, and an anus.