2.4: How Scientists Classify Living Things
(Answer Key)
1. Which two groups of organisms have people always recognized?
People usually recognize the plant and animal groups of organisms.
2. How is it that scientists now have a better picture of how organisms are alike or
different?
After the development of magnifying tools such as microscopes scientists were able to look at
organisms that were not visible to the naked eye. They also looked at internal structures as
well as external structures. Both of these things give them a better picture of how organisms
are alike or different.
3. What is the difference between unicellular and multi-cellular organisms?
Unicellular organisms are made of only one cell while multi-cellular organisms are made of
more than one cell.
4. Why do multi-cellular organisms need all of its cells to work together?
Each type of cell has its own structure and purpose and all of the cells need to work together
to ensure that the organism can perform the functions it needs to survive.
6. Name the five kingdoms of living things:
The five kingdoms are Monera, Protista, Fungi, Plantae and Animalia.
8. Why is classifying organisms by kingdoms a good beginning but not really enough?
There are many, sometimes millions, of organisms within each kingdom. Scientists needed a
way to classify them into smaller, more manageable groups. They also needed a common way
of identifying and naming organisms so they can describe, compare and communicate their
knowledge about different organisms.
9. Who created the single scientific system for classifying organisms that is used by
scientists today?
Carolus Linnaeus created a single classification system for classifying organisms.
10. When did he create the new system?
He created the system in 1735.
11. How many categories did he create and what were they? (Be sure to list them in
order.)
He created seven categories which were: kingdom, phylum, class, order, family, genus, and
species.
12. What other system did Linnaeus develop?
He also created a two-part Latin naming system for naming organisms.
13. Why did he create this system?
He created this system to make it easier for scientists around the world to communicate about
the same organism.
5a) What do we mean by species?
5a) Organisms that belong to the same species are capable of breeding together and having
offspring that can also reproduce.
5b) What do we mean by unicellular?
5b) An organism made of only one cell.
5c) What do we mean by multi-cellular?
5c) More complex organisms made of more than one cell.
5d) What is a cell membrane?
5d) The membrane is the thin covering around the entire cell. It encloses the cell’s contents
and acts like a gatekeeper by allowing useful materials in and waste to move out.
5e) What is a cell wall?
5e) A cell wall is only found in plant cells. It helps protect the cell and provides support and
structure for the plant.
5f) What is a nucleus?
5f) The nucleus acts as the control centre or “brain” of the cell. It directs all of the cell’s
activities such as movement and growth.
5g) What is cytoplasm?
5g) Cytoplasm is the thick liquid that fills the cell. It is where the work of the cell is carried
out.
5h) What are vacuoles?
5h) Vacuoles are bubble like structures that store water and nutrients.
5i) What are chloroplasts?
5i) They are the cell structures that contain chlorophyll and are found only in plant cells.
5j) What is chlorophyll?
5j) It is the green pigment found in chloroplasts that give plants their green colour.
7a) What are the characteristics of Kingdom Animalia?
7a) – multi-cellular
- Feed off of living things
7b) What are the characteristics of Kingdom Plantae?
7b) – multi-cellular
- Make their own food through photosynthesis
7c) What are the characteristics of Kingdom Fungi?
7c) – mostly multi-cellular
- Feed off living things
7d) What are the characteristics of Kingdom Protista?
7d) – mostly uni-cellular, some multi-cellular
- More complex cell structure than Monera
7e) What are the characteristics of Kingdom Monera?
7e)- uni-cellular
- Most basic cell structure
- Does not have a true nucleaus