7.5
All organisms can be divided into five kingdoms In this topic, you will learn that:
unicellular consisting of only one cell; an example is bacteria taxonomist a scientist who classifies living things into groups
Building blocks of life
Kingdom Animalia
Cells are often called the building blocks of life. Think of the way bricks are used to build a house. Cells build living things in a similar way. However, there are usually many more cells in living things than bricks in a house. Any living thing with more than one cell is multicellular. Many living things, such as bacteria, consist of only one cell. These are single-celled or unicellular organisms.
All organisms in this kingdom are multicellular. Each cell stores its genetic material in a nucleus but does not have a cell wall. Animals gain energy from other living things. We belong in this kingdom. Zoologists are the scientists who study animals.
Parts of a cell
cell wall a structure that provides support around the cell in some organisms, such as plants and fungi
a
b
a
Taxonomists ask three questions when they are trying to classify the cells of an organism:
1 Does the cell keep all of its genetic material (called DNA) inside a nucleus? The nucleus protects the DNA that carries all the instructions for living and reproducing.
c
2 Does the cell have a cell wall around it for extra support?
D
nucleus a membrane-bound structure in cells that contains most of the cell's genetic material
• the nature of science is to change and develop as new evidence becomes available.
AF T
multicellular consisting of two or more cells
• new information that compares genetic material may change the five kingdoms
R
Interactive 7.5 Kingdoms
• taxonomists are scientists that classify living things
3 Does the cell use sunlight to make its own nutrients (autotroph)? Plant cells can do this, but fungi (like mushrooms) need to absorb their nutrients from other living things (heterotrophs). These three features are used to divide all living things into the fi rst big group called kingdoms.
b
c
Figure 2 Kingdom Animalia: a the proboscis monkey (Nasalis larvatus); b the Port Jackson shark (Heterodontus portusjacksoni ); and c the damselfly (Calopteryx virgo)
Kingdom Plantae Plants include trees, vines, bushes, ferns, mosses, weeds and grasses. They all gain energy by converting the energy from sunlight into food (autotrophs). They are multicellular and their cells have a cell wall around the outside of the cell, as well as a nucleus inside the cell. Botanists are the scientists who study the plant kingdom.
Figure 1 a Simple animal; b, plant; and bacterial cells
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