Paragraph 4.1-4.11

Summary Biology unit 4

4.1 Classifying organisms

You can classify organisms in four kingdoms; bacteria, fungi, plants and animals. To classify you study features of organisms, such as how they move, or where they live. You also study the way their cells are built. Such features are cell walls, nuclei and chloroplasts.

bacteria

fungi

Plants

Animals

Cell wall

Yes

Yes

Yes

No

Nucleus

No

Yes

Yes

Yes

Chloroplasts

No

No

Yes

No

Organisms that have a lot in common do not always belong to the same species. For example; an African elephant and an Indian elephant look quite similar, but they don’t belong to the same species. Dachshunds and Great Danes do not have a lot in common, but they belong to the same species.

A species in a group of individuals that can produce fertile offspring, which means that the offspring can also mate and have young.

4.5 Animal kingdom

SYMMETRY

There are many different ways of classifying animals into smaller groups. Scientists use two features: symmetry and skeleton.

Many organisms are bilaterally symmetric. These animals are divisible into two more or less identical parts in only one way.

Animals that are divisible in more than two ways are radially symmetric.

Animals that are not divisible are asymmetric.

SKELETON          

There are different kinds of skeleton. Some animals have a hard, tough skin. This skin is called an external skeleton.

Other animals have a skeleton inside their body, this is called an internal skeleton.

Some animals don’t seem to have any skeleton. In fact, their bodies are filled with liquid.

 Eight phyla of the animal kingdom

1. Unicellular animals

-made of one cell

- no skeleton

- asymmetric

- live in water

2. Sponges

- asymmetric

- live in water

- skeleton made of spicules

- are sessile

3. Cnidarians

- no skeleton

- live in water

- capture prey using their tentacles

4. Worms

- no skeleton

- bilaterally symmetric

- long, thin body

5. Molluscs

- shell as skeleton

- bilaterally symmetric

6. Arthopods

- cuticle as skeleton

- bilaterally symmetric

7. Echinoderms

- covered with spines

- internal skeleton made of calcium carbonate

- radially symmetric

- live at the bottom of the sea

8. Vertebrates

- internal skeleton

- bilaterally symmetric

4.6 Unicellular animals

Unicellular animals are made of one cell. This means that all the life processes take place inside the one cell. Amoebae and Paramecia are examples of such unicellular animals. Both live in water.

AMOEBA

An amoeba can change is shape. It pushes out pseudopods in the direction it wants to go. The cytoplasm follows and fills the pseudopods, pulling the rest of the cell with it.

Amoebae eat algae, bacteria, plant cells, and other smaller things. They eat by surrounding tiny particles of food with their pseudopods. The food is taken into the cytoplasm forming a food vacuole. Such a food vacuole is not the same thing as a vacuole in a plant cell. The food vacuole digests the food. The nutrients are taken up into the cytoplasm. Waste products are transported outside the cell through the cell membrane.

PARAMECIUM

Simple cilia cover the body and beat in a single direction. This beating allows the body to move. The cilia are also needed for feeding the paramecium. The cilia move food particles in the direction of the mouth pore. From the cell mouth these food articles enter a food vacuole in which the food in digested. The nutrients obtained are taken up into the cytoplasm and the waste products are secreted through the anal pore.

4.7 Arthropods

Arthropod means ‘jointed legs’. This means that their legs are divided into segments. Crustaceans, insects, arachnids and myriapods are four classes that belong to the phylum arthropods.

The bodies of arthropods are segmented as well. Myriapods have long bodies made up of lots of segments. Legs are attached to each segment.

INSECTS

The body of an insect is divided into three parts: the head, the thorax and the abdomen. The head has eyes and antennae. The thorax has legs and usually wings as well.

Insects have the most species within the arthropods.

4.8 Vertebrates

Vertebrates have an internal skeleton. The spinal column consists of vertebrae and is part of the skeleton.

CLASSIFICATION OF VERTEBRATES

Vertebrates can be classified into five different classes: fish, amphibians, birds, reptiles and mammals. These classes are separated because of the following characteristics:

1                     Skin. The skin of vertebrates can be covered with scales, with slime, feathers or hair.

2                     Body temperature. The warm blooded animals have a constant temperature. Cold blooded animals have a temperature that changes with the outside temperature. So their body temperature isn’t constant.

3                     Breathing organs. Vertebrates have lungs or gills for breathing. Some vertebrates are able to breathe through their skin.

4                     Reproduction. Many vertebrates lay eggs. Eggs can be protected by hard shells or leathery shells. Some eggs are not protected. They don’t have any shells. Some vertebrates don’t have young that hatch from eggs. These young are born alreadu well developed. These animals are said to give birth to live young (viviparous)

5                     Environment. Some vertebrates live on land. Others live in the water or are able to fly. Some of them can live both on land and in the water. Most mammals live on land, but some mammals live in water.