Zoology

Question 1

True Tissues

Answer 1

In a true tissue, cells of the same kind are grouped together to perform one or more specialized function e.g. nerve tissue, muscle tissue. True tissues work in harmony, they are coordinated.

Question 2

Symmetry

Answer 2

Symmetry in animals is the quality of being made up of exactly similar body parts in a particular arrangement.

Question 3

Radial symmetry

Answer 3

symmetry about a central axis e.g. Sea anemone. These organisms have a top and a bottom

Question 4

Bilateral symmetry

Answer 4

being divisible into symmetrical halves on either side of a single unique plane

Question 5

Animals that are bilaterally symmetrical

Answer 5

dorsal (top), ventral (bottom), anterior (head), posterior (tail)

Question 6

Cephalisation

Answer 6

Bilateral symmetry allows for the development of a specialised head with a concentration of nerve cells and sense organs. Having a brain and associated sense organs is an advantage for nervous coordination and forward movement in animals

Question 7

Embryonic tissue layers

Answer 7

The developing embryo of all animals with specialised tissues starts a mass of cells. This mass folds inwards and expands to form two distinct layers of cells. The outer layer is called the ectoderm layer and the inner layer is called the endoderm layer. The ectoderm goes on to develop into various specialised tissues and organs (e.g. skin) and the endoderm likewise continues to develop into specific tissues and organs e.g. the gut lining. In many animals, a third distinct embryonic layer forms between the ectoderm and endoderm called the mesoderm. This layer of embryonic cells goes on to develop into various specialised tissues and organs that are found between the gut and the skin.

Question 8

Coelom

Answer 8

The coelom is a body cavity between the mesoderm layer/s of some animal bodies. Some triploblastic animals have a solid body with no body cavity within the mesoderm, these are called acoelomate (no coelom). Animals with a cavity within the mesoderm are called coelomate. When there is a cavity but it is not completely lined by a mesoderm layer then it is called pseudocoelomate

Question 9

Advantages of a coelom include:

Answer 9

Allows more complex organs to develop such as digestive organs, muscular system, blood system etc.

Allows the creation of a hydrostatic force to be generated for movement in soft-bodied animals.

It separates the endoderm and ectoderm from each other with a cavity which allows the layers to move independently of each other. This allows peristalsis to occur.

In some organisms, the coelomic fluid (fluid found in the coelom) helps to transport nutrients and waste in the body.

Question 10

Through-gut

Answer 10

Animals with only one opening to the gut will consume food through the opening (mouth) and defecate undigested waste through the same opening. Animals with two openings to the gut can consume food through a mouth opening and defecate waste through another opening called the anus. This type of gut is also called a through-gut. A through-gut is an advantage because food can be consumed continuously because it moves through the digestive system. Sections of the digestive system can also specialize (e.g. stomach) to improve the efficiency of the digestive process. The Annelida, Arthropoda and Chordata all have a through-gut.

Question 11

Exoskeleton

Answer 11

A solid skeleton positioned on the outside of the body

Question 12

Endoskeleton

Answer 12

A solid skeleton positioned on the inside of the body. It consists of bones and/or cartilage.