Biodiversity of animals and their mode for living

Question 1

what animals are in Phylum Porifera

Answer 1

consist of animals such as sea sponges
sea sponges are the most primitive group of organisms from the six different animal phyla

Question 2

how do sponges live

Answer 2

Sponges are attached to solid surfaces such as rocks anddo notmove to find their food. Therefore, sponges can be described as completesedentaryorganisms. Sponges arefilter feedersthat feed by sweeping water into their body cavity. The body cavity is called thespongocoel. The hollow spongocoel is dotted with tiny openings. Each opening is a specialisedpore cellthatcontrols theflow of waterinto the sponge.

• Sea sponges do not contain any body tissues because thecellsall work independently, and can change from one type to another.
• The spongocoel is not a gut because itdoesnot producedigestive enzymes.Digestion takes place inside thefeeding cells.
• The space in the centre is not a coelom because there is no mesoderm.
• The body wall has no muscles.

Question 3

how do sponges live

Answer 3

Sponges are attached to solid surfaces such as rocks anddo notmove to find their food. Therefore, sponges can be described as completesedentaryorganisms. Sponges arefilter feedersthat feed by sweeping water into their body cavity. The body cavity is called thespongocoel. The hollow spongocoel is dotted with tiny openings. Each opening is a specialisedpore cellthatcontrols theflow of waterinto the sponge.

• Sea sponges do not contain any body tissues because thecellsall work independently, and can change from one type to another.
• The spongocoel is not a gut because itdoesnot producedigestive enzymes.Digestion takes place inside thefeeding cells.
• The space in the centre is not a coelom because there is no mesoderm.
• The body wall has no muscles.

Question 4

what animals are found in Phylum Cnidaria

Answer 4

sea anemones, jellyfish, bluebottles, hydra and coral.

Question 5

what are the basic features of Cnidaria

Answer 5

• Cnidaria isradially symmetrical.
• Cnidaria hastwo embryonic layersand, therefore, arediploblasticorganisms.
• Being diploblastic (without a mesoderm) means that they areacoelomate.
• Cnidaria has ablind gut(a single opening that serves as a mouth and anus).

Question 6

what a Cnidaria’s also known for

Answer 6

The scientific wordCnidariameans ‘nettle-like’ or ‘sting.’Therefore, Cnidarians are known for their painful (and sometimes deadly) sting. The painful sting results from their ectoderm thatcontainssense cells,muscle cellsandcnidocytes(stinging cells).Cnidocytes are specialised cells that canharpoonandpoison prey. The muscle cells in both the ectoderm and endoderm can stretch and contract to move any prey harpooned by the cnidocytes towards the mouth to be swallowed for internal digestion.

Question 7

do Cnidaria’s have a circulatory system

Answer 7

No. Cnidarians have no organs such as a heart or brain. They, therefore,donot requireany form of a circulatory system becausediffusionallows for the adequate exchange of water, nutrients and waste between itself and its environment.

Question 7

what are the two different body forms in the Cnidaria.

Answer 7

• Thepolypform is astationaryanimal with amouthand tentacles on the organism’ssuperior(top) side. Hydra, sea anemones and coral are the polyp form.
• Themedusaform looks like the polyp form turned upside down and flattened. The medusa form is free-swimming and is shaped like an umbrella with themouthon theinferior(lower) side of the organism

Question 8

what are Phylum Platyhelminthes

Answer 8

The biological name ‘Platyhelminthes’ literally means ‘flat worm’.This is an unfamiliar group of organisms to most of us because they are primarily internal parasites. Examples of Platyhelminthes are tapeworms, planarians and flukes.

Question 9

what are the basic features of Platyhelminthes

Answer 9

• They arebilaterally symmetrical.
• Due to its symmetry, shows basiccephalisationwith a ‘head’ on one end of its body.
• Platyhelminthes have three embryonic layers and are, therefore,triploblastic.
• Platyhelminthes areacoelomateand still only pose ablind gut(a single opening that serves as a mouth and anus).
• Platyhelminthes are typicallyhermaphrodites(it contains both male and female reproductive organs).

Question 9

what do Platyhelminthes do

Answer 9

Taenia solium is anendoparasite. This tapeworm has two hosts in its life cycle. The primary host is a human and the intermediate host is the pig.

T. soliumis along(up to 5 m in length),flattened,ribbon-like worm. The tapeworm is covered by a rigid externalcuticlethatprotectsit from the digestive enzymes of its host. The worm consists of ascolex(head), aneck,andstrobila(body segments). The strobila consists of several units calledproglottids. Each unit, however, is called aproglottis.

The head has two rows of curved chitinoushookson therostellumforattachmentto the intestinal wall of a human. It also has foursuckersto further aid attachment. The neck has a narrow region consisting of small proglottids. The neck region is responsible for forming new proglottids.

Flatworms do not have a respiratory system. Instead, they have pores on the surface of their flattened bodies that allow for the diffusion of gases such as oxygen and carbon dioxide. There are no blood vessels in the flatworms.

The diagram below illustrates the structure ofT. solium

Question 10

what are Phylum Annelida

Answer 10

The word”Annelida”translates into the English word,”segmentation.”Examples of annelids are earthworms, polychaetes and leeches.

Question 11

what are the basic features of Annelida

Answer 11

• Bilaterallysymmetrical.
• Triploblastic.
• Coelomateorganisms.
• Through gut(a separate mouth and anus).

Question 12

what do Annelida do

Answer 12

The earthworm is an excellent example of an annelid for us to use during this lesson. Most of us are very familiar with this little organism.

The body of the earthworm evolved into many tiny separate units calledsegments. Each segment has more or less thesame internal structure. The segments make the body moreflexibleand enable one part to workindependentlyof the other parts so that the animal can move more freely.

The advantage of segmentation and flexibility was that each segment could provide the organism with aunique function.This means that the organism could allow each organ-system to become more specialised and to divide the labour of different body systems into specific body segments. Division of work means that each segment could perform a specific functionindependentlyfrom the next. For example, the reproductive system can become more specialised and complex as it can function independently from other systems such as the digestive system or the respiratory system.

The diagram below is a longitudinal section through the front thirteen segments of an earthworm to show the closed blood system and gut. You will notice that each segment has the same blood vessels and gut apart from the five pairs of hearts.

Question 12

what is Phylum Arthropoda

Answer 12

The biological word”Arthropoda”means”jointed”(arthro)”foot”(poda). Examples of Arthropoda are insects, arachnids, crustaceans and myriapods.

Question 13

what are the basic features of Arthropoda

Answer 13

• Bilaterallysymmetrical.
• Triploblasticorganisms.
• Coelomate.
• Through gut(a separate mouth and anus).

Question 14

what do they do

Answer 14

A unique characteristic of Arthropods is their thick, waterproof, hardenedexoskeletonmade ofchitin. The exoskeleton can be of various shapes, so there is an enormous variation between different species. The hardened exoskeleton is rigid, so the arthropodsmust have legs with jointsso that they canmove.

The internal organs of arthropods are not in the coelom but are in a different cavity called thehaemocoel. The haemocoel contains thebloodpumped around the body by the heart of itsopen circulatory system. The bloodsoaksthe outside of the organs instead of being carried by blood vessels.The animal’s movement allows the primitive heart to beat. If the animal remains stationary, the heart will not beat.

Due to this insufficient method of blood circulation, and the heavy armour of the exoskeleton, the organisms are limited in size and are, therefore, mostly small. The diagram below illustrates the basic components of this phyla.

Question 15

what are Phylum Chordata

Answer 15

The biological word”Chordata”means”string.”The ‘string’ refers to thenerve cordorspinal cord. Therefore, all organisms belonging to this phylum will comprise a nerve cord towards thedorsal sideof the organism.

Question 16

what are the basic features of Chordata

Answer 16

• Bilaterallysymmetrical.
• Triploblastic.
• Coelomateorganisms.
• Through gut(a separate mouth and anus).

Question 17

what do Phylum Chordata do

Answer 17

Most chordate animals have anendoskeletonwith a vertebral column made up of many separate bones calledvertebrae. These animals are calledvertebrates. There are two groups of chordates that are very primitive and do not have vertebrae. These two groups and all the other phyla we have discussed are calledinvertebrates.

Chordate animals have aclosed circulatory system, in which blood is transported around the body inside ofveinsandarteriesof various sizes. The blood is circulated by thepumpingaction of theheart,while the respiratory gases in the blood diffuse across the thin walls of the smallest vessels (capillaries) in the tissues.