BIOLOGY 1 Marks Question

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

Cellular level of organisation.

Coelom in Ascaris is a pseudocoelom because it is not completely lined by mesoderm; mesoderm occurs as scattered pouches in between ectoderm and endoderm.

Ornithorhynchus.

Bioluminescence is the property of living organisms to emit light.

Herdmania, Salpa, Doliolum, Ascidia, Oikopleura, etc.

In bilateral symmetry, the body can be divided into identical left and right halves in only one plane.

Cephalochordata and Urochordata.

Animals possessing coelom are called coelomates, e.g. annelids, molluscs, arthropods, etc.

Closed type digestive system.

Flatworms have flame cells for osmoregulation and excretion.

Reptilia are crawling animals and their skin is hard and dry to withstand extreme temperatures.

Porifera.

Notochord is a flexible rod-like material similar to cartilage present on dorsal side between alimentary canal and nervous system in some animals. It is derived from mesoderm. Notochord is found in chordates (atleast in some stages of their life cycle, e.g., vertebrates).

Pseudometamerism is found in tapeworms.

Aschelminthes.

Metagenesis is the phenomenon of alternation of generations, in cnidarians, i.e., polyps produce medusae asexually and medusae produce polyps sexually. Ex.- Obelia.

In coelomates the mesoderm is lining the body cavity, while in acoelomates the mesoderm is present in small pouches.

Mouth; on hypostome.

Flame cells.

1. Choanocytes/ collar cells.
2. Intracellular digestion.

Radula is a small tooth like structure present in the members of phylum molluscs, which helps them to chew the food from the surface of plants and rocks.

1. Cnidaria, Ctenophora.
2. Echinodermata.

Every living form maintains a proper shape, size and structure. In multicellular lower organisms the shape of body is maintained by certain biological materials like chitin and calcium substances. Chitinous exoskeleton is the characteristic feature of arthropods. (e.g., cockroach, termite. wasp) whereas, calcareous shell is present in mollusks (gastropods). (e.g., snail and slugs).

Cnidaria is divided into following three classes:

1. Hydrozoa.
2. Scyphozoa.
3. Anthozoa.

They are called flatworms because they have a dorsoventrally flattened body.

An organ, which regulates buoyancy: Air bladder.

Internal shell-In Sepia (cuttle fish), Loligo (squid) Shell absent- Octopus (devil fish).

1. Planaria.
2. Hydra, Adamsia.

Antennae and statocysts.

In Limax (slug) and Helix (land snail).

Homeothermy is common feature of Aves and mammals.

3. Mollusca bogo.

Placoid scales are found in cartilaginous fish, e.g. scoliodon. Cycoid scales are found in bony fish, e.g. rohu.

Cnidocytes.

Columba (Pigeon).

Digestive system in reptiles is well-developed with acrodont teeth in both jaws. Reptiles have three-chambered heart with two auricles and one ventricle.

Arthropods have compund eyes. Aquatic forms of arthropods also have statocysts for balancing.

Crocodilus.

Corallium nobile (red coral).

Crop and gizzard.

It is made of spicules or spongin fibres.

In some cnidarians, polyps reproduce medusae asexually and medusae form the polyps sexually. Such alternation of asexual and sexual phases in the life cycle of cnidarians is called metagenesis e.g., Obelici.

Hydra and Adamsia.

1. Malpighian tubules.
2. Nephridia.

Coelenterata.

Ascariasis caused by roundworm or Ascaris.

Skeleton in annelids is absent. Coelomic fluid acts as hydrostatic skeleton which maintains its body shape.

In direct development the embryo directly develops into an adult, while in indirect development there is an intermediate larval stage. Certain members of Arthropods show larval stage of development.

Both have open circulatory system.