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.

Young ones of most of the amphibians which are aquatic show branchial respiration.

About 6000.

Osculum, the water enters through ostia and moves out through osculum.

They are described as acoelomates because body cavity or coelom is absent; it is filled with a parenchyma-like tissue.

1. Forelimbs are modified into wings.
2. Bones are pneumatic for weight reduction.

• Rana- Cold-blooded.
• Scoliodon- Cold-blooded.
• Penguin- Warm-blooded.
• Blue whale- Warm-blooded.

It is used by fishes to note the changes in surrounding water.

This is because it supplies deoxygenated blood to gills for oxygenation.

Sycon.

Porifers and coelenterates.

Mammals are unique due to following features

1. Presence of milk producing mammary glands in females.
2. Hairs present on the whole body.

A viviparous animal: Panthera leo (lion).

Ctenoid or cycloid scales.

When the coelom is completely lined by mesoderm, it is a true coelom.

Pneumatic bones are hollow and hence are light weight. They help to reduce the weight and hence help the birds in flight. They also provide support.

Annelids have closed circulatory system and excretory organs are nephridia. Nephridia are present in each segment.

Aschelminthes.

1. Cobra - Naja.
2. Krait - Bangarus.
3. Viper - Vipera.

Because they have single opening both for ingestion and egestion.

Segmentation is metameric when the animal body is externally and internally divided into segments with a serial repetition of at least some organs.

The similarities between the two are: Aves and mammals- They both are warm-blooded animals and have a four-chambered heart.

Following are the role of feathers in birds:

1. They create airfoil shape for wings. This provides lift during flight.
2. They help in maintaining body temperature.
3. Play important role in mating.

Two modifications in reptiles required for terrestrial mode of life are:

1. Respiration by lungs.
2. Internal fertilization.

It is found in Platy helminthes. Pseudosegmentation is the formation of new segments through budding or strobilation.

Struthio (ostrich-a flightless bird) and Ornithorhynchus (platypus-an egg laying mammal).

Chordates.

Ascaris.

1. Bilateral symmetry means that an animal can be cut into two equal left and right halves along only one plane, passing through the centre, e.g. human beings.
2. An animal is acoelomate, if the body cavity, called coelom, is absent, e.g. tapeworm.

In non-vertebrates vertebral column is absent, while it is present in vertebrates.

Platypus.

Frog and birds.

1. Struthio.
2. Ornithorhynchus.

Bilaterally symmetrical; the back side of our body is dorsal and the front side is ventral.

Parapodia.

Ectoderm and endoderm.

Trygon.

Limbless reptile– Naja naja, Limbless amphibian- lchthyophi.

Class-Cyclostomata is comprised of, the living jawless fishes. Their mouth is circular and lack jaws; hence they are also called agnathans. It works like a sucker and is surrounded by tentacles (e.g., lampreys and hellish). These also press retractable horny teeth.

The mesoglea in ctenophores also contains amoebocytes, elastic fibres and muscle cells.

Both are oviparous and fertilisation is external.

Blood-filled cavity in arthropods is haemocoel and lateral appendages in aquatic annelids are parapodia.

This is because caudal fin has equal lobes.

The notochord is mesodermally derived structure formed on the dorsal side during embryonic development in some animals.

The empty space in pneumatic bones helps in weight reduction of skeleton in birds. It is a kind of flight adaptation in birds.

Pleurobrachia and Ctenoplana are animals which exhibit bioluminescence. These animals belong to the phylum Ctenophora.

Members of Cnidaria and Ctenophora have tissue level of organisation.

Chondrichthyes.

Chordates have dorsal notochord at some stages of life, while notochord is absent in non-chordates.

Cnidoblasts are special structures containing stinging capsules. The poisonous substance from the stinging capsule is used to kill the prey.

Cnidarians have basically two types of zooids, i.e., polyp (cup-shaped) and medusa (umbrella-shaped). This phenomenon is called polymorphism (metagenesis).

Animal, which exhibits alternation of generation: Obelia (Sea-fur).

Since the air bladder is absent, they have to swim constantly to avoid sinking.

Malpighian tubules.

Parapodia are the lateral triangular appendages that help in swimming; it is found in Nereis.

Amphids are pits commonly having olfactory chemoreceptors. Phasmids are glandulo-secretory porous sensory structures.

In annelids, haemoglobin is present in plasma, while in vertebrates it is present in RBCs.

Oviparous animal with mammary gland: Echidna (Platypus).

Vertebral column.

Since the body surface of annelids is distinctly marked into ring-like (L.annulus - little ring) metameres, they are named so.

Ascaris and Enterobius (pinworm).

1. Spongilla.
2. Obelia.

Arthropods are the first animals evolved the endocrine system. Some insects release pheromones that act as sex attractants by which males can locate females even if it is present far away from them.

Hemichordata.

Chelone (Turtle).

Hydrostatic skeleton is a system of water-filled spaces that act as turgor operated chambers or valve for movements and pressure points.

Adamsia.

In tapeworms body is divided into number of segments called proglottids that are budded off from the neck. Each segment is able to perform all the vital functions of body. This type of segmentation is called pseudometamerism or pseudosegmentation.

Notochord is a mesodermally derived rod-like structure formed on the dorsal side (found only during embryonic stages or throughout life) in some animals.

This is because the soft body of urochordates is surrounded by a thick test or tunic, often transparent or translucent.

Ctenophora; Comb-jellies.

Cnidaria and Echinodermata.

The similarities between the two are: Frog and crocodile- Both can live on land as well as water. Both use lungs for breathing.

The similarities between the two are: Turtle and Pila- Both have a hard covering protecting their body. Both are oviparous.

In Urochordata, the notochord is restricted to the tail region, only in the larval stage; in Cephalochordata, it extends from head to tail and persists throughout life.

Annelida.

Coelenterata is called Cnidaria because of the presence of stinging cells called cnidoblasts or nematoblasts.

	Complete Digestive System	Incomplete Digestive System
1.	When the digestive system has two openings, the mouth for ingestion and the anus for egestion, the digestive system is said to be complete. e.g. human beings.	When the digestive system has only one opening for both ingestion and egestion, the digestive system is said to be incomplete. e.g. Hydra.

Birds have food storing crop and food masticating gizzard, which helps them to grind the food.

Few common features of all vertebrates are

1. Organ system organisation
2. Bilateral symmetry.
3. Triploblastic germ layers.

They have jointed legs/ appendages (arthros-joint; poda-appendages).

Planaria.

They are called roundworms because their body is circular in outline in a cross-section.

A fish possessing an electric organ: Torpedo.

1. Limbless reptile-Snake

Limbless amphibian-Ichthyophis

1. Oviparous mammal-Duck-billed platypus

Planaria.

1. Mesogloea.
2. Medusa.