Structural Organization in Animals
All important functions like digestion, respiration and reproduction in unicellular organisms are performed by a single cell but in the complex body of multicellular animals, the same basic functions are carried out in a well organized manner by different groups of cells . The body of a simple organism like Hydra is made of thousands of different types of cells. In multicellular animals, a group of similar cells along with intercellular substances perform a specific function and such an organization is called tissue. All complex animals consist of only four basic types of tissues and they are organized in specific proportion and pattern to form an organ like stomach, lung, heart and kidney.
Very Short Answer Questions [1 Marks Question]
What is invert sugar? [1 Mark]
Answer: Invert sugar is a mixture of glucose (dextrose) and fructose which is produced from sugar (sucrose) by application of heat and an acid such as cream of tartar or citric acid affecting the sweetness, solubility, and amount of crystallization in candy making.
What are the conditions due to which glucose is converted into gluconic and saccharic acid? [1 Mark]
Answer: Glucose is converted to gluconic acid when we oxidate with bromine water and when the oxidation is carried by conc. HNO3 is then converted into saccharic acid.
What are the cellular components of blood? [1 Mark]
Answer: Peripheral blood is composed of an isotonic fluid, called plasma, in which various blood cells are suspended. The major categories of the peripheral blood cells are:
1.Erythrocytes (red blood cells) 2. Leukocytes (white blood cells) 3.Thrombocytes (platelets)
What the functions of nephridia in the body of an earthworm. [1 Mark]
Answer: Nephridia helps in removal of the waste products from the body of the earthworm. It is an invertebrate organ which is found in pairs and performs a function which is similar to the vertebrate kidneys.
What is the function of Uterus in frog? [1 Mark]
Answer: In frogs, two uterus are connected to the kidney. In male frogs, the uterus opens into cloaca and helps in passing the urine and sperm. In female frogs, it opens separately into cloaca and helps in excreting urine.
Short Answer Questions [2 Marks Question]
How many monosaccharide units are there in the sugar which is present in the milk? [2 Marks]
Answer: The sugar which is present in milk is Lactose which is a disaccharide sugar consisting of two monosaccharide units- D-glucose and D-galactose.
In a polysaccharide, what linkage connects all the monosaccharide units? [2 Marks]
Answer: The linkage which connects all the monosaccharide units is β-1, 4’-glycosidic linkage (glycoside). It is basically a covalent bond which is formed between two or more monosaccharides in order to form a polysaccharide. The hemiacetal hydroxyl groups of two monosaccharides are replaced by two hydroxyl groups which belong to a third sugar residue and a branching point is produced in the molecule which then becomes a branched polysaccharide. The hemiacetal and hemiketal forms monosaccharides which then react with alcohols to form acetals and ketals which are called glycosides.
What are the types of nephridia? [2 Marks]
Answer: There are three types of nephridia which are based on location in the earthworm body are Septal, Integumentary and Pharyngeal. The septal nephridia are present behind the fifteenth segment on both sides of the intersegmental septa and they open into the intestine. Integumentary nephridia which opens on the body surface and lies attached to the body wall are present from the third segment to the last segment and the pharyngeal nephridia are present in fourth, fifth and sixth segments in the form of paired tufts.
What is the function of malpighian tubules? [2 Marks]
Answer: Malpighian tubule lies in the abdominal body cavity and empty into the junction between midgut and hindgut. The tubule cells actively transport urine constituents like potassium ions, water, urate ions, sugar, amino acids into the tubule. Each tubule is lined by glandular cells and they carry out excretion. The glandular cells in turn absorb all the excretory materials which are then converted into uric acid and released through the hindgut.
Describe the Body wall in the earthworm [2 Marks]
Answer: The body wall of the earthworm makes up the internal parts providing protection. The Mucus protects the body wall from bacteria and other pathogens which lie on the body wall and also assists in respiration by keeping the skin moist. The body wall consists of cuticle, epidermis, two muscular layers and the parietal layer of the coelomic epithelium thereby also serving as a receptor organ.
How does the respiratory system in earthworms work? [2 Marks]
Answer: Earthworms breathe through their skin as they do not have lungs. The oxygen and carbon dioxide pass through the earthworm’s skin via diffusion and for diffusion to occur, the earthworm’s skin must be moist and to do this body fluid and mucous and therefore, the Earthworms need to be in damp or moist soil. This is usually the reason why they surface at night when it is possibly cooler with the low evaporating potential of the air.
How do earthworms detect light even though they cannot see? [2 Marks]
Answer: Earthworms have the ability to detect light even though they cannot see because of the fact that they have tissue located at the earthworm’s head which is sensitive to light and they enable the earthworm to detect light and not surface during the daytime where they could be affected by the sun.
How do frogs benefit the environment? [2 Marks]
Answer: The frogs eat a lot of the insects, arachnids and other small animals that we consider pests which can even carry diseases. They are also good bio indicators because the frogs have permeable skin which can detect whether an environment is good or bad. If an area is populated with lots of frogs it indicates that the environment is good and safe and if an area has too few frogs or if the population of the frogs in the area seem to be declining it indicates that particular environment is probably bad and/or toxic.
What is the function of hepatic caecum in a cockroach? [2 Marks]
Answer: Hepatic caecum or hepatic cecum is a name for some crustaceans, insects and cephalochordates which is used in describing various physiological structures. The hepatic caecum performs some functions which are analogous to the functions of the liver in vertebrates. In cockroaches, the hepatic caeca which is a ring of 6-8 blind tubules is present at the junction of the foregut and midgut and their main function is to secrete digestive juices to facilitate digestion.
Long Answer Questions [3 Marks Question]
How does the digestive system in earthworms work? [3 Marks]
Answer: The digestive system is partitioned into many regions which consist of the pharynx, the esophagus, the crop, the intestine and the gizzard, each with a certain function. Food such as soil enters the earthworm’s mouth where it is swallowed by the pharynx and then it passes through the esophagus, which consists of calciferous glands which release calcium carbonate to get rid of the earthworm’s body with excess calcium. After the food passes through the esophagus, it moves into the crop where it is stored and then eventually it moves into the gizzard that uses stones which the earthworm eats to grind the food completely. The food moves into the intestines as gland cells and releases fluids which helps in the digestive process. The intestinal wall contains blood vessels where the digested food is absorbed and then it is transported to the rest of the body.
Describe the circulatory system in earthworms. [3 Marks]
Answer: The earthworm has a closed circulatory system. The circulatory system circulates blood exclusively through vessels. There are three main vessels: aortic arches, dorsal blood and ventral blood vessels which supply the blood to organs within the earthworm. The aortic arches function just like a human heart, and are responsible for pumping blood into the dorsal and ventral blood vessels. The dorsal blood vessels have the responsibility of carrying blood to the front of the earthworm’s body and ventral blood vessels are responsible for carrying blood to the back of the earthworm’s body.
Long Answer Questions [5 Marks Question]
Describe about reproduction in earthworms [5 Marks]
Answer: Earthworms are hermaphrodites which means that each earthworm contains both male and female sex organs which can produce sperm and egg respectively in each earthworm. Although earthworms are hermaphrodites, they mostly need a mate to reproduce and during mating, in order for the sperm to be exchanged, two worms lineup inverted from each other.
The earthworms have a pair of ovaries that produce eggs and each have two male openings and two sperm receptacles, which take in the sperm from another mate. The clitellum will form a slime tube around it thus filling it with an albuminous fluid. The earthworm will move forward out of the slime tube and As it passes through the slime tube, the tube will pass over the female pore picking up eggs. The tube continues to move down the earthworm and pass over the male pore called the spermatheca which contains the stored sperm which are called the spermatozoa.
The eggs then will fertilize and the slime tube will close off as the worm moves completely out of the tube. The slime tube forms an “egg cocoon” and is put into the soil. And at last, the fertilized eggs will develop and become young worms.
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