Animal Kingdom - Class 11 Medical Biology - Extra Questions

Elephant, cow, monkey, and whale.

• The fusion of male and female gamete in an external environment (water bodies) is called external fertilization. 
• The gametes (sperms and egg) are released into the environment in a large amount into the water bodies.
• In fishes, the eggs from female fishes are released into the water and male fish releases its sperms.
• The sperms swim in water and come in contact with the eggs and fertilizes the egg.

Crocodile belongs to Phylum Reptilia.

The image represents the external structure of the fish and the parts are labelled. 

Animals belonging to class Aves and Mammalia have a four chambered heart.

All mammals have certain characteristics which are common for every mammal. Mammals all are warm-blooded animals, they breathe air, have hair and moms gives birth to babies and feed their babies milk from mammary glands. 

The circulatory system in birds and mammals consists of oygenated and deoxydenated blood. However, they have a double circulation system where the oxygenated as well as deoxygenated blood remain separate. This is essential to maintain the body temperature efficiently over a wide range. As mammals and birds require to keep their body warm, they require a higher supply of oxygen. Thus, it is beneficial if the oxygenated blood remains separate as its mixing with deoxygenated blood can make the entire blood impure.

Animals of class Pisces have two-chambered hearts. The heart has an atrium and a ventricle. Fishes have simple circulatory systems. The blood circulates only once through the heart in the fish during one cycle of passage through the body. The blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body.

The adaptations in Reptiles to lead a complete terrestrial life are:-
1)  They have developed a thick, scaly skin that helps them to conserve moisture inside their bodies which helps them survive on land (especially in hot and dry areas).

Non Chordates	Chordates
1. The vertebral column is absent.	1. The vertebral column is present.
2. The central nervous system is solid and ventral.	2. It is hollow and dorsal.
3. If the heart is present, it is dorsal.	3. The heart is ventral.
4. If hemoglobin is present, it is dissolved in plasma.	4. Hemoglobin is present in Red blood cells.
5. No post-anal tail.	5. The anal tail is present.
6. E.g. Protozoa, Arthropods, Annelida.	6. E.g. Aves, Reptiles, Mammals.

Platypus belongs to the class Mammalia. Mammals give birth to young ones without laying eggs. Platypus is an exception to this characteristic. It is an egg-laying mammal. 

Fishes have a streamlined body. Flexing its bodies and using of the tail back and forth, It expands its muscles one side of its body while relaxing the muscles on the other side,  this motion moves them forward through the water.  It also uses its caudal fin ( back fin) to help in pushing them through the water. 

Crocodiles are not advanced lizards but can be called as advanced birds. Birds have descended from dinosaurs and are more closely related to crocodiles, than the crocodiles are related to lizards.

The body of hemichordates is worm-shaped and divided into an anterior proboscis, an intermediate collar, and a posterior trunk. The proboscis is a muscular and ciliated organ used in locomotion and in the collection and transport of food particles. 

• Mammals are animals that belong to the phylum Chordata.
• Mammals are characterized by the presence of mammary glands which are used to feed their young ones.
• They also have hair on their bodies and sweat and oil glands inside their skin.
• They also possess a four-chambered heart and have very well-developed digestive, reproductive, urinary, and reproductive systems. 
• The characteristics that mammals possess are the most advanced or the most developed amongst all classes of chordates. 
• Hence, mammals are considered to be the most advanced animals in the entire animal kingdom.
  

$$\textbf{Solution}$$

Fish like reptiles that evolved from land reptiles about 200 million years ago- $$\textbf{Ichthyosaurs}$$.

$$\bullet$$ Extinct organisms that evolved around 200 million years ago in the Mesozoic Era and shared similarities with a dolphin and a fish.

$$\bullet$$ Ichthyosaurs were actually reptiles that lived on land but which later adapted habitat into marine sea.

$$\bullet$$ They had the ability to travel in water at very high speed.

Balanoglossus is considered a connecting link between chordates and non chordates because it shows characteristics which are present in both the phyla. For example, Balanoglossus shows the presence of notochord and pharyngeal gill slits which is a characteristic feature of chordates. It also shows the presence of heart which is dorsal just like non chordates.

Reptiles are cold blooded organisms or poikilotherms which means they are not able to regulate their body temperatures. Their body temperatures change with the change in  temperature of the environment. For example, if the outer temperature rises their body temperature also rises and vice - versa. This can be explained from the observation that when the temperatures drops, these reptiles bask themselves in the sun whereas when the temperatures are high, they would hide under the shades. 

I think there may be some link between the size of animal's ears and their hearing. The animals with larger ears can hear well because their ears can collect more sound waves. 

Snake belongs to the class-Reptilia of phylum-vertebrates. Whereas, cow, monkey and whales belongs to class-mammalia and are fully developed animals. 

Bat, rat and cat belong to Class Mammalia and have the following common features
(a) All have notochord at some stage of their life.
(b) All are warm blooded.
(c) All have four chambered heart.
(d) Presence of exoskeleton in the form of hair. 

• In kingdom Animalia, non-chordates and chordates are classified according to the presence or absence of a notochord. 
• Vertebrata belongs to chordates due to their presence of a notochord, which in the adult stage is replaced by a bony or cartilaginous vertebral column.

So, the answer is 'Presence of notochord'.

The two egg laying mammals are 

Fasciola hepatica and Taenia solium are flatworms belonging to Phylum Platyhelminthes. They are commonly known as Liver fluke and Tapeworm respectively.

Characteristics of class - Mammalia are ; Developed mammary glands are found in females, mothers feed milk to young ones secreted by mammary glands. Their body is divided into head, neck, thorax, abdomen and tail. Hair are present as exoskeleton on the body. Ear pinnae (External ear) is present. They are warm-blooded. They respire through the lungs. The heart is four-chambered. The heart has 2 auricles and 2 ventricles. Most of the mammals are viviparous.
Examples are: Pteropus (bat), Homo (man), Herpestes (mongoose), Ratus (rat), Panthera (lion, tiger). 

Labelled diagram of Jelly fish

(a) The blue whale is the largest existing mammal.
(b) The elephant is the largest land mammal.

Vertebrates	Invertebrates
They have a backbone made up of vertebrae.	They do not have a backbone.
They can be cold-blooded or warm-blooded.	They are always cold-blooded.
They have a well-developed brain.	They do not have a well-developed brain.
Example: frog and lizard	Example: Earthworm and snail

The neck of a giraffe is made up of 7 large bones called cervical vertebrae. 

The Chordates are characterized by the presence of pharyngeal slits, muscular post-anal tail, notochord and dorsal hollow nerve cord. The organism in the given diagram, however, does not show any of these features but has a number of bands of cilia and mouth similar to the Tornaria larva of hemichordates. These features which are similar to embryological features of echinoderms and show chordate’s characteristics in the adult stage are characteristic of the  group Hemichordata which is known for being a link between the invertebrates and the chordates. 

1. Reptilia, 2. lizards, 3. snakes, 4. tortoises, 5. first, 6. adapted, 7. life, 8. dry land, 9. cold-blooded, 10: terrestrial, 11. warmer, 12. aquatic, 13. water, I4 -,return, 15. land, 16. breeding, 17. varies, 18. covered,19. horny, 20. scales, 21. two pairs, 22. limbs, 23. horny claws, 24. absent, 25. snakes, 26. lizards.

Reptilia

Reptile itself is a class (Reptilia) under phylum Chordata. Reptiles ruled the land, water, and air in the mesozoic era, but most of them became extinct about 65 million years ago. There are only four living orders: Rhyncocephalia, Squamata, Chelonia, and Crocodilia. Rhyncocephalia includes a distant relative of lizards, named tuatara. It is a living fossil and found only in New Zealand. Squamata is the order of lizards and snakes. Chelonia includes turtles and tortoises, both living primarily in water and on land. Their body remains covered by the hard carapace. Crocodilia is an order of large, lizard-shaped, and predatory reptiles. It includes crocodiles, gharials, alligators, and caiman. 

Bats have external ears, body covered externally with hair and mammary glands, and these don't have beaks and feathers like birds. Bats give birth to young ones and do not lay eggs like birds. Thus, Meena can differentiate these features and explain to her sister that, the bat is not a bird, but a mammalian.