They were first of all observed by Christian de Duve in 1955. The lysosomes are tiny vesicles which are bounded by single membrane and are made from proteins and lipids. They are found in different organisms like in most of the animal cells and only in a few plant cells like yeast, fungi and in … Read more
It is also known as theory of natural selection. Charles Robert Darwin was (1809- 1882) an English naturalist published his famous book “ The origin of species by natural selection” in 1859. This theory is based on a mass of accurate observations and prolonged experiments. This theory led the whole scientific world to believe in … Read more
S.N Acraniata Craniata 1. They are exclusively marine. They are aquatic or terrestrial. 2. They are small sized chordates. They are mostly large sized vertebrates. 3. Appendages, cephalization and exoskeleton are absent. Appendages are two pairs usually, well developed head and exoskeleton present. 4. Coelom is enterocoelic, budding off from embryonic archenteron. Coelom is … Read more
Introduction Symmetry means the arrangement of body parts into geometrical designs. Many adult sponges that are irregular in shape are said to be asymmetrical. However, the sponges start their life from a radially symmetrical larva. Four types of symmetry are found in animals. They are: spherical symmetry, radial symmetry, bi-radial symmetry and bilateral symmetry. Spherical … Read more
Introduction of Amphibians Amphibians are the first group among the chordates that live outside water. Several new features for terrestrial life also developed in amphibians. Organs of locomotion and protection against desiccation are characteristics. They are not the true land vertebrates though they were the first to emerge from water. Most of the amphibians are … Read more
Introduction Mosquitoes are two-winged flying insects that suck blood from humans and other animals. They are found all over the world but are mostly common in humid and temperate climate. They are generally found in the dark places such as bushes, holes in the trunk of the trees, corners of the room, bookcase, near ponds … Read more
Introduction The silkworm is the larva or caterpillar or imago of the silk-moth that produces silk thread. The thread is used for making silk clothes and various other purposes. Raw silk is obtained from the cocoons of the silk-moth. The adult of silkworm is called silk-moth. Silk-moths are found in many indigenous varieties across the … Read more
Introduction Any change in an organism that makes it slowly or rapidly better suited to the environment is called adaptation. It can also be defined as the process of adjustment of an organism to its environment. It increases the possibility of survival of an organism for a longer time as it helps the organism to … Read more
The word Protozoa is derived from two Greek words: protos means first; zoon means animal. They are the first animals with a protoplasmic grade of body organization. They are simple, unicellular microscopic organisms which may be solitary or colonial. All the vital activities are performed by a single cell so no physiological divison of labour … Read more
Tetra-four, podos-feet Primarily terrestrial, some are secondarily aquatic. Two pairs of pentadactyl limbs. Body covered by an exoskeleton of epidermal hair, feathers or scales. Lungs are main respiratory organs. Amphibian may respire by gills, skin or lungs. 3 or 4 chambered heart present. They are divided into 4 classes: Class 2: Amphibia Amphi-dual; bios-life. Dual … Read more