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The latest Messages 37
2021-11-12 21:13:45
NON-CHORDATES ENDED NOW CHORDATES HERE IS
𝘾𝙇𝘼𝙎𝙎 𝘼𝙈𝙋𝙃𝙄𝘽𝙄𝘼:-
The characteristics of the organisms present in class amphibia are as follows:
These can live both on land and in water.
They are ectothermic animals, found in a warm environment.
Their body is divided into head and trunk. The tail may or may not be present.
The skin is smooth and rough without any scales, but with glands that make it moist.
They have no paired fins. Unpaired fins might be present.
They have two pairs of limbs for locomotion.
They respire through the lungs and skin. Gills might be present externally in some adults.
The heart is three chambered.
The kidneys are mesonephric. The excretory material includes ammonia and urea.
They possess ten pairs of cranial nerves.
The lateral line is present during their development.
The sexes are separate and fertilization is usually external. However, in salamanders, the fertilization is internal.
Development is indirect with metamorphosis.
Breeding occurs in water. The copulatory organs are absent in males.
Eg., Frogs, Salamanders
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219 views18:13
2021-11-12 16:27:30
> Photosynthesis In Higher Plants
> Class 11th Biology
> @Science_Wallah
88 views13:27
2021-11-11 19:42:44
𝙋𝙃𝙔𝙇𝙐𝙈 𝙃𝙀𝙈𝙄𝘾𝙃𝙊𝙍𝘿𝘼𝙏𝘼:-
Hemichordata (Hemi – half; chordata- notochord) was earlier placed as a sub-phylum under Phylum-Chordata. But, now it is considered as a separate phylum under Non-chordata. These are also called half chordates. This phylum consists of a small group of worm-like animal.
General Features
Some important general features of phylum—hemichordata are discussed below:-
i. Habit and Habitat They are exclusive marine and mostly live in burrows.
ii. Symmetry and Body Organisation They are bilaterally symmetrical and triploblastic. They have organ system level of organisation.
iii. Body Form They are soft-bodied, cylindrical and unsegmented body is divisible into proboscis, collar and trunk. The body cavity is true coelom.
A true notochord is absent.
iv. Digestive Systems Digestive system is complete.
v.Respiraton Respiration occurs through several pair of gill slits or through the general body surface.
vi. Circulatory System It contains a dorsal heart and is open type.
vii. Excretory system It consists of proboscis gland.
viii. Nervous system It is primitive, consists mainly of an intraepidermal nerve plexus.
ix. Sensation Sensory cells of the epidermis act as sense organs.
x. Reproduction It is mostly sexual. Sexes are separate. Development is indirect with tornaria larva.
is the connecting link between echinoderms and chordates.
e.g., Balanoglossus (acorn or tongue worm), Saccoglossus, Cephalodiscus, etc.
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173 views16:42
2021-11-11 16:20:20
Revision in one short imp topic biological classification
Viruses
The viruses are acellular structures and therefore do not find a place in Whittaker’s five kingdom classification. They consist of nucleic acid (either DNA or RNA) that is surrounded by a protein coat. These viruses can grow and multiply only within a host cell. Viruses exist as crystals outside the host cell. They cause disease and severely damage the host. Examples of common viruses are the viruses that cause cold, flu, polio, AIDS, etc.
Viroids
They are the smallest known infectious structures and consist only of nucleic acid without a protein shell.
Lichens
They are known to be the symbiotic associations of algae and fungi. The pair of algae are autotrophic and synthesized and provide food. The mushroom pair offers protection and shelter.
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156 views13:20
2021-11-10 22:16:56
𝙋𝙃𝙔𝙇𝙐𝙈 𝙀𝘾𝙃𝙄𝙉𝙊𝘿𝙀𝙍𝙈𝘼𝙏𝘼:-
Phylum—Echinodermata (Echinos—spines; derma—skin) includes the spiny skinned animals, which are exclusively marine. Jacob Klein (1734) coined the term ‘Echinodermata’. It includes about 6,000 species.
General Features
Some important generalfeatures of phylum—echinodermata are discussed below:-
i. Habit and Habitat These are marine forms and are bottom dwellers.
ii. Symmetry The adults have radial (pentamerous) symmetry but, the larval forms have bilateral symmetry.
iii. Germ Layers and Organisation They are triploblastic and exhibit organ system grade of organisation.
iv. Head It is absent in echinoderm and body also lacks segmentation.
v. Body Cavity They have true coelom, which is lined by a ciliated peritoneum. The most distinctive feature is the presence of water vascular system or ambulacral system with tube feet that help in locomotion, capture of food and respiration.
vi. Endoskeleton It contains numerous calcareous plates called ossicles beneath the skin.
vii. Locomotion The locomotion is carried out by tube feet.
viii. Digestion The digestive tract is simple and complete type. The mouth is present on the lower side and the anus is on the upper side.
ix. Respiration It occurs through tube feet, which help in respiration.
x. Circulation It is reduced and open type called as haemal system.
Xi.Excretion The excretory organs are absent. The waste products are removed by diffusion through branchiae or amoebocytes.
xii. Nervous System It contains circum-oral nerve ring, transverse and radial nerves.
xiii. Reproduction Echinoderms reproduce sexually. Sexes are separate and show no sexilal dimorphism. Fertilisation is external and development is indirect.
e.g., Asterias, (sea star or star fish), Ophiura (brittle star). Echinus (sea urchin),Cucumaria (sea cucumber), Antedon (feather star).
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219 views19:16
2021-11-10 19:22:47
Spongilla Structure and Characteristics
Spongilla are found in freshwater, lakes and slow streams. They get attached to submerged plants, logs and sticks.
They may be branched or unbranched and have numerous Ostia present all over the surface.
The colour varies from light yellow to green. It depends on the amount of zoochlorella, a green alga (symbiotic association).
The outer surface is soft textured and supported by a skeleton of spicules, spongin fibres or both. Spicules may be simple, siliceous or tetraxial.
The canal system is leuconoid type. It is a complex system of interconnected canals, which lead to irregular symmetry to Spongilla. In the larval form, rhagon type of primitive canal system is found.
Water goes inside through Ostia and to incurrent canals. Incurrent canals open into flagellated chambers, which are lined by choanocytes. Flagellated chambers open into the excurrent canal and then water flows outside from osculum.
Excurrent canals are formed by extensive division and shrinkage of spongocoel.
Gaseous exchange and excretion is by diffusion.
They feed on small organic particles. Many insects feed on them.
They reproduce sexually as well as asexually.
Asexual reproduction is by budding or forming gemmules. Gemmules are formed during adverse conditions, which on the return of favourable conditions, germinate.
Spongilla are hermaphrodite. Each sponge produces both egg and sperm. Sperm of one sponge reaches to the Ostia of another sponge and after developing inside the cavity, free-swimming larvae are born.
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182 viewsedited 16:22
2021-11-09 17:36:23
𝙋𝙃𝙔𝙇𝙐𝙈 𝙈𝙊𝙇𝙇𝙐𝙎𝘾𝘼:-
The phylum—Mollusca (Molluscs — soft bodied) includes the soft bodied, unsegmented, eucoelomate animals. These are called molluscs or shelled animals. Johnston (1650) coined .the term ‘Mollusca’. Mollusca is the second largest animal phylum and includes about 85,000 species.
The study of molluscs is called ‘Malacology’.
General Features
Some important general features ofphylum—mollusca are discussed below:-
i. Habit and Habitat Molluscs are mostly of marine forms (Sepia, Octopus, Chiton, etc.) Some are freshwater (e.g, Unio and Pila) and some are also terrestrial forms (e.g, Land snails). Few molluscs are parasites also, e.g., Glochidium larva, etc.
ii. Symmetry These are generally bilaterally symmetrical and some are asymmetrical due to torsion or twisting during growth.
iii. Germ Layers and Organisation They are triploblastic and possess organ system level of organisation.
iv. Body Form They have unsegmented, soft body covered by a calcareous shell, which is differentiated into head, muscular foot and visceral hump.
Mantle is a soft, spongy thick fold of skin over the visceral hump that secretes calcareous shell. The space between the hump and the mantle is called the mantle cavity in which feather like gills are present.
v. Skeleton Molluscsgenerally have shell as exoskeleton. In Octopus, shell is absent.
vi. Body Cavity The coelom is greatly reduced although they are eucoelomate.
vii. Locomotion The locomotory organ is muscular foot.
viii. Digestion The digestive tract is complete. The mouth contains a rasping organ called radula with file like transverse row of chitinous teeth. Anus opens into the mantle cavity.
ix. Respiration In terrestrial forms respiration occurs through lungs. In aquatic forms, respiration occurs through feather-like gills or ctenidia.
X.Excretion A pair of metanephridia (kidneys) or organs of Bojanus or Keber’s organs are present.
xi. Circulation Open type of circulation is present. The coelom is called haemocoel.
xii. Sense Organs These have eyes, statocyst, tentacles for equilibrium and receptors for touch, smell and taste.
xiii. Nervous System Few pairs of ganglia like cerebral, visceral and pedal with nerves is present.
xiv. Reproduction Molluscs reproduce sexually. Sexes are separate and mostly oviparous. Fertilisation is external or internal.
Development is either direct or indirect with larval stages like trochophore, glochidium and veliger. e.g., Chaetopleura(chiton), Dentalium (elephant tusk shell), Pila (apple snail), Patella, Aplysia (sea hare). Pinctada (pearl oyster) Sepia (cuttlefish), Loligo (squid), Octopus (devil fish).
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76 views14:36
2021-11-08 20:33:26
𝙋𝙃𝙔𝙇𝙐𝙈 𝘼𝙍𝙏𝙃𝙍𝙊𝙋𝙊𝘿𝘼:-
Phylum-Arthropoda (Arthron – jointed; podos — foot) include the first and simplest segmented animals. These are commonly called as jointed legged animals. It is the largest group of animal that include about 1,000,000 insect species, 1,02,248 spiders and scorpion species, 1,03,248 arachnoid species and 47,000 crustacean species representing about 80% of total known animal species.
General Features
Some important general features of phylum—arthropoda are discussed below:-
i. Habitat and Habit They may be aquatic or terrestrial. They may occur as free-living or parasitic forms e.g., Bed bugs, ticks, mosquitoes, etc.
ii. Body Parts Body is segmented externally. It has distinct head, thorax and abdomen. Head bears many fused segments and sense organs.
iii. Symmetry and Body Organisation Arthropods are bilaterally symmetrical. They are triploblastic with organ system level of organisation.
iv. Appendages They have jointed, paired appendages, which are present in some or all somites or segments. These perform various functions like walking, clinging, jumping, feeding, etc.
v. Exoskeleton The exoskeleton is formed of thick, tough and non-living chitinous cuticle.Exoskeleton protects animal from mechanical and chemical injuries, prevents desiccation and also helps in attachment.
vi. Locomotion Jointed appendages help in locomotion. Cilia are found to be absent in arthropod.
vii. Digestive System Alimentary canal is complete and well-developed, i.e., divided into foregut, midgut and hindgut.
viii. Respiration It occurs through general body surface, gills (e.g., Prawn), book lungs (e.g., Scorpion and spider), trachea (e.g., cockroach) and book gills (e.g., King crab).
head tall Antenna.
IX. Circulation The circulatory system is open type, i.e., blood flows in the haemocoel instead of blood vessels.
x. Excretion The excretory organs are Malpighian tubules (opening into duct) or green glands opening ‘ directly to the exterior.
xi. Nervous System The nervous system consists of a nerve ring and a double ganglionated ventral nerve cord.
xii. Sense Organs Arthropods have simple eyes called ocelli and compound eyes. Aquatic forms have statocysts for balancing.
xiii. Reproduction Arthropods reproduce by sexual methods. Fertilization is usually internal type. They are generally oviparous but few are viviparous, i.e., scorpion. Development may be direct or indirect involving metamorphosis.
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43 views17:33
2021-11-07 21:17:10
𝙋𝙃𝙔𝙇𝙐𝙈 𝘼𝙉𝙉𝙀𝙇𝙄𝘿𝘼:-
Phylum—Annelida (Annulus — ring; lidos — form) includes segmented worms. The&term ‘Annelida’ was first coined by Lamarck (1809). It includes about 12,000 species of animals.
General Features
Some important generalfeatures of phylum- annelida are discussed below:-
i. Habit and Habitat They may be aquatic, terrestrial and free-living or parasitic.
ii. Body Wall The outermost covering of body is thin and moist cuticle secreted by the epidermis.
iii. Metamerism The body is divided into segments or metameres by ring like grooves-the annuli. It is called metameric segmentation. The segmentation is external as well as internal.
iv. Symmetry Annelids are bilaterally symmetrical.
v. Germ Layers They are triploblastic animals.
vi. Organisation and Body Plan They show organ system level of organisation and tube within a tube body plan.
vii. Cephalisation These show true cephalisation.
viii. Body Cavity Annelids have true coelom (eucoelomates). It is formed by splitting of mesodermal epithelium and such a coelom is called as schizocoelom.
ix. Skeleton The coelomic fluid in the body cavity acts as hydrostatic skeleton for the animal.
x. Locomotion Annelids move by paired, lateral, hollow, fleshy, appendages in each segment called parapodia or chitinous setae. Aquatic annelids like Nereis possess lateral appendages that help in swimming and have longitudinal and circular muscle for locomotion.
xi. Digestive System The digestive tract is straight and complete, starting from mouth and ending at anus.
xii. Respiration It occurs through skin, gills or parapodia.
xiii. Circulatory System They are first animals that have a closed circulatory system, i. e., the blood flows through a system of blood vessels.
Excretory System The excretory organs are nephridia in each segment, which helps excretion and osmoregulation.
Nervous System It contains a nerve ring around the pharynx and a double ventral nerve cord with ganglia.
Reproduction Annelids reproduce sexually. They are unisexual, e.g., Nereis or bisexual (hermaphrodite),
Hirudinaria.
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165 views18:17
2021-11-07 11:33:38
𝘼𝙉𝙄𝙈𝘼𝙇 𝙆𝙄𝙉𝙂𝘿𝙊𝙈 𝙉𝙊𝙏𝙀𝙎:-
Disease Caused by 𝘼𝙨𝙘𝙝𝙚𝙡𝙢𝙞𝙣𝙩𝙝𝙚𝙨:-
Aschelminthes may cause the following diseases in humans
(i) Ascaris lumbricoides or giant intestinal roundworm is an endoparasite of the small intestine of humans. It causes ascariasis.
(ii) Wuchereria (filaria) or filarial worm is an endoparasite in the lymphatic vessels and lymph nodes of humans. It causes elephantiasis in the legs, arms, scrotum, etc.
(iii) Ancyclostoma duodenale or hookworm is an endoparasite in the small intestine of humans. It causes ancylostomiasis disease.
(iv) Loa loa the eyeworm lives in subdermal connective tissue of man. It causes loiasis disease characterised by subcutaneous smelling mosdy around the eyes.
(v) Enterobius or pinworm is found in caecum, colon or vermiform appendix of humans.
(vi) Trichinelia or trichina worm is found in small intestine of human beings and some other mammals like pigs, domestic animals are rodents. It causes trichinellosis.
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192 views08:33
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