Biology in the living world is composed of a lot of fascinating exceptional creatures. Here, let us look at some exceptional topics in the biological world for the NEET exam covered under the class 11 and 12 syllabus.

Table of Contents:

• Biological Classification
• Plant Kingdom
• Animal Kingdom
• Morphology of Flowering Plants
• Anatomy of Flowering Plants
• Cell – The Unit of Life
• Biomolecules
• Body Fluids and Circulation
• Locomotion and Movement
• Neural Control and Coordination
• Reproduction in Organisms

Biological Classification

• Archaebacteria – They belong to the kingdom Monera and are classified as bacteria due to their resemblance to bacteria under a microscope. The structure of their cell wall is different from other bacteria. The cell wall of bacteria is made up of peptidoglycan whereas the cell wall of archaebacteria is made of pseudopeptidoglycan.
• Euglena – Euglena are unicellular eukaryotes found in salt and freshwater. They are exceptional organisms showing both plant and animal characteristics. They lack cell walls (like animals) and also have chloroplast (like plants).

Plant Kingdom

• Red Algae – They are mostly found in deep water and are considered as an exception in the plant kingdom. They contain a red photosynthetic pigment called phycoerythrin that can absorb blue light, which can penetrate deeper than any other light wave.
• Life Cycle of Algae – Generally most genera of algae are haplontic in nature. Their dominant stage is a haploid gametophyte. But there are some exceptions where haplo-diplontic and diplontic algae are also present.The diplontic life cycle is dominated by a diploid sporophyte, whereas in haplo-diplontic, both diploid and haploid stages are multicellular. The Haplo-diplontic life cycle is seen in kelp and Ectocarpus and Diplontic is seen in Fucus.

Also Check:MCQs on Algae

Animal Kingdom

Similar to the plant kingdom, the animal kingdom also has some exceptional creatures.

• Lungfish – Generally fishes have a two-chambered heart consisting of one atrium and one ventricle. Lungfish (order Dipnoi) is an exception where the atrium is partially divided into two chambers by the presence of numerous pectinate muscles. Examples – Protopterus, Lepidosiren and Neoceratodus.
• Paedogenesis – Larval stage is the juvenile stage where the organisms cannot reproduce. But the Axolotl larva of American tiger salamanders can reproduce. This phenomenon is called neoteny or paedogenesis.
• Crocodiles – Reptiles typically have a three-chambered heart but crocodiles are the only reptiles to have a four chambered heart (two atria and two ventricles). Also all crocodilians like alligators, crocodiles, gharials and caimans have a four chambered heart like mammals.
• Flightless Birds – Generally birds can fly but Ostrich, Kiwi, Emu and Penguin are exceptions. Dodo is an extinct variety of flightless bird.
• Mammals – Mammals are usually viviparous with exceptions being duck-billed platypus (Ornithorhynchus) and spiny anteaters (Echidna). They are monotremes and are the only extant mammals to lay eggs.
• Likewise, mammals are usually terrestrial, fossoreal or arboreal. But some mammals are aquatic like whales and seals. Bats are also an exceptional animal as they are the only mammals capable of true flight.
• Vertebrate with colourless blood – Vertebrates like mammals, fish, birds, reptiles and amphibians have red blood with haemoglobin to transport oxygen. Antarctic blackfin icefish is the only known vertebrate that lacks red blood cells containing haemoglobin. It is also called white-blooded fish.

Morphology of Flowering Plants

• Reticulate Venation in Monocot Leaves – Generally monocot leaves show parallel venation. But reticulate venation is also observed in monocots like Colocasia esculenta and Smilax zeylanica. Likewise, dicots show reticulate venation. As exceptions, parallel venation is seen in Calophyllum inophyllum and Eryngium yuccifolium.
• Monocots are endospermic, but orchid seeds and alisma seeds are non-endospermic monocots.
• Roots – Generally roots are geotropic. But mangrove roots are negatively geotropic (grows up and away from ground). This type of aerial root is seen in mangroves like Rhizophora, Avicennia and Sonneratia. Similarly, most of the roots are generally non-green and non-photosynthetic. But Tinospora shows green and photosynthetic roots. There are also flowering plants with no roots such as Utricularia stellaris and Wolffia arrhiza.
• Dicot plant without cotyledons – Cuscuta reflexa is a parasitic plant without cotyledons.

Anatomy of Flowering Plants

• Plant cell without nucleus – Sieve tubes that are specialised for transport have no nuclei. Each sieve tube has a perforated end such that its cytoplasm connects one cell to the next. They also lack ribosomes and thus need a companion cell for transportation.

Cell – The Unit of Life

• Mycoplasma – All prokaryotes except Mycoplasma (genus of bacteria) have a cell wall surrounding the cell membrane.
• Mesosomes – Mitochondria are the respiratory organelles of most organisms. In prokaryotes, mesosomes perform the function of mitochondria. Likewise, mitochondria and chloroplasts also have some prokaryotic features like the 70s ribosomes and circular DNA molecules.

Biomolecules

A bacteriophage is a double-stranded DNA virus that infects and replicates within a bacteria. Single-stranded DNA is also found in bacteriophages like M-13 and φ × 174.

Body Fluids and Circulation

• Arteries and Veins – Most arteries and veins carry oxygenated blood and deoxygenated blood respectively. The exceptions here are the pulmonary artery and umbilical artery that carries deoxygenated blood to lungs and placenta respectively. Also, the pulmonary vein and umbilical vein carries oxygenated blood to the heart.
• Red Blood Cells – Mature RBCs in mammals are the animal cells devoid of nucleus. RBCs or erythrocytes of mammals are circular and biconcave in nature. But Camels and Llamas have oval and flat RBCs as an exception.

Locomotion and Movement

• Syncytial Cells – A syncytium is a single cell that contains multiple nuclei as a result of multiple cell fusions. In humans, syncytia can be found in skeletal muscles, cardiac muscles, smooth muscles, placenta, etc.
• Floating Ribs – The ribs are directly or indirectly attached to the sternum. As an exception, the 11th and 12th pairs of ribs are not connected to the sternum directly or indirectly. They are termed floating ribs.

Neural Control and Coordination

An ideal exception in the neural system of humans is the nerve cells. The nerve cells cannot form centrosome and spindle fibres. Thus, unlike most animal cells, the neurons or nerve cells are incapable of cell division.

Reproduction in Organisms

Usually, the young ones are produced by the fertilisation of eggs with the help of sperms. Whereas drones in honey bees develop from unfertilised haploid eggs of the queen bee. Also, the only role of a drone is to fertilise a receptive queen.

Check BYJU’S NEET for more such interesting and important concepts related to the NEET exam.

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