7 public questions tagged with this topic.
Insects constitute more than 70% of all described animal species, making them the most species-rich animal group.
Ref: NCERT Class 12 Biology Chapter 13: Biodiversity and Conservation Species-Area Relationship
Ovoviviparous animals, such as some sharks, retain eggs inside the female's body until hatching.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Vertebrata - Aves and Mammalia
Hydra, a cnidarian, is diploblastic, meaning its body develops from two germ layers: ectoderm and endoderm.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Porifera and Cnidaria
In plants, classes with a few similar characters are assigned to the higher category called division. In animals, the corresponding category is phylum.
Ref: NCERT Class 11 Biology Chapter 1: The Living World Taxonomic Categories - Family Order Class Phylum Kingdom
Domain Eukarya encompasses all organisms possessing true membrane-bound nucleus enclosing linear chromosomes complexed with histones, plus endomembrane system including endoplasmic reticulum, Golgi, and mitochondria or derived hydrogenosomes. Membership includes diverse protistan lineages, green plants deriving from primary endosymbiosis of cyanobacterium, multicellular fungi with absorptive nutrition and chitinous walls, and animals with collagen, nervous systems, and embryogenesis. Unified by eukaryotic signature proteins such as ubiquitin, spliceosome, and actin-tubulin cytoskeleton, molecular phylogeny places protists as grade leading to other kingdoms, yet all belong within single eukaryotic domain distinct from prokaryotes.
Ref: Campbell Biology 12th ed., Chapter 26 Domain Eukarya includes protists plants fungi animals; OpenStax Biology Eukarya diversity
A large bear retains body heat more effectively than a small bird, lizard, or amphibian because body size lowers the surface-area-to-volume ratio. Heat is produced throughout metabolically active tissue, which scales broadly with mass, but exchanged with the environment across body surface. As size increases, surface area grows more slowly than volume, so less heat is lost per unit mass. Bears also possess fur and subcutaneous fat that reduce conduction and convection. Birds are endothermic and insulated by feathers, but a small bird has high relative surface area and must sustain a very high mass-specific metabolic rate to remain warm. Desert lizards and amphibians rely mainly on environmental heat and typically do not maintain the same internally generated thermal gradient; amphibian skin can additionally promote evaporative cooling. Physiological state and habitat matter—a torpid bear produces less heat, and feathers can be exceptionally effective—but the geometric comparison strongly favours the large bear for retention. This principle helps explain why many cold-region endotherms are large and compact and why small endotherms require frequent feeding to offset rapid heat loss.
Ref: Evolutionary Analysis, Herron & Freeman, 5th Ed., Ch. 10
reflex actions represent a crucial and fascinating evolutionary adaptation. A reflex is a sudden, involuntary reaction to a potentially harmful stimulus. The specific pathway taken by the nerve impulses in a reflex action is called a reflex arc. Because the conscious thinking process of the brain is relatively slow and involves complex interactions of many millions of neurons, reflex arcs have evolved to facilitate immediate responses. If we were to consciously think about pulling a hand away from a hot object, we might get burnt before the thought process completes. Therefore, reflex arcs are formed in the spinal cord, where incoming sensory nerves meet outgoing motor nerves, allowing the signal to safely bypass the brain for a rapid, life-saving response, while still sending a message to the brain for later processing. Thus, they evolved specifically because the brain's detailed thinking process is simply not fast enough to prevent immediate harm.
Ref: NCERT Class 10 Science chapter 6 control and coordination
