Adaptive radiation


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Adaptive radiation refers to the expansion and diversifications of an evolving group of an organisms as they adapt to new ecological niches. A simple definition of adaptation is “the good fit of organisms to their environment. INTRODUCTION

Types of adaptations:

Physiological adaptation Protective adaptation Structural adaptation Animal association Types of adaptations

Physiological Adaptation:

Feeding & digestion More oxygen Energy metabolism Thermo regulation Feeding &digestion: ingestion of food is feeding. D igestion is the breakdown of complex molecules into simpler molecules.Animal have adaptations to suit the feeding and digestion process. Physiological Adaptation

Protective Adaptation:

Coloration mimicry Crptic color resemblances changing color batesian mullerian concealing signals Recognition warning Protective Adaptation

Protective adaptation:

COLOURATION: Animal colors can be produced by 2 ways. P igments that absorb certain wavelength of sunlight and reflect others produce chemical colors. animals derive color from sunlight, some produce chemical light of their own-Bioluminescence. The ability to change color is metachrosis and the special cells responsible for it is chromatophores. CRYPTIC: When overall coloration of an animal matches that of the background and becomes well camouflaged ,it is called cryptic or concealing coloration. The animal escapes from the enemies (protective coloration) or waits to catch prey successfully (aggressive coloration) by cryptic coloration. E.g.. Snow animals are white. F orest animals are striped/spotted and desert animals are sandy in color. COLOR RESEMBLENCE: Animals resembles the objects in the surrounding .E.g.. Fishes living in the seaweed often have leafy outgrowths of the body surface. Protective adaptation

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Changing colors: certain animals change color rapidly. The color change maybe seasonal or ecological or during reproductive phase. Calotes produces red color in the neck region of the male during reproductive season. Alluring: the coloration is adapted by predators to attract and capture they prey. spiders exhibit this. Signals: protective colors that helps in either recognition or warning.

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Variable colors: Alluring

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WARNING: also called somatic colors used for warning the spot on the electric ray TORPEDO are advertising the awaiting dangers of an electric shock. MIMICRY: A protective resemblance of animal to inanimate object or the simulation for itself. P rotection of a harmless species by mimicking an organism, in form, appearance, color and behavior of another species that is dangerous. Batesian: It’s a simple type of warning mimicry. eg.north American viceroy butterfly resembles the high distasteful monarch butterfly in this pair the mimic is viceroy and is highly palatable .MULLERIAN: it was given by firtz Muller. He suggested that, by sharing same pattern each species profits from the predators early experience with any of the pair. eg.ctenuchid moth resembles a wasp where both of them are unpalatable. CONCEALING: ferocious predators for aggression adopt this mimicry. E.g. south America leaf fish is only 3 inches long and perfectly copy a dead leaf in shape and color. scorpion fish appear like a lump of coral but if a fish comes neat them they catch it with surprising speed.

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Warning mullerian


Structural adaptations refers to the modifications of body parts and contour, which suits best life conditions. 1.cursorial adaptation 2.fossorial adaptation 3.scansorisl adaptation 4.desert adaptation 5.aquatic adaptation 6.volant adaptation STRUCTURAL ADAPTATION

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Cursorial adaptation: this is seen in the terrestrial animals living in open planes or in grasslands. Essential features-body needs necessary support during locomotion much of the body should from ground, regulations of directions should be maintained during running. Adaptive characters: Body contour- stream lined with compressed thorax, flattened ribs, backwardly thrown external ears; change in foot posture-speed is related to structure of propelling organs limbs, primitive type of foot is plantigrade (entire palm on ground during locomotion. Eg. Bear, man) ,Digitigrade (help in walking or running on digits eg.dogs and birds), Unguligrade (animals move on nails which are modified as horses and cattels); bipedality (walking or runniing with two legs – hind limbs are exclusive locomotory organ, fore limbs help in food capture, resting on ground etc.)

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2.Fossorial- modifications allow an animal to climb for digging eg. swine, elephants, they dig soil in search of food. tusk and snout act as digging devices, the fossorial animals live permanent subterranean life (living below the earth surface) Adaptations-spindle shaped body offers little resistance to subterranean passage, short tail, modified limbs for digging, eyes reduced. 3.Scansorial adaptation- modifications allow an animal to climb on vertical surface and leads successful life in trees. scansorial refers to adaptation for Wall and rock climbers (geckos), rodents, insectivores. Adaptations- strengthening of chest girdle, limbs and ribs, elongation and movable limbs, claws for climbing(cat), joint fingers.

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Scansorial adaptation of geckos

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4.Desert adaptations- desert is a vast arid zone of and devoid of vegetation. E xtreme climate condition, shortage of food and every day struggle is common. Both plants and animals exhibit modifications so that they can survive. Adaptations- against scarcity of water: obtain water by eating succulent plants (desert,rabbit,wood rat), storage of water in body cells (camels); conserve water by reducing evaporation (thick skin). Against extreme temperatures long legs for lifting the body from burning sand and long external ears for heat radiation. Against sand storms-protected eye, ear opening and nostrils; for swift movement-well developed hind limbs and tails etc. for defense- spinescence (dry and hard covering of the body studded with spines e.g.. Horned toad,coloration,unpleasant odors etc.

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5.aquatic- water allows aquatic animals some advantage over terrestrial animals-available in large amount, migration and escape from danger is easy, rich resource for food availability. Adaptations: stream-lined body tapering backward, no protuberance of body except fins region for swift movement; presence of accessory respiratory organs and swim bladder ; gills as chief respiratory organ; presence of large eyes, internal ears, lateral line sense organs for sensory functions. Volant adaptation- organisms capable of moving in air are modified for aerial life. These animals have modifications according to their environment. Advantages- flying allows easy search suitable for feeding and resting, easy escape from predator. Adaptations- flying fishes are good gliders and during gliding fins are fully stretched. Specialized organ for flight is bird’s wing(modified forelimbs).there are different types of wings 1.high speed wing- (generate much speed seen in ducks and humming birds) 2.long soaring wing- (allow rapid soaring seen in sea birds, albatross) 3.broad soaring wing- (help in sloe soaring take off and descend in a relatively small area eg; eagles)

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Volant adaptation

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Three types of flights seen in birds- flapping (continuous beating of wings e.g.; pigeon and crow) Hovering- (rapid beating of wings so that bird can remain in air for long period;eg.humming bird) Soaring-(prolonged sailing in air without beating of wings this helps to save energy for flapping; hawks and vultures. Adaptations: reduction in bone weight, cranial bones are paper like without sutures; presence of pneumatic bones; absence of teeth, feathers for flight; many internal organs such as gall bladder, urinary bladder, oviduct larger heart, and air sacs for balance etc.


Animal association between organisms exists for getting food, protection, and defense, division of labor etc. Aggregation: association of gregarious animals belonging to same species for mutual aid, either defense or securing food. except leadership in some cases, there is no division of labor in aggregation. Fishes are example of the aggregations. Communalism: in this association, division of labor is seen; often referred as social Insects, and honeybees. The members perform functions like foraging or collecting food. Symbiosis: interaction between 2 organisms. In this three types of interactions occur 1.mutualism 2.commensalism 3.parasitism ANIMAL ASSOCIATION

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Mutualism: both the organism involved in the interaction is benefited.On separation the organism will Ants and aphids- ants obtain exudation (called milk) from the aphids, which in return gets food protection and care from the ants. Commensalism- one organism is benefited and other is not benefited nor harmed.When separated the organism can association between sea anemone and hermit crab. Parasitism- one organism is benefited and the other is Parasite plasmodium causes hypertrophy or increase in cell size of RBC in man. The organism exhibit modifications for parasitic life sucking organs , lack of locomotory organs and secretion of lytic solutions etc.

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Conclusion: adaptation is “any aspect of an organism that promotes its welfare (or the general welfare of the species to which it belongs) in the environment it usually inhabits” Modifications of morphology, physiology or behavior of an organism that enable it to thrive successfully in a particular environment.

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REFERENCES: Strickberger W.M- Evolution-Jones&Bartlet publishers, Boston, 2005 P.S.Verma, V.K.Agarwal -Evolution and Ecology- S. Chand & company ltd. New Delhi, 2005. Ridley M.-Evolution- 2 nd edition; Pearson Education, India, 2002. Olson, M. E. and A. Arroyo-Santos. 2009. Thinking in continua: Beyond the “adaptive radiation” metaphor. Bio Essays 31: 1337–1346 . Simpson, G. G. 1953. The Major Features of Evolution. Columbia University Press, New York.

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