Convergent Evolution - Definition and Examples | Biology Dictionary
How do adaptations increase the organism's ability to survive? What is the relationship between evolution and biodiversity? . cane toads in Australia; prickly pear distribution in Australia define and explain convergent and divergent evolution; analyse an example of divergent evolution in the Galapagos, eg iguanas. A widespread example of convergent evolution is the evolution of which belong to a different class of organism and therefore niches in Australia and the surrounding islands; this history. A small mantispid and a preying mantis, an example of convergent evolution. It culminates in unrelated organisms with similar morphological characteristics may represent a "missing link" in the evolution of flowering plants, but others say that of the independent evolution of a given phenotype can be described with a .
Flightless birds such as the emu, ostrich, and rhea fill very similar ecological niches on different continents. If ratites evolved from a Gondwanan common ancestor, they would not represent evolutionary convergence but instead would constitute an example of a shared and conserved ancestral flightless state.
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- Convergent Evolution in Desert Lizards
Now thought to be convergent, DNA evidence suggests that these "ratites" do not share a common ancestry but have evolved independently. Live bearing, or viviparity, has evolved over times among squamate reptiles lizards and snakes Blackburnusually in response to cold climates. The probable mechanism behind the evolution of viviparity is that, by holding her eggs, a gravid female can both protect them from predators and, by basking, warm them, which would increase rate of development.
Eventually, such selective forces favoring egg retention could lead to eggs hatching within a mother and live birth Huey This has happened even in geckos, all of which lay eggs except for one genus in New Caledonia and several related cold temperate New Zealand forms, which bear their young alive.
In some skinks and xantusiid lizards, embryos attach to their mother's oviducts and grow, gaining nutrients during development via placental arrangements reminiscent of those in mammals.
Thorny Devil Moloch horridus Horned Lizard Phrynosoma cornutum Convergent evolutionary responses of lizards to arid environments are evident between continents. For example, Australian and North American deserts both support a cryptically-colored and thornily-armored ant specialized species: No Kalahari lizard has adopted such a life style. Interestingly, morphometric analysis demonstrates that the thorny devil and desert horned lizard are actually anatomically closer to one another than either species is to another member of its own lizard fauna, which are much more closely related Pianka Emerald Tree Boa Corallus caninus Green tree python Chondropython viridis Emerald Tree Boas from South American Amazonian rainforests are strikingly convergent with Green Tree Pythons found halfway around the world in similar rainforests in Australia, a spectacular example of ecological equivalents.
Both of these snakes live high up in the canopy and eat birds. Adults are green, cryptically colored, matching the colors of leaves. Juveniles of both species are bright yellow or orange. Juvenile Emerald Tree Boa Blue-tailed anguid from Mexico Celestes A skink Morethia butleri from Australia Colorful, blue, red and yellow tails have evolved repeatedly among distantly related lizards in many families agamids, anguids, gymnopthlamids, lacerids, skinks, and teiidspresumably a ploy to attract a predator's attention away from the head to the tail, which can be broken off and regenerated should a predator attack it.
The New World iguanid Basiliscus, sometimes called 'Jesus lizards,' because they can run across the surface of water, have undergone convergent evolution with the Old World agamid Hydrosaurus. Both Basiliscus and Hydrosaurus have enlarged rectangular, plate-like, fringed scales on their toes, which allow these big lizards to run across water using surface tension for support.
Open sandy deserts pose severe problems for their inhabitants: Even so, natural selection over eons of time has enabled lizards to cope fairly well with such sandy desert conditions. Subterranean lizards simply bypass most problems by staying underground, and actually benefit from the loose sand since underground locomotion is facilitated.
Burrowing is also made easier by evolution of a pointed, shovel-shaped head and a countersunk lower jaw, as well as by small appendages and muscular bodies and short tails. Such a reduced-limb adaptive suite associated with fossorial habits has evolved repeatedly among squamate reptiles in both lizards and snakes Weins and Slingluff During the hours shortly after sunrise, but before sand temperatures climb too high, diurnal lizards scurry about above ground in sandy desert habitats.
Sand specialized lizards provide one of the most striking examples of convergent evolution and ecological equivalence. Representatives of many different families of lizards scattered throughout the world's deserts have found a similar solution for getting better traction on loose sand: A skink, Scincus, appropriately dubbed the 'sand fish,' literally swims through sandy seas in search of insect food in the Sahara and other eastern deserts.
These sandy desert regions also support lacertid lizards Acanthodactylus with fringed toes and shovel noses. Far away in the southern hemisphere, on the windblown dunes of the Namib desert of southwestern Africa, an independent lineage of lacertids, Meroles formerly Aporosaura anchietae, has evolved a similar life form. In North America, this body form has been adopted by members of the iguanid genus Uma, which usually forage by waiting in the open and eat a fairly diverse diet of various insects, such as sand roaches, beetle larvae and other burrowing arthropods.
They also listen intently for insects moving buried in the sand, and dig them up. Sometimes they dash, dig, and paw through a patch of sand and then watch the disturbed area for movements. Meroles Aporosaura anchiete Toes of Uma scoparia All of these lizards have flattened, duckbill-like, shovel-nosed snouts, which enable them to make remarkable 'dives' into the sand even while running at full speed.
The lizards then wriggle along under the surface, sometimes for over a meter. Biologists sometimes define two types of evolution based on scale: Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups. Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.
Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups. The evidence for evolution In this article, we'll examine the evidence for evolution on both macro and micro scales. First, we'll look at several types of evidence including physical and molecular features, geographical information, and fossils that provide evidence for, and can allow us to reconstruct, macroevolutionary events.
At the end of the article, we'll finish by seeing how microevolution can be directly observed, as in the emergence of pesticide-resistant insects. Anatomy and embryology Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations.
He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor. Branching diagram that appeared in Charles Darwin's On the origin of species, illustrating the idea that new species form from pre-existing species in a branching process that occurs over extended periods of time.
In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor.
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We can use this idea to "work backwards" and figure out how organisms are related based on their shared features. Homologous features If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor.
Physical features shared due to evolutionary history a common ancestor are said to be homologous. To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside.
That's because they're adapted to function in different environments. However, if you look at the bone structure of the forelimbs, you'll find that the pattern of bones is very similar across species.
It's unlikely that such similar structures would have evolved independently in each species, and more likely that the basic layout of bones was already present in a common ancestor of whales, humans, dogs, and birds.
The similar bone arrangement of the human, bird, and whale forelimb is a structural homology. Structural homologies indicate a shared common ancestor. Some homologous structures can be seen only in embryos. For instance, all vertebrate embryos including humans have gill slits and a tail during early development.
Homologous embryonic structures reflect that the developmental programs of vertebrates are variations on a similar plan that existed in their last common ancestor. The small leg-like structures of some snakes species, like the Boa constrictorare vestigial structures. These remnant features serve no present purpose in snakes, but did serve a purpose in the snakes' tetrapod ancestor which walked on four limbs. Sometimes, organisms have structures that serve no apparent function but are homologous to useful structures in other organisms.
Examples of vestigial structures include the tailbone of humans a vestigial tailthe hind leg bones of whales, and the underdeveloped legs found in some snakes see picture at right 3 3. Analogous features To make things a little more interesting and complicated, not all physical features that look alike are marks of common ancestry. Instead, some physical similarities are analogous: This process is called convergent evolution. To converge means to come together, like two lines meeting at a point.
For example, two distantly related species that live in the Arctic, the arctic fox and the ptarmigan a birdboth undergo seasonal changes of color from dark to snowy white. Instead, this feature was favored separately in both species due to similar selective pressures.
Evidence for evolution
That is, the genetically determined ability to switch to light coloration in winter helped both foxes and ptarmigans survive and reproduce in a place with snowy winters and sharp-eyed predators. The Rhenanids became extinct over million years before the first stingrays evolved, yet they share quite a similar appearance.
Sandlance fish and chameleons have independent eye movements and focusing by use of the cornea. Cichlids of South America and the " sunfish " of North America are strikingly similar in morphology, ecology and behavior.
The two fishes are not related, yet are very similar. Peacock bass are native of South America and is a Cichla. While largemouth bass are native to Southern USA states and is a sunfish. The antifreeze protein of fish in the arctic and Antarcticcame about independently. In notothenioids, the AFGP gene arose from an ancestral trypsinogen-like serine protease gene. Stylophthalmine trait Sawfisha ray and unrelated Sawshark have sharp transverse teeth for hunting.
Some have active camouflage that changes with need. Prey are not sure which is the front, the direction of travel.Adaptive radiation class 12 for NEET - evolution biology lecture