When people think of evolution they think of a simple creature becoming more complex one, which to a degree is correct but is not always true, evolution works in necessity.
For example take the Kakapo a flightless parrot from New Zealand, their ancestors could fly but because at the time there where no predators on the island (cats and dogs have gotten to the island but the New Zealand government is taking steps to protect the Kakapo). They lost the ability to fly as they had no need to escape predators.
Another example is the Olm a cave Salamander, because they live in complete darkness they have no need for sight so over time their eyes became under developed and have left them blind.
The loss of flight and sight might seem like a step backwards but because they no longer needed these abilities so evolution got rid of them.
There are several types of evolution.
Convergent Evolution.
Is when animals that don't have a common ancestor to each other but evolve to behave or have similar attributes to each other such as ants and termites. Ants are in the Hymenoptera order so they
are related to Bees and Wasps and Termites are in the Blattodea order they are distantly related to Cockroaches.
Even though they are not related they both live in colonies with individuals doing a set jobs, they are both ruled by a queen that is the mothers to all the individuals in the colony, they create their own nests or mounds but Termites tend to make more advanced mounds Ants (Convergent evolution) compared to Ants such as the Wood ants.
Divergent evolution
Is when when animals are related but do not look as though they are an example would be the Hyrax, Hyraxes are related to the Elephant. Even though the Hyrax looks like a rodents and are found in trees and scurrying between rocks and the Elephant is the largest land mammal they are both related even though they couldn't look more different.
Dimorphic Evolution
Is when the males and females look different in some cases the males and females can look like they are from 2 different species a good example of this is the Elephant seal the males can be more than 4 times the size of the females.
Bottleneck evolution
Normally happens after a mass event that kills a large number of a species population. This happened to Cheetahs about 10,000 years ago when they almost became extinct. So many cheetahs died that their genetic variations have shrunk to such an extent that their evolution has almost came to a stop. Genetic variations are important for animals to change, adapt and evolve. Favourable genetic variations are passed onto the next generation, they control everything from the colour of your eyes to your ability to deal with infection.
Parrallel evolution
Is when species that have a common ancestor but live in different parts of a country or a different country entirely. these different species evolve to look like the same species due to similar environmental pressures. The Indian crested porcupine and the Cape porcupine would be an example of this.
Coevolution evolution
Is when 2 species evolve a competitive relationship or mutual relationship with each other. A competitive relationship is when a Parasitic wasps will paralyse a caterpillar and lay its eggs in it so their young will have food for when they hatch. An example of a mutual relationship is between the Hummingbird and plants as the Hummingbird gets food and the plant gets to distribute its pollen.
Adaptive radiation
This happens when an animal comes to a new habitat such as an island, a good example is the Galapagos finches. once their ancestor reached the Galapagos the finch evolved to fill in all the different niches.
The Small ground finch which feed on insects on iguanas and tortoises, the Cactus ground finch feeds on the flowers of the Opuntia Finches (Adaptive radiation) cactus and the Woodpecker finch uses spines of the cactus to pierce beetle grubs hidden in rotten wood.
Speciation
This is the blue print of evolution with one organism evolving into 1 or 2 other species, so every species at one point or another would have evolved due to speciation at some point during its evolutionary history. Humans and Chimps would be an example of speciation as we both share a
common ancestor.
Chimp (Speciation)
Despeciation
This is when an organism evolves into 2 different species and then thous species hybridise and are replaces by 1 species. An example of this is the Common raven in North America, it was believed their was just the 1 species the common raven but later found to be 2 species that separated at some point in the past the Holarctic and California Raven. These 2 species are now hybridising and in Raven (Despeciation) these areas the Holarctic and Californian Mobbing a Golden eagle Raven are being replaced by these hybrids being referred to as the Common raven.
Iterative evolution
This is also known as repeated evolution. The best example would be the Aldabra rail which is a flightless bird on Aldabra Island they evolved from the white throated rail that is still found in Madagascar. Because of predator the white throated rail still flys and some flew over to Aldabra Island and because of a lack predator these birds lost the ability to fly as they have no use for it. Studys have shown this is not the first time Aldabra rail evolved they went extinct in the past and have repeated due to Iterative evolution it evolved once again from the white throated rail.
Thanks for reading.