EVOLUTION BY STAGE

EVOLUTIONBY

STAGES

WHAT IF COMPLICATED ORGANS, SUCH AS THE EYE , ARE SELECTED FOR THE ADVANTAGE THEY PROVIDE, HOW CAN THEY BE GENERATED BY A

SINGLE DNA CHANGE ?

SURELY SUCH COMPLEX ORGANS WILL BE CREATED BIT BY BIT OVER GENERATIONS?

BUT HOW CAN EACH INTERMEDIATE CHANGE BE SELECTED FOR?

THERE ARE A NUMBER OF POSSIBLE EXPLANATIONS

• EVEN AT AN INTERMEDIIATE STAGE , SUCH AS RUDIMENTARY EYE , CAN BE USEFUL TO SOME EXTENT. THIS MIGHT BE ENOUGH TO GIVE A FITNESS ADVANTAGE

•IN FACT , THE EYE LIKE THE WING - SEEMS TO BE A VERY POPULAR ADAPTATION.

•INSECTS HAVE THEM, SO DOES AN OCTOPUS AND SO DO THE VERTEBRATES.

•AND THE STRUCTURE OF THE EYE IN EACH OF THESE ORGANISMS ARE DIFFERENT – ENOUGH FOR THEM TO HAVE SEPARATE EVOLUTIONARY ORIGINS.

A CHANGE THAT IS USEFUL FOR ONE PROPERTY TO START BECOME USEFUL LATER FOR QUITE A

DIFFERENT FUNCTION.

FEATHERS FOR EXAMPLE CAN START

OUT AS PROTECTION INCOLD WEATHER

BUT LATER, THEY MIGHT BECOME

USEFUL FOR FLIGHT

IN FACT SOME DINOSAURS

HAD FEATHERS ALTHOUGH

THEY COULD NOT FLY WITH

IT.

BUT BIRDS SEEM TO HAVE ADAPTED THE FEATHERS TO

FLIGHT.

THIS, OF COURSE MEANS THATBIRDS ARE VERY CLOSELY

RELATED TO REPTILES, SINCE DINOSAURS WERE REPTILES

EVOLUTION OF BIRDSFROM DINOSAURS

•Some dissimilar looking structure also evolved from common ancestor.•Example : wild cabbage plant

•Humans have cultivated wild cabbage as a food plant and generated different vegetables from it by selection, mainly by artificial selection.

What are some of reason why artificial methods have been taken for wild cabbage?????

Some farmers wanted to select for very short distance between leaves and have bred the cabbage they eat

Some wanted to select for arrested flower development and have bred broccoli, and have made cauliflower

Some have selected for swollen parts and come up with kohlrabi

Some have simply

looked for slightly large leaves and have come

up with leafy vegetable

called kale.

It is the evolutionary history of an organism or

group of related

organism

Phylogeny

It is any change in the structure Or functioning of an organism That makes its better suited to

its environment

Adaptation

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The beaver has many interesting adaptations.

They have long, sharp incisors that never stop growing, so as they wear them down chewing trees, they keep growing back.

They can also close their nostrils and throat while carrying sticks around in the water. This keeps them from drowning while they carry sticks to and fro underwater.

.

They also have a thick coat so they can swim under the ice in the winter and oil glands to keep their fur well oiled. The beaver is well adapted to its habitat

They have a thin membrane over their eyes that allows them to see underwater while protecting their eyes like swim goggles!

It is the idea that organism those are more distantly related will accumulate a

greater number of difference in their DNA. Such studies traces the

evolutionary relationship.

Molecular phylogeny