Darwin’s finches show variation in their __________.

Darwin’s theory is also known as:

Which of the following concepts is proposed by Charles Darwin?

Which of the following environmental factors affects the number of individuals in a population?

Adaptations are traits that _________________.

Natural selection:

Evolutions states that all organisms are evolved from a __________ ancestor.

The passing of genes to an organism that is not an offspring is called ___________.

Natural selection:

___________ is the driving force of evolution.    

• The changes can occur in many forms.
• With time small changes occur in the organism and these make them different than other animals of the same category. Thus variations occur. 
• Mutations are sudden changes that occur at the molecular level, it changes the genome of an organism.
• Sexual reproduction is also a source of change. As it also causes variations in offspring's. At the time of gamete formation some changes occurs due to recombination.
• So, among all the changes that occurs with time only those will develop that help the organism to remain alive.
• This is called natural selection.

Tortoises with dome-shaped shells have shorter necks because:

• Dome shaped tortoises are larger.
• These have shorter neck because these feed on the vegetation that is closer to the ground.
• So, they are able to eat with shorter neck.

Rheas are flightless birds found in ___________.

• Rheas are flightless birds that show similarities with ostrich.
• These belongs to the order Rheiformes.
• These are also called American ostrich because these are found only in South America.
• These have comparatively larger but nonfunctional wings.
• These are able to swim.

Charles Darwin was best known naturalist in the 19^th century for:

• Charles Darwin during his travel of Galapagos Island, noticed different organisms of different places of same geographic area.
• On the basis of his observations, he gave the theory of natural selection.
• According to the theory of natural selection, only those species can survive in the changing environment which develop such variations that helps them to remain alive. 
• This theory helped to understand the process of evolution properly.
• So, this was an acceptable idea for scientists.

The dome-shaped tortoise came from which islands?

• Dome shaped tortoises are found in Isabele Island.  
• These are found in moist areas and are adapted to feed on vegetation that is closer to the land.
• Darwin noticed some differences among tortoises that he found in Galapagos Island and other islands. These were different in size and shape.
• These differences of tortoises supported the theory of natural selection.

How many species of finches were observed by Darwin on the Galapagos?

• While traveling through the island, Darwin noticed some birds.
• These birds had different sizes and shapes of their beak.
• The structure of their beak was changed due to adaptations.
• All of these birds were evolved from same ancestors. Just their beak was different.
• The shape of their beak was changed according to their feeding habits.
• So, he observed 13 such finches.

______________ is a force that causes groups of organisms to change over time.

• A group of organism changes overtime because of variations.
• These variations are caused during sexual reproduction.
• Changes are also caused by mutations. These are sudden changes that are caused on genetic level. 
• So, all these changes caused in a group of organisms are developed in next generations only if these are helpful for them to survive in the changing environment.
• This is called adaptation. Only such changes are developed in generations of organism that helps them to evolve.
• So, nature selects only those who can survive better in the changing environment. This is called natural selection.
• This concept was given by scientist Charles Darwin. So, natural selection acts as a force that causes group of organisms to change overtime.