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Darwin's Theory (Natural Selection (Overproduction (Darwin knew that…
Darwin's Theory
Natural Selection
Overproduction
Darwin knew that some species produced far too many offspring that could survive. For example, many insects lay thousands of eggs yet he knew that not all of them could've survived because they would've been overpopulated
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Competition
Resources are limited, so Darwin knew that there must be competition to survive between species. For example, a penguin that could swim faster might escape a seal that another penguin might not. Then, the penguin would pass along the trait for speed and would help its offspring survive other seals.
Selection
Darwin saw that some variations in species made individuals more adapted towards their environment, being able to move faster to either escape predators or catch prey, thus being more likely to survive. If the organism had offspring, it might pass down those helpful traits. Darwin thought that over a long time, natural selection can lead to change. Helpful traits may gradually appear more frequently and the unhelpful ones might even disappear.
Environmental Change
A change in the environment can affect an organism's ability to survive. In some cases, a change in the environment can mean selection. Sometimes, only a small number of the species can survive the initial change, but once those few organisms reproduce enough, all of the offspring will have the trait.
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Galapagos Organisms
Darwin found many similarities between the animals on the Galapagos Islands and the animals on the mainland but he also found some differences which puzzled him. For example, iguanas on the islands had large claws that helped them grip slippery rocks while iguanas on the mainland had shorter claws.
Darwin also noticed differences between the same animals on different islands. For example, different finches on different islands had differently shaped beaks, made for different types of food consumpiton
Adaptions
There are two main types: one to help organisms eat, and one to help them from being eaten. For example, Darwin found that different finches had different shaped beaks depending on what they ate. Another adaption would be like a plant tasting bad so that it would be less appealing to eat. Another type of adaption is to help reproduce. Brightly colored flowers for insistence attract a variety of different insects to help spread pollen
Darwin's Observations
Diversity
Darwin was amazed by the diversity of life on planet Earth. Today there are more than 1.7 million species of organisms on Earth.
Fossils
Darwin found fossils of many animals and was puzzled about why they appeared different than the animals he saw living.
Darwin Himself
In December 1831, the Beagle, an English ship, set sail for a 5 year trip around the world. Darwin was aboard to study the natural world and observe living things that had never been seen before by an Englander.
Evolution
Darwin's Reasoning
Darwin reasoned that organisms that arrived on the Islands faced conditions that were different than those on the mainland and gradually changed over time to adapt to the different conditions
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