Natural Selection Reading

Natural Selection Readings

The process of natural selection has to do with traits, random mutation, limiting factors, and populations. A characteristic that an organism has is referred to as a trait, i.e. a bunny having a long tail or short tail. Variations of traits in animals or plants arise from mutations, which cannot be controlled by that organism. Random mutations are spontaneous changes within an organism’s DNA. The environment determines if certain traits will help an organism adapt. Adaptations that help an organism to better survive and reproduce are called positive mutations. Certain traits that decrease or diminish an organism’s survival or reproduction are called negative mutations. Neutral mutations are traits that have neither a positive or negative effect on an organism’s adaptability. Limiting factors prevent a population from growing any larger due to the fact that death occurs in organisms before they are able to reproduce. A population is defined as all of the same species in a specific environment. 

Concept of natural selection:

The natural environment affects the certain traits that help an organism survive. The organism with the best traits for survival is selected for, so we call this process “selection” or “survival of the fittest.”  The organism with the “fittest” traits for its environment will not be selected against, and will then have a higher chance of passing on those traits. One example would be a bunny with a random genetic mutation that ends up with longer teeth.  If having longer teeth helped the bunny to find food more easily, or if it could eat more types of food than the other bunnies, than this bunny would have a higher chance of survival because it has more food options. All the other bunnies with short teeth would not be able to eat things that require long teeth. The bunnies with short teeth would then have a harder time surviving because they have less food options. What if that type of food runs out? What will the bunnies with short teeth eat? The bunnies with the adaptation of longer teeth have an advantage of surviving over the bunnies with shorter teeth. In this example, food is the limiting factor.

Over time, with changes in the environment, either both bunnies will survive and eventually create new species, or one type of bunny will undergo natural selection and no longer be able to survive without the best adaptation. In contrast, other bunnies with short teeth would have a harder time getting food; this would lead them to slowly die out. Then, over a long period of time, within a same or similar environment, through successive generations of reproduction and passing on long teeth trait to offspring, the longer-toothed bunnies would thrive. This results in an evolution of bunny from short teeth to longer teeth.

Different factors in an environment work together with each other in various ways. These different factors consist of biotic factors or living components and abiotic factors, or nonliving things. For example, a biotic factor in the previous bunny scenario would be the food.

Natural selection and evolution

Scientists have found evidence that trace the simplest living creatures on earth back to 400 million years ago. Today, we have many different varieties of complex organism that are both single cellular and multicellular. The mystery behind these transformations has puzzled scientist and researchers for centuries.

In the 19^th century, a great naturalist named Charles Darwin made great discoveries through his detailed field observations with finches in the Galapagos Islands. Darwin’s findings convinced him that species gradually changed after each generation, in other words they evolved. The idea of evolution had been around long before Darwin but he was the first to find enough evidence able to prove the idea. Fossils also provided another key to evolution by showing relationships between prehistoric animals and today’s animals. Other fossil records made it possible to show how an individual organism could evolve into another and then be linked to today’s organisms. After proving that evolution was possible, the question of how it happened still remained. Darwin used a mix of his own ideas and others to propose that evolution took place by 'natural selection'. Therefore, it is important to understand that natural selection is a process that leads to evolution.

 

LT: I can explain how Natural Selection relates to inherited and acquired traits.

  Instructions:

1. Read the Natural Selection reading

2. For EACH paragraph

            *Write down the main idea

            *Summarize the paragraph

            *Draw an illustration of the paragraph

Vocabulary Sheet 

Paragraph Main Idea	Summarize	Illustration
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LT: I can explain how Natural Selection relates to inherited and acquired traits.

Name: ___________________ Date: ______________ Class Period: _____________

Vocabulary Words

Word	Definition	Examples from Reading	Picture
Trait (rasgo)
Adaptation (adaptacion)
Inherited trait (Rasgo heredado)
Mutation (Mutacion)
Limiting Factors (Factor Limitante)
Population (Población)
Natural Selection (La Selección natural)
Adaptive Radiation (Adaptación de radiación)
Biotic (Bióticos)
Abiotic (Abiótico)