Life on Earth is always changing. ____, like eye color or fur pattern, are passed from parents to their ____ through units of information called ____. In ____ reproduction, two parents combine their genes to create offspring, leading to lots of ____, or differences, between individuals. In ____ reproduction, one parent makes an exact ____ of itself, so there is very ____ variation. Sometimes, ____ mutations occur. A mutation is a change in the ____ code. Mutations can be ____, harmful, or have no effect at all, and they are an important way new traits appear in living things. One way that species ____ over time is through ____. In natural selection, genetic ____ that are beneficial to an individual's survival are passed on through ____. Because they have more ____, the helpful traits become more ____ in the population. For example, dark-colored mice on dark ____ survive longer than light-colored ones because they are harder for ____ to see. Over time, more and more mice in that ____ are ____-colored. A core part of the concept of natural ____ is that the environment "____" for certain traits, leading to the ____ of populations over time. When a helpful trait becomes common, it is called an ____. An adaptation is any trait that ____ an organism's chances of ____ and reproduction. The better adapted an organism is, the higher its ____. In science, fitness means how good an organism is at surviving in its ____ and ____ offspring. Organisms with higher fitness are more likely to pass on their traits to the next generation. Over many generations, adaptations can completely change the way a species looks, acts, or lives. This process is known as evolution Scientists have many ways to find evidence that species have evolved over time. ____, which are preserved remains or traces of ancient ____, show us what species looked like ____ of years ago. ____, the study of how animals develop before they are born, shows that many animals look very similar as ____, suggesting they share a ____. Homologous ____, like a human arm, a bat wing, and a whale flipper, have the same basic ____ but are used for different ____. ____ structures, like the wings of birds and insects, perform the same job (flying) but are built very ____, meaning they ____ separately. Sometimes, species cannot ____ quickly enough to changes in their ____ and go through ____. Extinction happens when every member of a species dies out and the species no longer exists. Causes of extinction include sudden environmental ____, stronger ____ from other species, or the spread of new ____. Although the species disappears, ____ can tell us their story and help scientists understand the history of ____ on Earth. In addition to natural selection, humans can also influence traits in living things through ____. Artificial selection happens when ____ choose ____ they want in plants or animals and ____ individuals that have those traits. ____ is a type of artificial selection where humans pick two parents with the ____ traits, like the fastest horses or the sweetest strawberries, to produce offspring with those traits. Over time, selective breeding can create plants and animals that are very ____ from their wild ancestors. Today, scientists can also change traits more directly using ____. Genetic modification (____) involves changing an organism’s ____ in a ____ to give it new traits. For example, scientists can create crops that resist pests or grow faster by ____ specific ____. Genetic modification allows changes to happen much ____ than natural selection or selective breeding. Both ____ selection and genetic ____ show how humans can guide the way living things ____, just like nature does through ____ selection — but in these cases, ____ are making the choices instead of the ____.

Notes #4 Natural Selection & Evolution

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