Chapter Seven: The Evolution of Living Things
Section One: Change Over Time
Adaptation- a characteristic that improves an individual's ability to survive and reproduce in a particular environment
Species- a group of organisms that are closely related and can mate to produce fertile offspring
Evolution- the process in which inherited characteristics within a population change over generations such that new species sometimes arise
Fossil- the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
Fossil record- a historical sequence of life indicated by fossils found in layers of the Earth's crust
Chapter Seven, Section One: Summary
The structure of humans, cats, whales, and bats are similar.
Section one was about evolution and adaptation. Groups of individuals apart of a same species is a population.Scientists think when populations change, new species are formed. Layers in the Earths crust are made of sediment that are carried by wind or water and deposited neatly. Older layers are deposited before newer layers. Fossils can be whole organisms, part of the organism, or their footprints. Fossils form when sediment covers a dead organism. The minerals that are in the sediment gradually turn the organism into stone. Not everything that dies turns into a fossil. Certain conditions have to be right for it to turn into a fossil. Scientists have made a timeline of life called the fossil record. it estimates the age and appearance of fossils. Fossils found in newer layers are more like present day organisms. Fossils in older layers are less similar to organisms today. Older fossils of older life may not exist anymore. Scientists think all living organisms came from common ancestors. Scientists think whales came from ancestors that had four legs. Whales have tiny hip bones which they inherited from their ancestors. A human arm, a cat leg, the flipper of a dolphin, and a bat wing are similar because the bones are similar in the structure. Scientists compare DNA in organisms. The more similar the DNA sequence is in an organisms, the more related they are.
Section Two: How Does Evolution Happen?
Trait- a genetically determined characteristic
Selective Breeding- the human practice of breeding animals or plants that have certain desired traits
Natural Selection- the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do; a theory to explain the mechanism of evoulution
Chapter Seven, Section Two: Summary
Different beaks of Galapagos finches.
Section two was about Charles Darwin. He was a naturalist on the Beagle, a British ship. He made it to the Galapagos Islands of the coast of Ecuador. He noticed the plants and animals were similar to the ones on Ecuador. The finches on the island had adapted beaks for eating. After Darwin returned he wanted to know why the animals were alike but so different in their adaptation. He hypothesized the finches were blown from South America and adapted to the islands. Farmers selectively bred organisms with traits they liked. Thomas Malthus wrote a book saying if the population keeps going up there won't be enough food. The organisms can die of disease, predation, starvation, and competition. Charles Lyell wrote a book saying Earth was formed over a longer process than other people thought. Darwin's theory of natural selection was overpopulation, inherited variation, struggle to survive, and successful reproduction. Darwin knew that organisms inherit traits but he did not know how. Traits that help an organism survive to reproduce are passed to the offspring.
Section Three: Natural Selection in Action
Generation Time- the period between the birth of one generation and the birth of the next generation
Speciation- the formation of new species as a result of evolution
Chapter Seven, Section Three: Summary
Speciation of the Galapagos finches.
Section three was about natural selection in nature. Some organisms adapt to hunting. Male elephants in Africa were being hunted for their tusks. Before only one percent of elephants were born tusk less. Today it is up to fifteen percent of elephants born tusk less. Some insects can adapt to insecticides. Then they pass the resistant trait to the offspring. Insects evolve quickly because they have a short generation. Competition for mates can also select for an adaptation. Male birds that are colorful will get mates. They can pass on their traits to their offspring. Non-colorful mates won't get many mates causing them not to be able to pass on their traits. New species form when a population gets separated adapting to the new environment, and no longer being able to reproduce with the other population.
Now that you know about evolution, here is a song about it.