Changes Over Time
Define the following terms:
1. Evolution – the gradual change in species over time
2. Natural Selection – a process by which individuals that are better adapted to their environment are
more likely to survive and reproduce than others that are not
3. “Survival of the Fittest”– Organisms that are most fit with their environment will live longer and
reproduce, giving their good genes to their offspring.
4. Mutation – any change in the DNA of an organism.
5. Adaptation – behavior or physical characteristic that allows an organism to survive and reproduce in
its environment
6. Variation– any difference between organisms of the same species
7. Extinction– the disappearance of all members of a species from Earth
8. Diversity– the variety of organisms that inhabit the Earth
9. Fossil – the preserved remains or traces of an organism that lived in the past
10. Radioactive Dating – process where scientists look at the half-life of chemicals contained in rocks
around a fossil to determine the age of that fossil.
11. Homologous Structure- similar structures that related species have inherited from a common
ancestor (example – bones in bird’s wing, dolphin fin, and dog leg are very similar)
12. Missing Link- gaps in the fossil record.
1. A cheetah has a springy, flexible backbone that allows it to run faster than other big cats. Those
cheetahs with the most flexible backbones can run the fastest, helping them catch more food to care for
themselves and their young. This is an example of survival of the fittest.
2. In a population of salmon, a scientist notes that some fish have larger fins than others. These
differences among the traits of organisms in a population are known as variation
3. Fossils in the upper layer of the Earth resemble organisms from today while deeper fossils look like
organisms from the past.
4. Evolution depends on mutation because this is the way that new traits are created.
5. The wing of a bat, the flipper of a whale, and the arm of a human show that those three organisms
may have evolved from a common ancestor. These are known as homologous structures.
6. During “Who Wants to Live a Million Years” we found that our population increased its chance of
survival if we increased diversity
7. Most fossils are formed in sedimentary rock.
Answer the following questions in complete sentences:
8. Why did the population of peppered moths in England change from the light variation to the dark
variation after the Industrial Revolution? The white peppered moth was well camouflaged in the white
bark of the trees. When industry began, soot polluted the environment and covered the trees,
changing their color from white to black. The white moth was no longer camouflaged and the black
moth now blended in with the sooty trees. As a result, the white population began to get picked off
by birds and the black population became more plentiful as they were now better fit to their
surroundings.
9. Modern camels developed their traits of long eyelashes and fat-filled humps through natural
selection. What do you think occurs during the process of natural selection with relation to these traits?
Natural selection is the process of nature “choosing” which organisms live or die based on their
adaptations. Camels developed long eyelashes to block out the sun and prevent sand from entering
the eye. Fat filled humps keep them from starving while out in the barren desert. The camels that
developed these traits were best suited to live in their hot, dry environment will be “chosen” by
nature to live long enough to pass those good traits on to their offspring.
10. Darwin observed and recorded data about several different species of finches. According to Darwin,
how did the resources on each island affect the evolution of the finches?
Each island had unique food sources and the finches that came to that initially came to each island
and survived, had traits that fit with their environment. The longer the finch populations lived on the
island, the more reproduction took place, thus passing on good traits to the offspring and making
their beak shape more suited for the food source available.
11. Some scientists believe that giant woolly mammoths became extinct when the climate became
warmer. Why might this change have led to their extinction?
The woolly mammoth evolved to live in cold weather. When the climate changed, the mammoth’s
furry coat and thick layer of blubber no longer fit with the environment, causing their population to
decline and eventually die out.
12. In our bird beak lab, how did the different tools we used as bird beaks demonstrate adaptation?
Each beak was unique and was best suited for specific foods. The tweezers were best for picking up
small items like rice; the chopsticks were best for picking up larger items like rubber bands, etc. These
adaptations of being able to eat certain foods help the birds live in their environments successfully.
13. Think of an animal that lives in a swamp or marsh. What are three adaptations that this animal has
developed? Detail how each one helps it survive in this habitat.
Answers will vary Adaptation
Benefit
Webbed Feet
Aid in swimming
Fur or feathers that repel water
Keeps the animal warm and dry and able to fly (if
winged
Wide feet
Disperses body weight to keep from sinking in
muddy surface
14. In the phrase “survival of the fittest” what does it mean to be FIT?
Fitness refers to being healthy AND having traits that best fit with the environment. The fittest
organisms have the best adaptations and survive the longest, allowing them to mate and pass their
good traits on to their offspring.
15. Think of an animal that lives in the Sahara desert. What are three adaptations that this animal has
developed? Detail how each one helps it survive in this habitat.
Adaptation
Benefit
Nocturnal
Come out at night to avoid heat during the day
Dig den in the ground
Stay cool in your den during the day. Can also help
collect water vapor for drinking water
Large eyes
Help them to see at night
16. What is the importance of DNA in the human body? How does DNA relate to evolution?
DNA carries the instructions needed by the cell to make specific proteins which determine our traits.
When our DNA mutates, this accidental change may lead to a trait that produces a positive result,
negative result, or NO result. If positive, mutations can often lead to beneficial adaptations which
drive the process of evolution.
17. Think of an animal that lives in the snowy tundra. What are three adaptations that this animal has
developed? Detail how each one helps it survive in this habitat.
Adaptation
Benefit
Thick layer of blubber
Keep animal warm in the cold
Travel in tight herds or groups
Animals group together to keep heat in
Padded feet
Stalking prey silently
18. List and define the three types of camouflage and give an example of each.
Type of Camouflage
Example
Concealing Coloration- to blend in with environment
A polar bear in a snow drift
Disruptive coloration- to distract with contrasting
stripes and spots
Zebras traveling in a herd
Mimicry- to pretend to be something that they’re
not
A Walking stick on a branch or a viceroy butterfly
mimicking a monarch butterfly