Which of the following is an example of a vestigial organ that could be found in a transitional fossil?(1 point)

Question

Responses

an extra digit on both hands used for grasping
an extra digit on both hands used for grasping

an eye that is an organism's primary way to see
an eye that is an organism's primary way to see

a tail that is routinely used for balance
a tail that is routinely used for balance

a toe that does not contribute to movement

Tiktaalik was a prehistoric fish that was an ancestor to modern tetrapods. It shared anatomical features with tetrapods (e.g., four limbs) and fish (e.g., gills, scales). With these features, Tiktaalik could be best described as a(n)(1 point)
Responses

reptile.
reptile.

transitional form.
transitional form.

fossil.
fossil.

amphibian.

You and your friend inspect a group of fossils from different organisms with various features. Your friend is convinced that all of the fossils are unrelated, but you find evidence that these organisms share an ancestor. What is an example of evidence that you could use to best support this argument?(1 point)
Responses

heights
heights

number of bones
number of bones

tooth features
tooth features

patterns in limb structures

Which statement best describes why modern horses look the way they do?(1 point)
Responses

Aspects of horse anatomy evolved within a few generations to suit their environment.
Aspects of horse anatomy evolved within a few generations to suit their environment.

Aspects of horse anatomy evolved over hundreds of years to suit their environment.
Aspects of horse anatomy evolved over hundreds of years to suit their environment.

Aspects of horse anatomy evolved over millions of years to suit their environment.
Aspects of horse anatomy evolved over millions of years to suit their environment.

Aspects of horse anatomy evolved within a generation to suit their environment.

Key Words
evolves – changes over time
paleontologists – scientists who study fossils
ancestor – an early type of animal from which others have evolved
transitional fossil – a fossil that has features of both an ancestor organism and a more modern organism
Scientists try to figure out how an organism evolves or changes over time. They look at different kinds of evidence. One kind of evidence is how an animal’s body structures evolve over time. The horse’s foot is one such structure. Much of what we know about how the horse’s foot has changed over time is because of fossils.

Scientists called paleontologists study fossils. When they find a new fossil, they look to see where it might fit in with fossils they have already discovered. Scientists were able to put the fossils they found of horses in the past in the correct order based on the size and number of foot bones that were present. Look at the first animal in the picture. This animal is an ancestor of the horse. An ancestor is a much earlier animal from which others have evolved. This animal lived over 50 million years ago. Its body is very small, and its foot looked very different from that of the modern horse. Compare the foot bones beneath the first and last pictures. Notice that there are four bones (one large bone, and three smaller ones) in the ancestor, and only one large bone in the modern horse.

The three middle animals are also ancestors of the modern horse. They lived between 30 million years ago and two million years ago. The fossils of these horses are considered to be transitional fossils, since they have features of both the ancestor horse and the modern horse.

Compare the feet of the horse ancestors to the foot of the modern horse. Over millions of years, the small foot bones decreased both in size and number. Over the span of millions of years, the large foot bone got longer in order to support more of the horse’s weight. The first horse-like animal is an ancestor of the modern horse. All five of the horses in the diagram are related.

Scientists use many different kinds of evidence to get a more complete idea of how horses evolved. However, comparing fossils is a very important piece of the puzzle. Scientists study patterns in fossils to help determine how organisms evolved. What are these scientists called?

paleontologists

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Question 2

Describe why transitional fossils are useful in finding out how an organism evolved.

Possible response: Transitional fossils help scientists place organisms in the correct order because they have the features of both older and more modern organisms.

Answer 1

Let's break down the responses to each question you provided:

1. Which of the following is an example of a vestigial organ that could be found in a transitional fossil?

   • Correct Answer: a toe that does not contribute to movement.
   • Explanation: Vestigial organs are remnants of structures that served a purpose in an organism's ancestors but have lost or changed their original function over time.

2. Tiktaalik was a prehistoric fish that was an ancestor to modern tetrapods. It shared anatomical features with tetrapods (e.g., four limbs) and fish (e.g., gills, scales). With these features, Tiktaalik could be best described as a(n)

   • Correct Answer: transitional form.
   • Explanation: Tiktaalik is considered a transitional fossil because it displays characteristics of both fish and early tetrapods, showcasing evolutionary traits that link the two groups.

3. You and your friend inspect a group of fossils from different organisms with various features. Your friend is convinced that all of the fossils are unrelated, but you find evidence that these organisms share an ancestor. What is an example of evidence that you could use to best support this argument?

   • Correct Answer: patterns in limb structures.
   • Explanation: Similarities in the patterns of limb structures among different organisms can indicate a common ancestry, highlighting evolutionary relationships.

4. Which statement best describes why modern horses look the way they do?

   • Correct Answer: Aspects of horse anatomy evolved over millions of years to suit their environment.
   • Explanation: Evolution occurs over long time frames, and the anatomy of modern horses reflects adaptations to their environments accumulated over millions of years.

5. Describe why transitional fossils are useful in finding out how an organism evolved.

   • Possible response: Transitional fossils help scientists place organisms in the correct order because they have the features of both older and more modern organisms.
   • Explanation: This accurately captures the essence of transitional fossils, which serve as crucial evidence in understanding the evolutionary pathways and relationships among different species.

Feel free to ask if you have any further questions or need clarification on these responses!