Evolution 2

Describe a human foot

no divergent toe. rigid, for balance

Describe the chimp ilium and Ischium

ilium- Narrow/long and flat Ischium- Tall/longer

Describe human pelvis

ilium- Wide horizontally, rounded ischium-Short

Describe Ardi's Pelvis, ilium and ischium

ilium- Wider horizontally, more rounded like a humans ischium- Tall and long like a chimps

Tetrapods first appear in the fossil record _______ million years ago.

365

Which lobe-finned fish is alive today?

Coelacanth

Identify at least two sources of data that scientists can compare to determine the evolutionary relationships between two or more species.

DNA, Anatomy, and physiology.

Charles Darwin proposed that modern humans directly descended from chimpanzees. Support or refute this statement with evidence from the video clip.

Darwin did not support the belief that humans evolved from chimpanzees. He appreciated common ancestry and the belief that both humans and chimpanzees evolved from a common ancestor but diverged into two separate lines.

Australopithecus is an early hominid that is now extinct. Why does Dr. White contend that Australopithecus is not completely gone?

Dr. White contends that Australopithecus is not completely gone because genetic material is still present in all of us humans today.

Are humans more closely related to gorillas or orangutans? State the evidence.

Humans are more closely related to gorillas than to orangutans. Our genes (and our genome as a whole) are more similar to those of gorillas, indicating that we are more closely related to gorillas. This can be shown on a phylogenetic tree.

Examples of tetrapods include _____________ _________ ___________ and _________.

Mammals, Birds, reptiles, and amphibians.

________________ and _________________ are fossil species that have characteristics unique to fish as well as characteristics found in fish and tetrapods. Describe the characteristics of lobe-finned fish that are similar to those of tetrapods.

Panderichthys and Eusthenopteron Pairs of fins are supported by a single bone that is equivalent to a modern tetrapods humerus and femur. Digit like bones in front of fins. eyes on top of head (early tetrapod adaptation)

What is a phylogenetic tree used to illustrate?

Phylogenetic trees are used to illustrate the evolutionary relationships between organisms.

What is homology? To what are fins homologous?

Shared ancestry between similar features is called homology. Fish, for example, have fins that are homologous to the limbs of tetrapods. The bones and their structure are features that are related to common ancestry and are therefore homologous.

Why is Tiktaalik such an important transitional fossil?

The presence of tiktaalik helps to bridge the gap between the fish like tetrapods and the tetrapod like fish, because of its characteristics. Tiktaalik features include, Limb like fins with a wrist, a fused pelvic girdle that suggests significant weight bearing out of the water, it had a flat head with eyes on top suggestive of shallow water habitat or land dwelling. Tiktaalik also possesses a large ribcage for lung breathing and lung support while on land, as well as a separated head and neck region.

Tetrapods are _________________________.

four limbed animals with two pairs of limbs.

Fish use ____________to breathe underwater. (However, many species of lobe-finned fishes that evolved during the Devonian period also had _____________.

gills, lungs

Lungs allow an animal to breathe _______. Why did this adaptation evolve?

air. Low levels of oxygen in the water.

Why is a sturdy ribcage important for tetrapods?

supports the weight of the body out of water and keeps the lungs from collapsing.

Charles Darwin predicted that tetrapods evolved from _______. What observation leads to that hypothesis? (Name 3 reasons)

Fish. Fish fossils found over 500 MYA Fossils predate tetrapod fossils. Fish have a backbone and a spinal cord.

Based on your answer above, is Ardi the common ancestor of humans and chimpanzees? State the evidence.

The evidence of Ardi's bipedalism helps to identify Ardi as a common ancestor to humans. So no, Ardi is not the common ancestor of humans and chimps. In essence, both humans and chimps have evolved distinctly and separately although they share a common ancestor.

Why did the excavation site for Ardi need to remain wet?

To help avoid expansion and contraction of the clay around the bones. If the clay was allowed to expand and contract it could destroy the bones underneath.

Once the finger bones of Ardi were discovered, why did the crew begin to excavate and sieve the surrounding area?

To try and locate more of the skeleton.

Many transitional species had gills which means that they lived in _____________________.

aquatic environments.

Most modern tetrapods have _________digits on front limbs and ________digits on back limbs, although some species have fewer. How does this number compare to the number of digits on the limbs of transitional fossil forms?

five, five. Pederpes: 6 front and 5 back Tulerpeton: 6 digits front and back Ichthyostega: 7 digits front and back Acanthostega: 8 digits front and back

Bones are one anatomical feature that can provide a wealth of information. List seven things scientists can learn about an organism by examining its bones.

1)Size 2)shape 3)Composition determines age 4)Position- prey or predator 5)Teeth- diet or social behavior 6)Pelvis size and shape- reproduction 7)Pelvis and spine- walks upright or on all fours

What is a hominid (or hominin)?

A hominid is a primate that diverged into the human branch of the tree of life. Traits including bipedalism share more commonalities to humans than to chimpanzees.

_______________________ and ____________________ have been called fish-like tetrapods. Explain why they are described as such and describe the environment in which they probably lived.

Acanthostega and Icythyostega -Icythyostega has both the characteristics of a fish and a tetrapod, it has a fishlike tail, gills, an amphibian like head and four limbs with seven digits. Icythyostega also had a sturdy rib cage, a feature of the modern tetrapod, but it was likely only on land for short periods due to its lack of limb strength. -Acanthostega possessed four limbs with limited motion elbow joints, a short ribcage not ideal for terrestrial locomotion, and a set of gills promoting its aquatic lifestyle.

Where does Ardi belong in the tree of life? State the evidence.

Ardi belongs on the more human side of the tree of life. This is evident due to Ardi's evolutionary developments being more closely related to humans, especially bipedalism. Thus, Ardi is a hominid.

Conclusions from feet comparisons

Ardi foot is like a chimp and a human Ardi had better balance bipedally than a chimp but better grasping ability than a human when climbing trees.

Conclusions from teeth comparisons

Ardi males were probably less competitive than chimp males

Conclusions from pelvis comparisons

Ardi pelvis is like both chimp and human, so Ardi probably walked bipedally and climbed trees.

Describe the Teeth of chimpanzee

Canines are Sharp and large in male. Smaller in female but still large and sharp.

Describe human canines

Canines are small, not sharp, and comparable across both sexes. Like Ardi.

Describe ardi's teeth

Canines differ less between sexes, are blunter, and less prominent.

Describe the chimp foot

Divergent toe and longer digits for grasping

Desrcibe Ardi's foot

Divergent toe, but more rigid rest of foot

How did the anatomy of the shoulder and head change during tetrapod evolution?

During evolution the shoulder and head bones became separated from each other, allowing for more independent movement from the body.

What evidence would you expect to find to support Darwin's hypothesis that tetrapods evolved from fish? What age rocks would you look in and why?

Evidence would be: Transitional fossils with features of both fish and tetrapods. Transitional fossils will likely date back between 380-360 million years ago. This is because tetrapods are after this period and fish are before this period, therefore any evidence of transitional fossils must be between the two periods.

Based on genetic evidence, humans are most closely related to which two species?

Humans are most closely related to the Chimpanzee and Bonobo.

Why do many of the transitional fossils between fish and tetrapods have flat heads?

It was likely an adaptation to living in shallow waters.

Why are lobe-finned fish thought to be the closest relatives to tetrapods?

Lobe finned fish have similar bones at the base of their fins that are like the femur and humerus of tetrapods.

Tetrapods use _________ to breathe. Do any modern tetrapods have gills? Explain.

Lungs, Some amphibians have gills as larva, but most lose their gills into adulthood. This adaptation was for life on land.

____________________ and ______________are early tetrapods that do not have features unique to fish. Describe how these two species differ anatomically and what that means about where they each lived.

Pederpes and Tulerpeton The main anatomical difference between the two fossils is the shape of the head. Tulerpeton presents a flat head adaptive for living in shallow water, although it is likely that Tulerpeton spent more time on land than in water. Pederpes however, presents a head that is not flat, suggesting that Pederpes was exclusively terrestrial. Additionally, while Tulerpeton possessed 6 digits on each limb, pederpes only had 6 digits on the front two limbs, and 5 on the back two limbs.

In fossils, what anatomical evidence indicates that gills were present?

The shoulder bones and skulls of fossils can show the presence of tiny bony structures that supported gills.

What was the point of marking the excavation site with small yellow flags?

This helped to identify where each bone was found.