Lecture 5 - Tetrapods and human evolution

What are tetrapods?

Tetrapods are vertebrates that have four limbs with five digits. They evolved from lobe-finned fish and moved from water to land.

Why did fish evolve legs and move to land?

Fish evolved legs to access empty niches, avoid competition, lay eggs in safer places, and escape predation in water.

What are chordates?

Chordates are animals with bilateral symmetry, a notochord, and true tissues (Eumetazoa). They are deuterostomes (the anus develops before the mouth).

What is the notochord in chordates?

The notochord is a rigid rod-like structure that may develop into a backbone, providing support for the body during development.

What are craniates?

Craniates are chordates with a head, such as hagfish, which are long and thin fish.

What are vertebrates?

Vertebrates are chordates with a head and a backbone. An example is the lamprey.

What are gnathostomes?

Gnathostomes are chordates, craniates, and vertebrates with jaws. They represent an important evolutionary development for vertebrates.

What are osteichthyans?

Osteichthyans are bony fish that have jaws, a head, and either lungs or swim bladders. This adaptation allows them to control buoyancy and move between water bodies.

What are lobe-fins?

Lobe-fins are a type of fin found in some chordates, craniates, vertebrates, gnathostomes, and osteichthyans. These fins have structures like the radius and ulna that are precursors to tetrapod limbs.

What is the significance of lobe-finned fish?

Lobe-finned fish are older than dinosaur fish and have fins with structures that resemble limbs, such as fin rays and bones like the radius and ulna.

What are the four groups of tetrapods today?

• Amphibians

• Reptiles

• Mammals

• Birds (which are closely related to reptiles, especially dinosaurs)

What are the requirements for surviving on land?

To survive on land, animals need skeletal support (for standing and movement), lungs for breathing air, limbs to move, and a neck to catch food.

What are the adaptations of lobe-finned fish for land survival?

Lobe-finned fish developed lungs, necks, and fins with digits that allowed them to survive in shallow water and potentially move onto land.

What is the significance of Tiktaalik in the evolution of tetrapods?

Tiktaalik is a transitional fossil, also called a "fishapod," that shows both fish and tetrapod traits. It had fins with digits and a head like a crocodile, bridging the gap between water and land animals.

What is Romer’s Gap?

Romer’s Gap is a period in the fossil record from 360 to 345 million years ago, during which early tetrapods evolved but left no direct fossil evidence.

What did early tetrapod limbs look like?

Early tetrapods had limbs with digits. Fish had similar structures, including a humorous, radius, and ulna, which evolved further in tetrapods to support movement on land.

How similar are humans to chimpanzees (Pan troglodytes)?

Humans are 99% similar to chimpanzees in terms of genetic makeup.

What are some key differences between humans and chimpanzees?

Differences include opposable thumbs (humans have thumbs, chimps have opposable toes), shorter hair in humans, and the ability for humans to speak due to a lower larynx and unattached hyoid bone.

What are the physical adaptations that make humans bipedal?

Humans have a foramen magnum beneath the skull for an upright head position, a lumbar curve in the spine for balance, inward-tilted pelvis blades, and feet adapted for weight-bearing rather than grasping.

How do human brains compare to chimpanzee brains?

Humans have larger brains than chimpanzees, though in terms of brain mass relative to body mass, humans do not have the largest brain. However, human brain size increased significantly over time as an adaptation to changing conditions.

How has cooking and food processing influenced human evolution?

Cooking made food easier to digest, reducing chewing time and allowing for the evolution of smaller guts and larger brains. This may have played a key role in human development.

What is an example of natural selection in humans?

Sickle cell resistance to malaria is an example. People with this genetic trait are less affected by malaria, providing a survival advantage.

What is lactose tolerance in humans?

Lactose tolerance refers to the ability of some adults to digest milk, a trait that provides an evolutionary advantage in populations where dairy is a significant nutrient source.