UNIT 7 ck12’s 5.24-5.25

Question 1

What is gradualism in the context of evolution?

Answer 1

Gradualism is a model of the timing of evolution where changes occur gradually during stable geologic and climatic conditions.

This concept was originally proposed by Darwin.

Question 2

What is punctuated equilibrium?

Answer 2

Punctuated equilibrium is a model of evolution that suggests long periods of little change are interrupted by bursts of rapid change, especially during changing geologic and climatic conditions.

This model is better supported by the fossil record than gradualism.

Question 3

How do geologic and climatic conditions affect the rate of evolution?

Answer 3

Stable conditions allow for gradual evolution, while changing conditions can lead to rapid evolutionary changes.

This indicates that evolution is not a uniform process.

Question 4

True or False: Gradualism is better supported by the fossil record than punctuated equilibrium.

Answer 4

False

Punctuated equilibrium is better supported by the fossil record.

Question 5

Fill in the blank: The model of evolution that describes rapid changes during periods of environmental upheaval is called _______.

Answer 5

punctuated equilibrium

Question 6

What does the fossil record suggest about the timing of evolution?

Answer 6

The fossil record suggests that punctuated equilibrium is a more accurate model than gradualism.

This indicates that evolution can occur in bursts rather than steadily.

Question 7

What happens to niches during sudden geologic and climatic changes?

Answer 7

Niches left open by sudden changes may be rapidly filled by bursts of evolution.

This highlights the relationship between environmental changes and evolutionary responses.

Question 8

Who were the ancestors of the earliest animals?

Answer 8

Marine protists that lived in colonies

Question 9

What is the process that led to the evolution of the first multicellular animal?

Answer 9

Cells of some protist colonies became specialized for different jobs and needed each other for survival

Question 10

What type of sponge cell is mentioned in relation to protist cells?

Answer 10

Choanocyte

Question 11

How does the choanocyte support the hypothesis that animals evolved from protists?

Answer 11

It looks a lot like the protist cell

Question 12

Fill in the blank: The first multicellular animal evolved from specialized cells of _______.

Answer 12

[protist colonies]

Question 13

True or False: The earliest animals may have evolved from land-based organisms.

Answer 13

False

Question 14

What are some important adaptations that evolved in invertebrates?

Answer 14

• Tissues, organs, and organ systems
• A symmetrical body
• A brain and sensory organs
• A fluid-filled body cavity
• A complete digestive system
• A body divided into segments

These adaptations were crucial for the evolution of vertebrates.

Question 15

Who were the first animals to colonize land?

Answer 15

Invertebrates, most likely arthropods

While amphibians are often thought of as the first vertebrates on land, invertebrates were the pioneers.

Question 16

What adaptations were necessary for animals moving from water to land?

Answer 16

• A way to keep their body from drying out
• Support for their body on dry land
• Ability to breathe oxygen without gills

These adaptations were essential for survival in a terrestrial environment.

Question 17

What is an exoskeleton?

Answer 17

A non-bony skeleton that forms on the outside of the body

Early arthropods evolved exoskeletons to support their bodies and retain water.

Question 18

Fill in the blank: The move to land required new adaptations, including a way to keep the body from _______.

Answer 18

drying out

Question 19

True or False: Amphibians were the first animals to colonize land.

Answer 19

False

Question 20

What body feature helps invertebrates retain water when moving to land?

Answer 20

Exoskeleton

The exoskeleton acts as a protective barrier against desiccation.

Question 21

List some key features of invertebrates that contributed to the evolution of vertebrates.

Answer 21

• Tissues, organs, and organ systems
• Symmetrical body
• Brain and sensory organs
• Fluid-filled body cavity
• Complete digestive system
• Segmented body

These features allowed for more complex life forms to evolve.

Question 22

What is a notochord?

Answer 22

A rigid rod that runs the length of the body, supports the body, and gives it shape.

Question 23

What are animals with a notochord called?

Answer 23

Chordates.

Question 24

What is one function of the notochord?

Answer 24

It provides a place for muscles to anchor and counterbalances them when they contract.

Question 25

What is a hollow nerve cord?

Answer 25

A structure that runs along the top of the body in chordates.

Question 26

Name two other features of chordates.

Answer 26

Gill slits and a tail.

Question 27

True or False: Many modern chordates have some chordate features only as embryos.

Answer 27

True.

Question 28

Fill in the blank: Animals with a notochord are called _______.

Answer 28

[chordates].

Question 29

From what did vertebrates evolve?

Answer 29

Primitive chordates

Question 30

Approximately how many years ago did vertebrates evolve?

Answer 30

About 550 million years ago

Question 31

What are the earliest vertebrates believed to be?

Answer 31

Jawless fish, like the hagfish

Question 32

What structure did vertebrates evolve to replace the notochord?

Answer 32

A backbone

Question 33

What is the function of the cranium in vertebrates?

Answer 33

To enclose and protect the brain

Question 34

Fill in the blank: Vertebrates evolved a _______ to replace the notochord.

Answer 34

backbone

Question 35

True or False: Vertebrates evolved a cranium after the embryo stage.

Answer 35

True

Question 36

What were the first animals to have true lungs and limbs for life on land?

Answer 36

Amphibians ## Footnote Amphibians still needed to return to water to reproduce.

Question 37

What is a key reason amphibians had to return to water for reproduction?

Answer 37

Their eggs lacked a waterproof covering ## Footnote This caused the eggs to dry out on land.

Question 38

What are amniotes?

Answer 38

Animals that produce eggs with internal membranes ## Footnote These membranes allow gases but not water to pass through.

Question 39

What is the significance of the amniotic egg?

Answer 39

It allows an embryo to breathe without drying out ## Footnote Amniotic eggs were the first eggs that could be laid on land.

Question 40

When did the earliest amniotes evolve?

Answer 40

About 350 million years ago ## Footnote This marks a significant point in vertebrate evolution.

Question 41

What are the two important groups that evolved from early amniotes?

Answer 41

Synapsids and sauropsids ## Footnote These groups evolved into mammals and reptiles, respectively.

Question 42

What did synapsids evolve into?

Answer 42

Mammals ## Footnote This group is crucial for the evolution of warm-blooded vertebrates.

Question 43

What did sauropsids give rise to?

Answer 43

Reptiles, dinosaurs, and birds ## Footnote This group includes a diverse range of species.