Question 1

Evolutionary trees are continually revised by scientists as new information becomes available from various sources such as

Accepted Answer

A) better understanding of the details of physiological processes. 
B) additional,similar fossils found in relation to the geological time period. 
C) the continued evolution of current Earth species. 
D) the identification of alien species that have reached Earth via meteorites and comets. 
A) better understanding of the details of physiological processes. 
B) additional,similar fossils found in relation to the geological time period. 
C) the continued evolution of current Earth species. 
D) the identification of alien species that have reached Earth via meteorites and comets.

Question 2

Although it is costly to produce fruit,the large number of fruit-producing plant species attests to its success as an evolutionary adaptation.In what way is fruit production helpful to plants?

Accepted Answer

A) Fruits attract pollinators like insects and birds to move pollen between different plants. 
B) Fruit toxins can discourage potential consumers from eating the plant. 
C) Plants can store energy in fruits during summer and then later recover the energy during winter,when the fruit decomposes. 
D) Consumers eating fruits also eat seeds that,when not digested,can be deposited far from the parent plant and increase the range of that plant species. 
A) Fruits attract pollinators like insects and birds to move pollen between different plants. 
B) Fruit toxins can discourage potential consumers from eating the plant. 
C) Plants can store energy in fruits during summer and then later recover the energy during winter,when the fruit decomposes. 
D) Consumers eating fruits also eat seeds that,when not digested,can be deposited far from the parent plant and increase the range of that plant species.

Question 3

Identify key characteristics for kingdom Fungi and provide three examples of members of this kingdom.

Accepted Answer

Fungi are eukaryotes.Some fungi are sing

Question 4

Gymnosperms and angiosperms are believed to be more closely related to one another than the other major plant groups because

Accepted Answer

A) they alone possess vascular systems. 
B) both groups produce separate male and female gametes. 
C) they provide their embryos with stored food that can support growth before photosynthesis begins. 
D) both groups protect their seeds within protective structures. 
A) they alone possess vascular systems. 
B) both groups produce separate male and female gametes. 
C) they provide their embryos with stored food that can support growth before photosynthesis begins. 
D) both groups protect their seeds within protective structures.

Question 5

The fourth mass extinction occurred about 200 mya at the end of the ________ period.This extinction eliminated 35 percent of the existing animal species including ________.

Accepted Answer

A) Triassic;reptiles,early dinosaurs,and the first mammals 
B) Jurassic;dinosaurs,first birds,and many flowering plants 
C) Silurian;insects,birds,and mammals 
D) Carboniferous;insects,birds,and mammals 
A) Triassic;reptiles,early dinosaurs,and the first mammals 
B) Jurassic;dinosaurs,first birds,and many flowering plants 
C) Silurian;insects,birds,and mammals 
D) Carboniferous;insects,birds,and mammals

Question 6

Resolving the relationship between the various kingdoms has been challenging because species often resemble one another.For example,the kingdom ________ contains some organisms that are animal-like and others that are plantlike.

Accepted Answer

A) Bacteria 
B) Fungi 
C) Archaea 
D) Protista 
A) Bacteria 
B) Fungi 
C) Archaea 
D) Protista

Question 7

MATCHING
Correctly match the definition with the correct geologic time period
-Carboniferous

Accepted Answer

A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya 
A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya

Question 8

Neighboring plant or fungi cells share a common cell wall,making multicellularity relatively simple.How do animal cells remain connected to one another?

Accepted Answer

A) Animal cells share a common plasma membrane rather than a common cell wall. 
B) Long interconnecting fibers extend from the nucleus of one cell to the nucleus of an adjacent cell. 
C) Most animals produce a fiber-rich extracellular matrix to which their cells can attach. 
D) Animal cells are connected to each other by the cytoskeleton. 
A) Animal cells share a common plasma membrane rather than a common cell wall. 
B) Long interconnecting fibers extend from the nucleus of one cell to the nucleus of an adjacent cell. 
C) Most animals produce a fiber-rich extracellular matrix to which their cells can attach. 
D) Animal cells are connected to each other by the cytoskeleton.

Question 9

In an evolutionary tree,a given ancestor and all its descendants make up a ________,or branch.

Accepted Answer

The answer of In an evolutionary tree,a given ancestor and...

Question 10

MATCHING
Correctly match the definition with the correct geologic time period
-Permian

Accepted Answer

A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya 
A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya

Question 11

The Cambrian explosion occurred primarily in the oceans.Which of the following were the first challenges that had to be overcome during the mass colonization of dry land in the Ordovician period?

Accepted Answer

A) support of body structure without buoyancy in water,movement,and reproduction 
B) photosynthesis,cellular respiration,and reproduction 
C) DNA replication,photosynthesis,and cellular respiration 
D) DNA replication,phagocytosis,and cellular respiration 
A) support of body structure without buoyancy in water,movement,and reproduction 
B) photosynthesis,cellular respiration,and reproduction 
C) DNA replication,photosynthesis,and cellular respiration 
D) DNA replication,phagocytosis,and cellular respiration

Question 12

MATCHING
Correctly match the definition with the correct geologic time period
-Silurian

Accepted Answer

A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya 
A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya

Question 13

MATCHING
Correctly match the definition with the correct geologic time period
-Cretaceous

Accepted Answer

A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya 
A) repeated advance and retreat of glaciers; evolution of humans; extinction of large mammals and birds; 0-2.6 mya 
B) continents begin to separate; diverse dinosaurs; first birds; first flowering plants; 145-200 mya 
C) extensive forests; amphibians dominate life on land; increase in diversity of insects; first reptiles; 300-360 mya 
D) further increases in diversity of marine invertebrates and vertebrates; plants and fungi begin to colonize land; mass extinction at end of period; 445-490 mya 
E) origin of life; photosynthesis causes oxygen content of Earth's atmosphere to increase; first eukaryotes; first multicellular organisms; 540 mya-3.8 bya
F)continents near present positions; increased diversity of flowering plants, birds, mammals, and pollinating insects; 2.6-65 mya
G)early dinosaurs; first mammals; mass extinction at end of period; 200-250 mya
H)increase in diversity of land plants; first amphibians colonize land; mass extinction late in period; 360-415 mya
I)large and relatively sudden increase in the diversity of animal life; increase in diversity of algae; first vertebrates; 490-540 mya
J)flowering plants begin to dominate life on land; mass extinction at end of period, including extinction of the last dinosaurs; 65-145 mya
K)continents come together to form Pangaea; reptiles dominate life on land by 265 mya; mass extinction at end of period; 250-300 mya
L)increase in diversity of fishes; first hints of colonization of land by insects and other invertebrates; 415-445 mya

Question 14

What criteria best characterize membership in the kingdom Protista?

Accepted Answer

A) a continuous lineage of descent from a common ancestor 
B) a large assortment of unique shared derived traits 
C) a common evolutionary heritage 
D) the inability to meet the characteristics that define each of the remaining eukaryotic kingdoms 
A) a continuous lineage of descent from a common ancestor 
B) a large assortment of unique shared derived traits 
C) a common evolutionary heritage 
D) the inability to meet the characteristics that define each of the remaining eukaryotic kingdoms

Question 15

The mass extinction at the end of the Permian period (about 250 mya)is thought to have killed off as many as 60 percent of the animal families.What group of animals dominated life on land at that time?

Accepted Answer

A) trilobites 
B) mammals 
C) reptiles 
D) amphibians 
A) trilobites 
B) mammals 
C) reptiles 
D) amphibians

Question 16

The mass extinction at the end of the Cretaceous period about 65 mya is believed to have been caused by a massive comet or asteroid smashing into what is now known as the Yucatan peninsula in the Gulf of Mexico.The debris arising from this impact would have blocked the Sun's rays from reaching the Earth.How would this cause a mass extinction?

Accepted Answer

A) With no sunlight,the plants would not be able to photosynthesize food for themselves,and they would die.Any animals that fed on those plants would also die,and any animals that would have eaten those animals would also now starve to death.This chain reaction would continue up the food chain. 
B) A giant fireball would have spontaneously incinerated every living thing,and the evolution of life on Earth would have started completely fresh. 
C) A massive wave spread out from the epicenter of the impact and drowned all of the terrestrial life on Earth.Evolution of all life on land started over after that event. 
D) All of the terrestrial plants and animals choked to death on the debris cloud. 
A) With no sunlight,the plants would not be able to photosynthesize food for themselves,and they would die.Any animals that fed on those plants would also die,and any animals that would have eaten those animals would also now starve to death.This chain reaction would continue up the food chain. 
B) A giant fireball would have spontaneously incinerated every living thing,and the evolution of life on Earth would have started completely fresh. 
C) A massive wave spread out from the epicenter of the impact and drowned all of the terrestrial life on Earth.Evolution of all life on land started over after that event. 
D) All of the terrestrial plants and animals choked to death on the debris cloud.

Question 17

Which kind of organism makes up the oldest fossil found on Earth?

Accepted Answer

A) protists 
B) animals 
C) bacteria 
D) plants 
A) protists 
B) animals 
C) bacteria 
D) plants

Question 18

The domain ________ encompasses the traditional four kingdoms of Protista,Plantae,Fungi,and Animalia.

Accepted Answer

The answer of The domain ________ encompasses the traditional four...

Question 19

You are a marine biologist who has isolated a microorganism from the Gulf of Mexico.This organism is unicellular,photosynthetic,uses a flagellum to swim,and you have observed it ingesting smaller microorganisms in its vicinity.To what kingdom does this organism most likely belong?

Accepted Answer

A) Fungi 
B) Animalia 
C) Plantae 
D) Protista 
A) Fungi 
B) Animalia 
C) Plantae 
D) Protista

Question 20

How was the distribution of humans (after they evolved)affected by continental drift?

Accepted Answer

A) The supercontinent of Pangaea had not yet split up before humans evolved.This made it very easy for humans to travel over the entire landmass of Earth. 
B) The supercontinent of Pangaea had already begun to split up,but the continents were still very close together making it pretty easy for humans to travel from one continent to another. 
C) The supercontinent of Pangaea had not yet split up before humans evolved.This had little impact on the distribution of humans because they did not travel until the 1400s. 
D) The supercontinent of Pangaea split apart and the resulting continents were pretty much in their present day locations by the time modern humans evolved.This would have slowed the distribution of humans until they developed ways of easily traversing the oceans. 
A) The supercontinent of Pangaea had not yet split up before humans evolved.This made it very easy for humans to travel over the entire landmass of Earth. 
B) The supercontinent of Pangaea had already begun to split up,but the continents were still very close together making it pretty easy for humans to travel from one continent to another. 
C) The supercontinent of Pangaea had not yet split up before humans evolved.This had little impact on the distribution of humans because they did not travel until the 1400s. 
D) The supercontinent of Pangaea split apart and the resulting continents were pretty much in their present day locations by the time modern humans evolved.This would have slowed the distribution of humans until they developed ways of easily traversing the oceans.

Evolutionary trees are continually revised by scientists as new information becomes available from various sources such as

Although it is costly to produce fruit,the large number of fruit-producing plant species attests to its success as an evolutionary adaptation.In what way is fruit production helpful to plants?

Identify key characteristics for kingdom Fungi and provide three examples of members of this kingdom.

Gymnosperms and angiosperms are believed to be more closely related to one another than the other major plant groups because

The fourth mass extinction occurred about 200 mya at the end of the period.This extinction eliminated 35 percent of the existing animal species including .

Resolving the relationship between the various kingdoms has been challenging because species often resemble one another.For example,the kingdom ________ contains some organisms that are animal-like and others that are plantlike.

MATCHING Correctly match the definition with the correct geologic time period -Carboniferous

Neighboring plant or fungi cells share a common cell wall,making multicellularity relatively simple.How do animal cells remain connected to one another?

In an evolutionary tree,a given ancestor and all its descendants make up a ________,or branch.

MATCHING Correctly match the definition with the correct geologic time period -Permian

The Cambrian explosion occurred primarily in the oceans.Which of the following were the first challenges that had to be overcome during the mass colonization of dry land in the Ordovician period?

MATCHING Correctly match the definition with the correct geologic time period -Silurian

MATCHING Correctly match the definition with the correct geologic time period -Cretaceous

What criteria best characterize membership in the kingdom Protista?

The mass extinction at the end of the Permian period (about 250 mya)is thought to have killed off as many as 60 percent of the animal families.What group of animals dominated life on land at that time?

Which kind of organism makes up the oldest fossil found on Earth?

The domain ________ encompasses the traditional four kingdoms of Protista,Plantae,Fungi,and Animalia.

You are a marine biologist who has isolated a microorganism from the Gulf of Mexico.This organism is unicellular,photosynthetic,uses a flagellum to swim,and you have observed it ingesting smaller microorganisms in its vicinity.To what kingdom does this organism most likely belong?

How was the distribution of humans (after they evolved)affected by continental drift?

The Nature of Science

Chemistry of Life

Life Is Cellular

How Cells Work

Cell Division

Patterns of Inheritance

Chromosomes and Human Genetics

What Genes Are

How Genes Work

Evidence for Evolution

Mechanisms of Evolution

Adaptation and Species

Human Evolution

General Principles of Ecology

Growth of Populations

Communities of Organisms

Ecosystems

Applying the Science

Filters

Exam 13: The History of Life

Evolutionary trees are continually revised by scientists as new information becomes available from various sources such as

Although it is costly to produce fruit,the large number of fruit-producing plant species attests to its success as an evolutionary adaptation.In what way is fruit production helpful to plants?

Identify key characteristics for kingdom Fungi and provide three examples of members of this kingdom.

Gymnosperms and angiosperms are believed to be more closely related to one another than the other major plant groups because

The fourth mass extinction occurred about 200 mya at the end of the ________ period.This extinction eliminated 35 percent of the existing animal species including ________.

Resolving the relationship between the various kingdoms has been challenging because species often resemble one another.For example,the kingdom ________ contains some organisms that are animal-like and others that are plantlike.

MATCHING Correctly match the definition with the correct geologic time period -Carboniferous

Neighboring plant or fungi cells share a common cell wall,making multicellularity relatively simple.How do animal cells remain connected to one another?

In an evolutionary tree,a given ancestor and all its descendants make up a ________,or branch.

MATCHING Correctly match the definition with the correct geologic time period -Permian

The Cambrian explosion occurred primarily in the oceans.Which of the following were the first challenges that had to be overcome during the mass colonization of dry land in the Ordovician period?

MATCHING Correctly match the definition with the correct geologic time period -Silurian

MATCHING Correctly match the definition with the correct geologic time period -Cretaceous

What criteria best characterize membership in the kingdom Protista?

The mass extinction at the end of the Permian period (about 250 mya)is thought to have killed off as many as 60 percent of the animal families.What group of animals dominated life on land at that time?

Which kind of organism makes up the oldest fossil found on Earth?

The domain ________ encompasses the traditional four kingdoms of Protista,Plantae,Fungi,and Animalia.

You are a marine biologist who has isolated a microorganism from the Gulf of Mexico.This organism is unicellular,photosynthetic,uses a flagellum to swim,and you have observed it ingesting smaller microorganisms in its vicinity.To what kingdom does this organism most likely belong?

How was the distribution of humans (after they evolved)affected by continental drift?

The Nature of Science

Chemistry of Life

Life Is Cellular

How Cells Work

Cell Division

Patterns of Inheritance

Chromosomes and Human Genetics

What Genes Are

How Genes Work

Evidence for Evolution

Mechanisms of Evolution

Adaptation and Species

Human Evolution

General Principles of Ecology

Growth of Populations

Communities of Organisms

Ecosystems

Applying the Science

Filters

The fourth mass extinction occurred about 200 mya at the end of the period.This extinction eliminated 35 percent of the existing animal species including .