General Biology 2: Modules 5

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Questions and Answers

What is the characteristic of radial symmetry in animals?

Having a right and left side, anterior and posterior end

Having a dorsal and ventral side

Having a front and back, nor left and right (correct)

Having a brain, concentrated in their anterior end

Which group of animals lack a true body cavity?

Bilaterians

Coelomates

Acoelomates (correct)

Pseudocoelomates

What is the name of the clade that includes animals with true tissues?

Deuterostomia

Eumetazoa (correct)

Protostomia

Bilateria

Which type of cleavage is characterized by each cell retaining the capacity to develop into a complete embryo?

Indeterminate cleavage Signup and view all the answers

What is the name of the clade that includes animals that shed their exoskeletons through a process called ecdysis?

Ecdysozoa Signup and view all the answers

Which of the following is a characteristic of bilaterally symmetrical animals?

Having a dorsal and ventral side, a right and left side, and anterior and posterior end Signup and view all the answers

What is the name of the body cavity that is derived from the mesoderm and endoderm?

Pseudocoelom Signup and view all the answers

Which of the following is a characteristic of deuterostome development?

Involve both mesoderm and archenteron Signup and view all the answers

What is the name of the clade that includes animals that have a feeding structure called a lophophore?

Lophotrochozoa Signup and view all the answers

What is the name of the larval stage that is characteristic of lophotrochozoans?

Trochophore larva Signup and view all the answers

What is the primary effect of the oxygen revolution on prokaryotic groups?

They became extinct due to oxygen toxicity Signup and view all the answers

What is the significance of choanoflagellates in the context of animal evolution?

They are the closest relatives of modern animals Signup and view all the answers

What is the characteristic of bilaterian animals that distinguishes them from other animals?

They have a two-sided body plan with bilateral symmetry Signup and view all the answers

What is the primary factor that contributed to the Cambrian explosion?

The development of new predator-prey relationships Signup and view all the answers

What is the significance of the endosymbiotic theory in the context of eukaryotic evolution?

It explains the origin of mitochondria and plastids Signup and view all the answers

Which of the following phyla is characterized by the presence of a water vascular system?

Echinodermata Signup and view all the answers

What is the characteristic of animals that is thought to have contributed to their diversification and success?

The development of a central nervous system Signup and view all the answers

What is the main function of the pharyngeal slits in vertebrates?

Gas exchange Signup and view all the answers

Which of the following groups of animals is characterized by the presence of a notochord and a dorsal, hollow nerve cord?

Chordata Signup and view all the answers

What is the estimated rate of extinction in the current era?

100 to 1,000 times the typical background rate Signup and view all the answers

What is the main function of the post-anal tail in chordates?

Propelling the body Signup and view all the answers

What is the primary cause of the mass extinctions that occurred in the Earth's history?

All of the above Signup and view all the answers

Which of the following phyla is characterized by the presence of a coelom and a segmented body?

Annelida Signup and view all the answers

What is the significance of the Cambrian period in the context of animal evolution?

It marks the diversification of animal body plans Signup and view all the answers

What is the characteristic of the Cenozoic era that distinguishes it from the preceding eras?

The cooling of the global climate Signup and view all the answers

What is the main function of the lophophores in lophophorates?

Feeding Signup and view all the answers

Which of the following groups of animals is characterized by the presence of a pseudocoelom and a alimentary canal?

Rotifera Signup and view all the answers

What is the main function of the notochord in chordates?

Providing skeletal support Signup and view all the answers

Which of the following phyla is characterized by the presence of a hard shell made of calcium carbonate?

Mollusca Signup and view all the answers

Which of the following groups of animals is characterized by the presence of a hollow nerve cord and pharyngeal slits?

Chordata Signup and view all the answers

What is the characteristic of the blastula stage?

It is a multicellular, hollow stage Signup and view all the answers

What is the function of Hox genes in animals?

They regulate the development of body form Signup and view all the answers

What is the characteristic of larval stages in animals?

They are morphologically distinct from the adult Signup and view all the answers

What is the term for the process of cell division that occurs after fertilization?

Cleavage Signup and view all the answers

What is the term for the formation of different layers of embryonic tissues?

Gastrulation Signup and view all the answers

What is the characteristic of animal cells?

They are multicellular eukaryotes Signup and view all the answers

What is the term for the study of the history of life on Earth?

Fossil Record Signup and view all the answers

What is the term for the process of determining the absolute ages of fossils?

Radiometric Dating Signup and view all the answers

What is the characteristic of sedimentary rocks?

They are deposited into layers called strata Signup and view all the answers

What is the term for the period of time that includes the last half billion years?

Phanerozoic Eon Signup and view all the answers

Study Notes

Characteristics of Animals

Animals are multicellular, heterotrophic eukaryotes that reproduce sexually with the diploid stage usually dominating the life cycle.
They have tissues that develop from embryonic layers and are mobile, using traits such as strength, speed, toxins, or camouflage to detect, capture, and eat other organisms.

Cell Structure and Specialization of Animals

Animal cells are multicellular eukaryotes with no cell walls, and their bodies are held together by structural proteins such as collagen.
Nervous tissue and muscle tissue are unique, defining characteristics of animals.

Reproduction and Development of Animals

Most animals have at least one larval stage that is sexually immature and morphologically distinct from the adult.
The larva eventually undergoes metamorphosis to become a juvenile, which resembles an adult but is not yet sexually mature.
Homeotic genes, such as Hox genes, provide positional information during animal embryonic development and regulate the development of body form.

History of Animals

The history of animals spans more than half a billion years.
The geologic record is divided into Hadean, Archaean, Proterozoic, and Phanerozoic eons.
More than 1.3 million animal species have been named to date, with far more estimated to exist.
The common ancestor of all living animals likely lived between 700 and 770 million years ago.

Fossil Record

The Fossil Record documents the history of life on Earth, revealing changes in the history of life over time.
Sedimentary rocks are the richest source of fossils and are deposited into layers called strata.
Radioactive dating is used to determine the absolute ages of fossils.

Developmental Biology

Cleavage is the cell division that the zygote undergoes after a sperm fertilizes an egg, leading to the formation of a multicellular, hollow blastula.
The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues.
Paralogues are two segments of DNA that share ancestral genes, and they can produce a wide diversity of animal morphology.### The History of Life on Earth
The Earth is approximately 4.5 billion years old, and life on Earth is believed to have originated around 3.5 billion years ago.
The history of life on Earth is divided into three eras: Paleozoic, Mesozoic, and Cenozoic.

The Oxygen Revolution

Around 2.7 billion years ago, oxygen began to accumulate in the atmosphere, causing the extinction of many prokaryotic groups.
Some prokaryotic groups survived and adapted to the oxygen-rich environment using cellular respiration.

The Origin of Multicellularity

The oldest fossils of eukaryotic cells date back to 1.8 billion years ago.
Eukaryotes have a nuclear envelope, mitochondria, endoplasmic reticulum, and a cytoskeleton.
The endosymbiotic theory suggests that the prokaryotic ancestors of mitochondria and plastids gained entry to the host cell as undigested prey or internal parasites.

The Neoproterozoic Era

During this era, multicellular eukaryotes were formed, and animals, plants, and fungi began to colonize land.
The Ediacaran biota, which lived around 560 million years ago, consisted of larger and more diverse soft-bodied organisms.

The Cambrian Explosion

The Cambrian explosion, which occurred around 535-525 million years ago, marked the sudden appearance of fossils resembling modern animal phyla.
The Cambrian explosion also refers to the diversification of animals, including the origin of bilateral symmetry.

The Mesozoic Era

The Mesozoic era, which lasted from 251-65.5 million years ago, saw the rise of dinosaurs as the dominant terrestrial vertebrates.
The first mammals emerged during this era.

The Cenozoic Era

The Cenozoic era, which began 65.5 million years ago, followed the mass extinctions of both terrestrial and marine animals.
Mammals increased in size and exploited vacated ecological niches.

The Six Mass Extinction Events

There have been five major mass extinction events in the history of life on Earth, with the most recent one occurring 65.5 million years ago.
A sixth, human-caused mass extinction is likely to occur unless dramatic action is taken.

Animal Body Plans

Animals can be characterized by their body plans, which include developmental and morphological traits.
Body plans have been conserved in some groups, while others have changed multiple times over the course of evolution.

Symmetry

Animals can be categorized based on the symmetry of their bodies, or lack of it.
Radial symmetry, with no front and back, nor left and right, is found in some animals.
Bilateral symmetry, with a dorsal (top) and ventral (bottom) side, and a right and left side, is found in many animals.

Body Cavities

Coelomates possess a true body cavity, which is derived from the mesoderm.
Pseudocoelomates possess a pseudocoelom, which is derived from the mesoderm and endoderm.
Acoelomates lack a body cavity.

Development

Protostome and deuterostome development differ based on the early development of the animal.
Indeterminate cleavage, where each cell in the early stages of cleavage retains the capacity to develop into a complete embryo, is found in some animals.
Coelom formation and the fate of the blastophore also differ between protostomes and deuterostomes.

The Diversification of Animals

Zoologists recognize around three dozen animal phyla.
Phylogenies combine morphological, molecular, and fossil data to understand the relationships among living animals.
Five important points about the relationships among living animals are reflected in their phylogeny:
- All animals share a common ancestor.
- Sponges are basal animals.
- There are three major clades of bilaterian animals.
- The bilaterians are divided into three clades: deuterostomia, ecdysozoa, and lophotrochozoa.### Invertebrates
Invertebrates are animals that lack a backbone.
They account for more than 95% of known animal species.
They are morphologically diverse and occupy almost every habitat on Earth.

Deuterostomia Examples

Phylum Chordata: Coelomates with notochord; dorsal, hollow nerve cord; pharyngeal slits; and post-anal tail.
Phylum Echinodermata: Coelomates with bilateral symmetry; unique water vascular system; and have an endoskeleton.

Lophotrochozoa Examples

Phylum Platyhelminthes: Acoelomates with poroventrally flattened body; no digestive tract.
Phylum Rotifera: Pseudocoelomates with alimentary canal (digestive tube with mouth and anus).
Phylum Lophophorates: Coelomates with lophophores (feeding structures bearing ciliated tentacles).
Phylum Mollusca: Coelomates with 3 main body parts (muscular foot, visceral mass, and mantle) and coelom reduced.
Phylum Annelida: Coelomates with segmented body and internal organs (except digestive tract).

Chordates

Chordates share a set of derived characters.
There are four key characters of chordates:
- Notochord: A longitudinal, flexible rod between the digestive tube and nerve cord, providing skeletal support throughout most of the length of a chordate.
- Dorsal, Hollow Nerve Cord: Developed from a plate of ectoderm that rolls into a tube dorsal to the notochord.
- Pharyngeal Slits or Clefts: Grooves in the pharynx that develop into slits that open to the outside of the body, serving various functions in different species.
- Muscular, Post-Anal Tail: A tail posterior to the anus, containing skeletal elements and muscles, and providing propelling force in many aquatic species.

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Description

This quiz covers modules 5 of General Biology 2, focusing on the evolution and diversity of animals, including their characteristics and life cycles.