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What is the characteristic of radial symmetry in animals?
Which group of animals lack a true body cavity?
What is the name of the clade that includes animals with true tissues?
Which type of cleavage is characterized by each cell retaining the capacity to develop into a complete embryo?
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What is the name of the clade that includes animals that shed their exoskeletons through a process called ecdysis?
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Which of the following is a characteristic of bilaterally symmetrical animals?
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What is the name of the body cavity that is derived from the mesoderm and endoderm?
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Which of the following is a characteristic of deuterostome development?
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What is the name of the clade that includes animals that have a feeding structure called a lophophore?
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What is the name of the larval stage that is characteristic of lophotrochozoans?
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What is the primary effect of the oxygen revolution on prokaryotic groups?
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What is the significance of choanoflagellates in the context of animal evolution?
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What is the characteristic of bilaterian animals that distinguishes them from other animals?
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What is the primary factor that contributed to the Cambrian explosion?
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What is the significance of the endosymbiotic theory in the context of eukaryotic evolution?
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Which of the following phyla is characterized by the presence of a water vascular system?
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What is the characteristic of animals that is thought to have contributed to their diversification and success?
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What is the main function of the pharyngeal slits in vertebrates?
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Which of the following groups of animals is characterized by the presence of a notochord and a dorsal, hollow nerve cord?
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What is the estimated rate of extinction in the current era?
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What is the main function of the post-anal tail in chordates?
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What is the primary cause of the mass extinctions that occurred in the Earth's history?
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Which of the following phyla is characterized by the presence of a coelom and a segmented body?
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What is the significance of the Cambrian period in the context of animal evolution?
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What is the characteristic of the Cenozoic era that distinguishes it from the preceding eras?
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What is the main function of the lophophores in lophophorates?
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Which of the following groups of animals is characterized by the presence of a pseudocoelom and a alimentary canal?
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What is the main function of the notochord in chordates?
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Which of the following phyla is characterized by the presence of a hard shell made of calcium carbonate?
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Which of the following groups of animals is characterized by the presence of a hollow nerve cord and pharyngeal slits?
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What is the characteristic of the blastula stage?
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What is the function of Hox genes in animals?
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What is the characteristic of larval stages in animals?
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What is the term for the process of cell division that occurs after fertilization?
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What is the term for the formation of different layers of embryonic tissues?
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What is the characteristic of animal cells?
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What is the term for the study of the history of life on Earth?
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What is the term for the process of determining the absolute ages of fossils?
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What is the characteristic of sedimentary rocks?
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What is the term for the period of time that includes the last half billion years?
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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
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Zoologists recognize around three dozen animal phyla.
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Phylogenies combine morphological, molecular, and fossil data to understand the relationships among living animals.
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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
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Invertebrates are animals that lack a backbone.
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They account for more than 95% of known animal species.
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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.
