Cambrian Period Evolution

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Questions and Answers

What is the proposed role of Hox genes and other genetic changes in the evolution of new body forms?

They led to the extinction of arthropods

They facilitated the origin of vertebrates

They affected the regulation of developmental genes (correct)

They triggered the Cambrian explosion

What is the significance of fern galls in understanding the evolution of insects and plants?

They demonstrate the influence of insects and plants on each other's evolution (correct)

They mark the origin of amphibians

They indicate the diversification of arthropods

They provide evidence of vertebrate evolution

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

It is a period of stable evolution

It is a period of rapid animal diversification (correct)

It is a period of mass extinction

It marks the origin of vertebrates

What is the distinction between amphibians and amniotes?

Amphibians have a larval stage, while amniotes do not Signup and view all the answers

What is the estimated time when vertebrates transitioned to land?

365 million years ago Signup and view all the answers

What is the inferred relationship between arthropods and terrestrial habitats during the Cambrian period?

Arthropods began to adapt to terrestrial habitats during the Cambrian period Signup and view all the answers

What is the primary characteristic that distinguishes animals from plants and fungi?

Heterotrophy Signup and view all the answers

Which of the following is a key feature of animal development?

Formation of embryonic tissue layers Signup and view all the answers

What is the term for the process by which animals develop body form and structure?

Hox gene regulation Signup and view all the answers

Which of the following time periods is characterized by the diversification of mammals?

Cenozoic era Signup and view all the answers

What is the term for the description of an animal's overall body structure and organization?

Body plan Signup and view all the answers

Which of the following types of symmetry is characteristic of some animals?

All of the above Signup and view all the answers

What is the primary difference between the formation of coelom in protostome and deuterostome development?

Protostomes form coelom from the splitting of solid mesoderm, while deuterostomes form it from the mesoderm budding from the archenteron Signup and view all the answers

What is the term for a group of organisms that share a common ancestor and all of its descendants?

Clade Signup and view all the answers

Which of the following phyla is characterized by radial symmetry and diploblastic body structure?

Cnidaria Signup and view all the answers

What is the term for animals that have true tissues?

Eumetazoa Signup and view all the answers

According to the phylogenetic trees, what is the relationship between sponges and other animal lineages?

Sponges are basal and branch from the base of both animal trees Signup and view all the answers

What is the common characteristic shared by worms, humans, and most other triploblasts, despite their differences in specific anatomy?

A doughnut-like shape Signup and view all the answers

What is the primary function of hemolymph in the body cavity of certain triploblastic animals?

Transport nutrients and waste throughout the body Signup and view all the answers

What is the key difference between radial cleavage in deuterostomes and spiral cleavage in protostomes?

Radial cleavage occurs in deuterostomes, while spiral cleavage occurs in protostomes Signup and view all the answers

What is the term for the blind pouch that forms during gastrulation and eventually becomes the gut?

Archenteron Signup and view all the answers

What is the common ancestor of all animals, according to the current understanding of animal phylogeny?

A common ancestor of all animals Signup and view all the answers

What is the characteristic that distinguishes Eumetazoa from other animals?

Presence of tissues Signup and view all the answers

In which group of animals does the blastopore become the anus?

Deuterostomes Signup and view all the answers

Study Notes

Body Cavity and Development

A coelom is a body cavity surrounded by tissues derived from mesoderm, which forms structures that suspend internal organs.
A hemocoel is a body cavity formed between the mesoderm and endoderm, filled with hemolymph that transports nutrients and waste throughout the body cavity.
Some triploblastic animals lack a body cavity, being compact with thin, flat bodies that exchange nutrients, gases, and wastes across the body surface.

Protostome and Deuterostome Development

Protostome development is characterized by spiral and determinant cleavage, where cell fate is rigidly determined early on.
Deuterostome development is characterized by radial and indeterminate cleavage, where each cell produced by early cleavage can form a complete embryo.

Coelom Formation

Coelom formation occurs during gastrulation, where the embryo forms a blind pouch, the archenteron (which becomes the gut).
In protostome development, the coelom forms from the splitting of solid masses of mesoderm.
In deuterostome development, the coelom forms from the mesoderm budding from the wall of the archenteron.

Fate of the Blastopore

The blastopore is an indentation in the gastrula that leads to the formation of the archenteron.
In protostome development, the blastopore becomes the mouth.
In deuterostome development, the blastopore becomes the anus.

Animal Phylogeny

By 500 million years ago, most animal phyla with members alive today were established.
Multiple data sources, including whole genomes, morphological traits, rRNA genes, Hox genes, protein-coding nuclear genes, and mitochondrial genes, are used to infer evolutionary relationships among animal phyla.

Diversification of Animals

All animals share a common ancestor.
Sponges are the sister group to all other animals.
Eumetazoa is a clade of animals with tissues, including all animals except sponges and a few others.
Most animal phyla belong to the clade Bilateria.
Bilateria includes both invertebrates and vertebrates, with Chordata being the only phylum that includes vertebrates.

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Description

Explore the theories behind the rapid evolution of life forms during the Cambrian period, including Hox genes and developmental gene regulation.