Chapter 32: An Introduction To Animal Diversity
Chapter 32 – An Introduction to Animal Diversity
All animals share a common ancestor, sponges are basal animals, eumetazoa is a clade of animals with true tissues, most animal phyla belong to the clade bilateria, and vertebrates and some other phyla belong Animals share a unique homeobox-containing family of genes, known as the Hox genes, suggesting that this gene family evolved in the eukaryote lineage that gave rise to animals. Hox genes play important roles in the development of animal embryos, controlling the expression of dozens or even hundreds of other genes. Hox genes can thus control cell division and differentiation producing different morphological features of animals.
Some calculations based on molecular clocks estimate that the ancestors of animals diverged from the ancestors of fungi as far back as 1.5 billion years ago.
The Cambrian explosion is a period where animal diversification appears to have accelerated dramatically between 542 and 525 million years ago. The first hypothesis is that new predator-prey relationships that emerged in the Cambrian period generated diversity through natural selection. The second hypothesis focuses on the rise in athmospheric oxygen that preceded the Cambrian explosion. The third hypothesis holds that the evolution of the Hox gene complex provided the …show more content…
Ecdysozoa secrete external skeletons. As the animal grows, it molts. Though named for molting, the clade is actually defined mainly by molecular evidence supporting the common ancestry of its members. The name Lophotrochozoa refers to two different structures observed in animals belonging to this clade. Some animals develop a structure called a lophophore, a crown of ciliated tentacles that function in feeding. Other phyla, including annelids and molluscs go through a distinctive larval stage called the trochophore
All animals share a common ancestor, sponges are basal animals, eumetazoa is a clade of animals with true tissues, most animal phyla belong to the clade bilateria, and vertebrates and some other phyla belong Animals share a unique homeobox-containing family of genes, known as the Hox genes, suggesting that this gene family evolved in the eukaryote lineage that gave rise to animals. Hox genes play important roles in the development of animal embryos, controlling the expression of dozens or even hundreds of other genes. Hox genes can thus control cell division and differentiation producing different morphological features of animals.
Some calculations based on molecular clocks estimate that the ancestors of animals diverged from the ancestors of fungi as far back as 1.5 billion years ago.
The Cambrian explosion is a period where animal diversification appears to have accelerated dramatically between 542 and 525 million years ago. The first hypothesis is that new predator-prey relationships that emerged in the Cambrian period generated diversity through natural selection. The second hypothesis focuses on the rise in athmospheric oxygen that preceded the Cambrian explosion. The third hypothesis holds that the evolution of the Hox gene complex provided the …show more content…
Ecdysozoa secrete external skeletons. As the animal grows, it molts. Though named for molting, the clade is actually defined mainly by molecular evidence supporting the common ancestry of its members. The name Lophotrochozoa refers to two different structures observed in animals belonging to this clade. Some animals develop a structure called a lophophore, a crown of ciliated tentacles that function in feeding. Other phyla, including annelids and molluscs go through a distinctive larval stage called the trochophore