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The ratio of brain volume to body mass in humans is roughly

2.5 times the brain volume to body mass ratio in chimpanzees, our closest primate relatives.

Most animals have muscle cells for movement and nerve cells that.

control the muscles

Our closest anthropoid relatives are the nonhuman apes:

gibbons, orangutans, gorillas, and chimpanzees, which live only in tropical regions of the Old World.

Although body size has remained roughly the same for about the last 1.5 million years of human evolution, brain size has increased by about

40%.

Animal diversification appears to have accelerated rapidly from

525 to 535 million years ago, during the Cambrian period.

the oldest animal fossils that have been found are about

560 million years old.

Animal life began in Precambrian seas with the evolution of multicellular creatures that ate other organisms.

Animals are eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by eating, and are able to digest the food within their bodies.

Historically, biologists have categorized animals by

Body plan

Because so many animal body plans and new phyla appear in the fossils from such an evolutionarily short time span, biologists call this episode the

Cambrian explosion

Which phylum is most closely related to chordata

Echinoderm

What makes humans such successful animals?

Much of our success is due to brain power

What is an Animal? •

Most animals -are diploid, -reproduce sexually, and -proceed through basic stages found in most animal life cycles.

Misconceptions about human evolution persist.

One of these myths is the question "If chimpanzees were our ancestors, then why do they still exist?"

What ignited the Cambrian explosion?

Scientists have proposed several hypotheses, including increasingly complex predator-prey relationships and an increase in atmospheric oxygen

Taxonomists divide the primates into three main groups.

The first group of primates lives in Madagascar, southern Asia, and Africa and includes lemurs, lorises, and bush babies. 2.Tarsiers, small nocturnal tree-dwellers found only in Southeast Asia, form the second group of primates. 3.The third group, anthropoids, includes monkeys and apes. Anthropoids also have a fully opposable thumb; that is, they can touch the tips of all four fingers with their thumb.

master control genes

The relationship of structure to function 2.Information flow 3.Pathways that transform energy and matter 4.Interactions within biological systems 5.Evolution

Humans are just one of the 1.3 million species of animals named and described by biologists.

This amazing diversity arose through hundreds of millions of years of evolution as natural selection shaped animal adaptations to Earth's many environments.

Scientists hypothesize that animals evolved from a

colonial flagellated protist.

master control genes

homeotic genes

In a sea star life cycle, the larva undergoes a major change of body form, called

metamorphosis, in becoming an adult capable of reproducing sexually.

The part of our brain that deals with problem solving, language, logic, and understanding other people is

particularly well developed.

body plans were used to construct

phylogenetic trees

Animal cells lack the cell walls that provide strong support in the bodies of.

plants and fungi