Biologist ______Date ______
PowerPoint 25-1: What is an Animal?
Characteristics of Animals
Animals are all ______; they obtain nutrients and energy by eating other organisms.
Animals are also ______; their bodies are composed of many cells.
The cells that make up animal bodies are ______, containing a nucleus and membrane-bound organelles.
Unlike the cells of algae, fungi, and plants, animal cells lack cell ______.
Invertebrates
Invertebrates include all animals that lack a ______, or vertebral column.
More than _____ percent of animal species are informally called invertebrates. Invertebrates include at least 33 phyla.
Invertebrates include sea stars, worms, jellyfishes, and ______, like butterflies.
They range in size from dust mites to giant ______more than 20 meters long.
Chordates
Fewer than 5 percent of animal species are chordates, members of the clade commonly known as ______Chordata.
All chordates exhibit four characteristics during at least one stage of life: a dorsal, hollow nerve ___; a ______; a ______that extends beyond the anus; and pharyngeal ______.
The hollow nerve cord runs along the dorsal (back) part of the body. ______branch from this cord at intervals.
The notochord is a long supporting rod that runs through the body just below the nerve cord. Most chordates have a notochord only when they are ______.
At some point in their ______, all chordates have a tail that extends beyond the anus.
Pharyngeal pouches are paired structures in the throat region, which is also called the ______.
In some chordates, such as fishes, slits develop that connect pharyngeal pouches to the outside of the body. The pharyngeal pouches may develop into gills used for ______exchange.
Most chordates develop a ______, or vertebral column, constructed of bones called vertebrae.
Chordates with backbones are called vertebrates and include ______, ______, ______, ______, and ______.
Maintaining Homeostasis
All organisms must keep their internal environment relatively stable, a process known as maintaining ______. In animals, maintaining homeostasis is the most important function of all body systems.
For example, reptiles, birds, and mammals cannot excrete ______. Those that spend time hunting or feeding in salt water, such as the marine iguana, have adaptations that allow them to remove salt from their bodies.
Marine iguanas maintain ______by sneezing a combination of salt and nasal mucus that sometimes coats their bumpy heads and spiny necks.
Often, homeostasis is maintained by feedback inhibition, or ______feedback, a system in which the product or result of a process limits the process itself.
For example, if you get too cold, you ______, using muscle activity to generate heat.
If you get too hot, you ______, which helps you lose heat.
Gathering and Responding to Information
The nervous system gathers information using cells called ______that respond to sound, light, chemicals, and other stimuli.
Other nerve cells collect and process that information and determine how to ______.
Some invertebrates have only a ______network of nerve cells, with no real center.
Other invertebrates and most chordates have large numbers of nerve cells concentrated into a _____.
Animals often respond to the information processed in their nervous system by ______.
Muscle tissue generates force by becoming shorter when ______by the nervous system.
Muscles work together with some kind of supporting structure called a skeleton to make up the ______system.
______vary widely from phylum to phylum.
Some invertebrates, such as earthworms, have skeletons that are flexible and function through the use of ______pressure.
Insects and some other invertebrates have ______skeletons. The hard shell of a lobster is an external skeleton.
The bones of vertebrates form an internal skeleton. Your ______are part of your internal skeleton.
Obtaining and Distributing Oxygen and Nutrients
All animals must ______to obtain oxygen. Small animals that live in water or in wet places can “breathe” by allowing oxygen to ______across their skin.
Larger animals use a respiratory system based on one of many different kinds of ______, lungs, or air passages.
All animals must ______to obtain nutrients.
Most animals have a ______system that acquires food and breaks it down into forms cells can use.
After acquiring oxygen and nutrients, animals must transport them to cells throughout their bodies by using some kind of ______system.
The structures and functions of respiratory and digestive systems must ______together with circulatory systems.
Animals’ ______processes generate carbon dioxide and other waste products, some of which contain nitrogen in the form of ammonia.
Both carbon dioxide and ammonia are ______in high concentrations and must be excreted, or eliminated from the body.
Collecting and Eliminating CO2 and Other Wastes
Many animals eliminate ______by using their ______systems.
Most complex animals have a specialized organ system—the excretory system—for eliminating other wastes, such as ______.
The excretory system concentrates or processes these wastes and either expels them ______or stores them before eliminating them.
Before wastes can be discharged, the ______system must collect them from cells throughout the body and then deliver them to the respiratory or excretory system. The collection and elimination of wastes requires close interactions between these systems.
Reproducing
Most animals reproduce ______by producing ______.
Sexual reproduction helps create and maintain genetic ______, which increases a species’ ability to evolve and adapt as its environment changes.
Like many vertebrates, a pygmy marsupial frog ______for her young while they develop. Unlike most animals, she carries her eggs on her back.
Many invertebrates and a few vertebrates can also reproduce ______.
Asexual reproduction produces offspring that are genetically ______to the parent.
It allows animals to increase their ______rapidly but does not generate genetic diversity.