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 membranebound 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.