Download Chapter 30: Comparing Invertebrates

Chapter 30: Comparing Invertebrates
Section 2: Form and Function in Invertebrates
Form and Function in Invertebrates

Each animal phylum represents an experiment in the design of body structures to
perform the tasks ______________________________________________

The appearance of each phylum in the __________________________________
represents the random evolutionary development of a basic body plan that is
different in some way from other body plans

Evolution is ___________________ and _____________________________

Organisms are not better or worse than one another – they are simply different

The body systems that perform the vital functions of life have taken many
different forms in different phyla

Some are complex, others are simple

Some are efficient, others are not

More complicated and efficient systems are not necessarily __________________
than simpler systems
Movement

Almost all animals use specialized tissues called ________________________ to
move

Without muscles, animals could not swim, fly, burrow, or run

Muscles work only by _______________________________

When muscles are stimulated, they generate force by getting shorter

When they are not stimulated, they __________________

In most animals, muscles work together with some sort of skeletal system that
provides firm support

There are three main kinds of skeletal systems: ___________________________
___________________________, _______________________________, and
_________________________________
Hydrostatic Skeletons

Hydrostatic skeletons do not contain ___________________________________,
such as bones or chitin plates, for muscles to pull against

Instead, the muscles surround and are supported by a _______________________
_____________________ body cavity

When the muscles contract, they push against the water in the body cavity

Cnidarians, some flatworms, roundworms, some mollusks, and annelids have
hydrostatic skeletons
Exoskeletons

Exoskeletons usually refer to the _______________________________________
that encloses an arthropod’s internal organs and muscles

However, the shells of mollusks can also be considered exoskeletons

Muscles attached to the inside of an arthropod’s exoskeleton are used to
_____________________________________________________________

Muscles attached to the shell in mollusks make it possible for snails to withdraw
into their shell and for bivalves to close their two-part shell
Endoskeletons

Endoskeletons are frameworks located ______________________ the body of
animals

Sponges, echinoderms, and vertebrates have endoskeletons

Animals with endoskeletons typically have muscles that attach to the outside
surface of the endoskeleton
Feeding

As you move through the invertebrate phyla from simpler animals such as
sponges to more complex animals such as arthropods, you can observe three
major evolutionary trends

First, simpler animals such as sponges, cnidarians, and flatworms break down
their food primarily through __________________________________________

More complex animals use _______________________________________

In intracellular digestion food is digested, or broken down, inside the cells

In extracellular digestion, food is broken down outside the cells – specifically, in
a digestive tract

Mollusks, annelids, arthropods, echinoderms, and chordates typically rely on
extracellular digestion

Second, cnidarians and some flatworms have a ____________________________
______________________________________ that has a single opening through
which food enters and through which solid wastes are expelled

More advanced digestive systems, such as those found in roundworms, mollusks,
annelids, arthropods, echinoderms, and chordates, have _____________________
– a mouth at one end and an anus at the other

Third, the _____________________________________ tends to acquire more
and more specialized regions

The digestive system is not the only system to become more specialized as you
move from simpler animals to more complex animals

This evolutionary trend is seen in most of the other systems responsible for
performing essential life functions
Internal Transport

All cells of multicellular animals must be supplied with oxygen and nutrients and
must dispose of metabolic wastes

The smallest and thinnest multicellular animals manage to fulfill their internal
transport needs through __________________________ between their body
surface and the environment

Most complex multicellular animals have a collection of pumps and tubes called a
________________________________________

There are two basic types of circulatory systems: __________________________
Respiration

In order to supply oxygen to and remove carbon dioxide from their tissues,
animals must exchange these gases with the environment

Two features are common to all respiratory systems

First, they almost always have structures that ____________________________
the amount of surface area in contact with air or water

Second, they have some way of keeping the gas exchange surfaces
______________________ so that diffusion can occur

Some animals that live in water or in very moist soil, such as cnidarians and
flatworms, respire through their ___________________

Aquatic organisms – mollusks, crustaceans, some insects, and many annelids, for
example – have gills that help them exchange gases with the water around them

Terrestrial invertebrates have evolved several organs for breathing air

These include the highly modified __________________________________ of
land snails, the ____________________________ of spiders, and the
_________________________________ of insects
Excretion

Multicellular animals, whether they live in water or on land, must control the
amount of water in their tissues

At the same time, all animals must get rid of toxic nitrogenous wastes produced as
a result of cellular metabolism

_____________________________________ in invertebrates have evolved in
ways that enable these animals to both regulate the amount of water in the body
and get rid of nitrogenous wastes

In all animals, the breakdown of amino acids during cellular metabolism produces
_________________________

Many aquatic animals simply allow ammonia to diffuse through their body tissues
and out into the surrounding water, which immediately dilutes it and carries it
away

Terrestrial animals must do two things: conserve body water and get rid of
nitrogenous wastes at the same time

In order to do this, many invertebrates convert ammonia into ________________

Urea is soluble in water and is much less toxic than ammonia

The waste product produced by the excretory system, which is called
_______________________, is expelled from the body

Terrestrial animals can get rid of more wastes in less water than their aquatic
counterparts

Sponges, cnidarians, and roundworms
o _________________________ through body surfaces

Freshwater flatworms
o ____________________________

Insects and some arachnids
o ___________________________________

Annelids, mollusks, and chordates
o _____________________________
Response

___________________________________ gather information from the
environment, process information, and allow animals to respond to it

Invertebrates show three obvious trends in the evolution of the nervous system:
centralization, cephalization, and specialization

Cnidarians and some flatworms
o _______________________

Other flatworms
o _______________________

Mollusks and arthropods
o Ganglia are organized into a _________________
Reproduction and Development

Many simple invertebrates reproduce __________________________ through
fragmentation or budding

Asexual reproduction allows animals to produce offspring rapidly from a single
individual

____________________________________ maintains genetic diversity in a
population

Although sexual reproduction does not create new genes, it does result in new
____________________________________________

Most of the more complex animals reproduce __________________________
Fertilization

There are two basic ways in which sperm cells and egg cells are brought together
in sexual reproduction: __________________________________________ and
__________________________________________

External fertilization is generally associated with less complex animals

The eggs are fertilized ________________________ the body

Internal fertilization is associated with more complex animals

The egg is fertilized ___________________ the female’s body
Parental Care

Many ________________________________ do not take care of their fertilized
eggs or young

The eggs are _______________________ as soon as they are laid

Most of the young are eaten or are exposed to adverse environmental conditions
and die

Some invertebrates take care of their offspring

Some of the ways in which invertebrates care for their offspring may seem
horrifying to humans

For example, the eggs of some species of mites hatch within the female’s body

The larvae immediately begin to devour their mother from the inside!

Within two days – while still inside their mother’s nearly empty exoskeleton – the
young mites mature, mate, and eat their way to the outside

The males die within a few hours

The females seek out prey in the form of insect eggs and begin to feed – even as
their own offspring start chewing on their internal organs