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By the end of this section, you will be able to:
  • List the features that distinguish the animal kingdom from other kingdoms
  • Explain the processes of animal reproduction and embryonic development
  • Describe the hierarchy of basic animal classification
  • Compare and contrast the embryonic development of protostomes and deuterostomes

Even though members of the animal kingdom are incredibly diverse, animals share common features that distinguish them from organisms in other kingdoms. All animals are eukaryotic, multicellular organisms, and almost all animals have specialized tissues. Most animals are motile, at least during certain life stages. Animals require a source of food to grow and develop. All animals are heterotrophic, ingesting living or dead organic matter. This form of obtaining energy distinguishes them from autotrophic organisms, such as most plants, which make their own nutrients through photosynthesis and from fungi that digest their food externally. Animals may be carnivores, herbivores, omnivores, or parasites ( [link] ). Most animals reproduce sexually: The offspring pass through a series of developmental stages that establish a determined body plan, unlike plants, for example, in which the exact shape of the body is indeterminate. The body plan    refers to the shape of an animal.

Part a shows a bear with a large fish in its mouth. Part b shows a heart in a jar. Long, threadlike worms extend from the heart.
All animals that derive energy from food are heterotrophs. The (a) black bear is an omnivore, eating both plants and animals. The (b) heartworm Dirofilaria immitis is a parasite that derives energy from its hosts. It spends its larval stage in mosquitos and its adult stage infesting the hearts of dogs and other mammals, as shown here. (credit a: modification of work by USDA Forest Service; credit b: modification of work by Clyde Robinson)

Complex tissue structure

A hallmark trait of animals is specialized structures that are differentiated to perform unique functions. As multicellular organisms, most animals develop specialized cells that group together into tissues with specialized functions. A tissue is a collection of similar cells that had a common embryonic origin. There are four main types of animal tissues: nervous, muscle, connective, and epithelial. Nervous tissue contains neurons, or nerve cells, which transmit nerve impulses. Muscle tissue contracts to cause all types of body movement from locomotion of the organism to movements within the body itself. Animals also have specialized connective tissues that provide many functions, including transport and structural support. Examples of connective tissues include blood and bone. Connective tissue is comprised of cells separated by extracellular material made of organic and inorganic materials, such as the protein and mineral deposits of bone. Epithelial tissue covers the internal and external surfaces of organs inside the animal body and the external surface of the body of the organism.

Concept in action

View this video to watch a presentation by biologist E.O. Wilson on the importance of animal diversity.

Animal reproduction and development

Most animals have diploid body (somatic) cells and a small number of haploid reproductive (gamete) cells produced through meiosis. Some exceptions exist: For example, in bees, wasps, and ants, the male is haploid because it develops from an unfertilized egg. Most animals undergo sexual reproduction, while many also have mechanisms of asexual reproduction.

Questions & Answers

different between demand and supply
Francis Reply
what is the demand and supply of Qd=40,000-6P Qs=14P-28,000 the equilibrium price
Rocky Reply
3400
Ram
what is economics by Adams smith
Diana Reply
economics by Adams Smith's
Francis
to earn wealth more and more
Ram
what are the poor performance of the monopolies
Thandolwethu Reply
it controls only price or production not both a same time
Ram
Difference between demand and supply
Kareem Reply
demand talks about the consumers and supply also talks about producers
Bright
demand talks about the relationship between price and the quantity demanded for a certain goods and supply talks about the relationship between price and quantity supply of a certain goods .
Mutala
demand show the quality demanded at different price n time whereas supply show the quality ready to sell in market by seller at different price n time.
Ram
describe the issue gain from trade will improve economic growth and living standard.
Allison Reply
discribe gain from trade will improve economic growth and living standard
Allison
discribe gain from trade will improve economic growth and living standard
Allison
what is the outcome of exchange rate?
Allison
gain from international trade to a country which import are elastic n export are inelastic
Ram
what is utility
Roberta Reply
the capacity of a good to satisfy our want.
Ram
what is the relationship between the elasticity of demand and total revenue
Atedago Reply
I don't know
Taofeek
negative. but for unit elasticity of demand, the relationship doesn't exist between them.
Ali
what is income elasticity of demand
Esther Reply
income elasticity of demand measure the degree of responsiveness of demand for a commodity to a small change in the income of the consumer
Atedago
monopolistic competition has all except which of the following basic characteristics?
Sharon Reply
what are the Features of money
Abubakarr Reply
how to calculate the elasticity of supply?
Asnaira Reply
PES=Qs2-Qs1/Qs1÷P2-P1/P1
Soko
why is economics important
Gifted Reply
why is it important
Gifted Reply
for what?
Vicky
economics
Gifted
what is demand
Mutala Reply
Demand Is Anything that A Customer are willing and able to buy at different price level.
Basit
what demand schedule
Mutala
demand schedule is a tabular representation of different quantities of commodities that consumers are willing to purchase at a specific price and time while other factors are constant.
MEOW
A full account of the demand, or perhaps we can say, the state of demand for any goods in a given market at a given time should state what the volume (weekly) of sales would be at each of a series of prices. Such an account, taking the form of a tabular statement, is known as a demand schedule.
MEOW
State the type of elasticity of demand
Emmanuel
price elasticity of demand . and it refers to the degree of responsiveness of change in quantity demanded for a commodity to a change in price if the commodity itself
Mutala
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Source:  OpenStax, Natural history supplemental. OpenStax CNX. Aug 19, 2014 Download for free at http://legacy.cnx.org/content/col11695/1.1
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