Contemporary Animal ScienceUnit 1

History of animals

The oldest direct traces of life on earth date back 3.4 – 3.5 billion years .

Rocks in Australia and Southern Africa have shown fossilized remains of blue-green algae.

The first land plants were believed to have been established about 420 million years ago

A long time ago…

• 2.2 billion years ago free oxygen was present in the atmosphere. Living things used this reactive substance, not decaying plant material, in biochemical functions of their cells. The free oxygen in the atmosphere also produced a layer of ozone, which filters out the UV light from the sun that is harmful to life.

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OH.. plants were first…

The first land plants were believed to have become established about 420 millions yrs ago

This is also the period of time when invertebrates, like arthropods and worms appeared on land.

They fed on the decaying plant material.

Vertebrate animals, in the form of amphibians and reptiles, appeared about 370 million years ago

180 million years ago, dinosaurs appeared along with mammal like reptiles.

The first birds and mammals appeared 135 million years ago during the Jurassic period (when dinosaurs became abundant).

135 – 70 million years ago, dinosaurs and marine reptiles reached their period of greatest abundance and then disappeared. Why?

With the extinction of dinosaurs, opportunity arose for smaller creatures to evolve and become abundant.

70 – 40 million years ago, placental mammals (mammals having a placenta with the embryo and fetus are nourished in the uterus) evolved, dispersed and adapted to new environments.

Most small mammals are placental mammals.

Have a vascular organ that unites the fetus to the uterus. This is how the fetus received nourishment.

Domestication of Animals

• Not sure how it started but believed when human hunters brought back the young of the adult animals they killed.

• Dogs are believed to be the first animals domesticated

• Wolves may have hung around villages looking for meals, and the cubs were probably domesticated and became companion animals

• They also warned villagers of pending danger• The discovery of a dogs jawbone found in a cave in

Iraq dates back 12,000 years. This is the earliest indication of a domesticated animal.

Cats interaction with humans date back about 3500 years ago

The domestic cat probably provided pleasure, companionship and controlled rats and mice.

Small animal industry

• Pet ownership is at an all time high 57.9 % of all American families (54.8 million households include at least one companion animal.

• Cats outnumber dogs as the most common household pet.

• Over 57 million cats in the U.S. compared to 52.2 million dogs.

• Dogs are found in 36.5 % of the nations household and cats in 30.9 %

• Most cat owners have an average of 2 cats.

Other Pets?

American households also have

11.7 million birds

24 million fish

4.6 million rabbits

1.3 million hamsters

Pet food produces 6.5 billion in sales

Vet bills are nearly 4.6 billion for dogs, 2.3 billion for cats and 185 million for birds.

Classification of organisms

Taxonomy – the science that is concerned with the naming and classification of organisms

Aristotle is credited with the first attempts of classifying organisms based on their structural similarities.

Linnaeus, a Swedish Botanist, is credited with developing our modern method of classification.

7 Taxa

Kingdom

Phylum

Class

Order

Family

Genus

Species

5 Kingdoms

• All organisms are divided into five kingdoms1. Monera – Bacterial organisms with no true

nucleus and reproduce by fission2. Protista – single celled or microscopic animals

(algae)3. Plantae – multi-cellular photosynthesizing

organisms, higher plants and multi-cellular algae

4. Fungi – molds, yeasts and fungi5. Animalia – vertebrates and invertebrated

All animals that we will talk about belong to the phylum Chordata

Chordata – 4 Characteristics

• 1. An embryonic notocord which is usually replaced by the spinal cord

• (notocord – a flexible cord of cells in the embryo stage of growth that eventually becomes the vertebra)

• Dorsal tubular nerve cord running down the backside

• Pharyngeal or throat area gill slits (the area of the pharynx)

• A rear tail area

Chordata…

Although they posses these structures at some embryonic stage, these characteristics may be altered or disappear in later stages of life.

4 Classes of animals

1. Mammalia– Vertebrates that posses mammary glands, have

a body that is more or less covered with hair, and possess a well developed brain

 2. Reptilia– Snakes, lizards and turtles– Cold blooded vertebrates having lungs, and

entirely bony skeleton, body covered with scales or bony plates and a heart with 2 atria and a single ventricle

3.Aves– Warm blooded vertebrates animals with 2 legs,

wings, feather and which lay eggs.– Birds

4. Osteichthyes– Large group of vertebrate animals that live in

the water and have permanent gils for breathing, fins and body usually covered with scales

• Fish

This system of naming species is called binomial nomenclature and used the Latin language. Each species has a name composed of 2 words. The first word is the genus and is written with the first letter capitalized. The second name is the species and is written with a lower case first letter

In some cases an organism may have a subspecies name and would then use a trinominal nomenclature.

Domestic dog

• 1. Kingdom – animalia – animal kindom• 2. Phylum – Chordata – animals with vertebrae• 3. Class – mammalia – animals that suckle

young• 4. Order – Carnivora – flesh eaters• 5. Family – canidae – the dog family • 6. genus – Canis – dog• 7. Species – Familiaria – domestic dog