Very valuable Animal Notes

 

Basic Structure of an animal

The basic difference between an animal and a plant is that instead of being an autotroph they are heterotrophs. An animal can best be described as “ a multicellular, heterotrophic, and usually motile organism”. The difference between unicellular and multicellular animals is that multicellular organism have tissues which allow for the division of labour done by cells.

 

Inverterbrates

Basically, any animal (multicellular) without a backbone is an invertebrate. Invertebrates can live in aquatic, terrestrial and parasitic environments. They may range in size from the microscopic to mammoth squid.

 

• And now a word from our sponsor… ( boy these would be great short answer questions…

 

Some benefits of inverterbrates…(five)

• They provide habitat for other animals
• Habit allows food for other animals to eat
• Worms dig up and turn over soil, allowing plants to grow
• Many mollusks are food…even snails..yum!
• Insects pollenate plants

 

But…

Many invertebrates can cause disease (five)

• Trichinella causes infection due to eating uncooked meat
• Tape worms infect domestic and undomestic species
• Insects and mollusk can be vectors for parasitic worms

Oiwee..

• Insects and cnidarian can sting…if you get in their space
• And octupi and squids can bite!

 

Germ Layers

Importance of having three germ layers, is that each layer allows for cell specialization. With the formation oftissues, these germ layers can specialize to preform specific tasks. As the organism evolve, one notes an increase in functions of each germ layer.

 

For example

• Ecoderm tissue can diversify to form structural support, defensive stinging cells, specialized hooks or become dense cutticle to limit being digested.

 

• Mesoderm tissue can diversity to form muscle tissue and reproductive tissue

 

• Endoderm tissue can diversify to form digestive tissue

 

Symetry

Symetry and life style

Animals that tend to stay in one place will show no symetry (such as coral) or radial symetry such as sea anemome. Since these organisms live in one spot, they depend upon the flow of water to both provide food and distribute gametes. With the advent of movement, animals will shift to bilateral symetry. This means that they can hunt for food and muscles will be innervated by a nerve tissue.

 

Development of systems

Linked to coelom

The basic distinction of an animal is to eat, so tissues will be developed to eat food. If you have a simple surface area to volume ratio, there is no need to create systems for digestion. For example tape worms can absorb food across a simple single cell layer. Acoelomates tend to show simple strategies for digestion, such as filter feeding, or parasitic absorption. The planarian does have a simple gut that also doubles to move food in and out of the body. With the increase in locomotion there is a need for more food. The formation of a full digestive tract, such as pseudocoelomate nematod worms, allows for food to go in and out of the body by two pores. In addition, muscle movement within the body can work independently of external muscle. Please check previous notes for more facts about the coelom. With more food there is more waste, so there is development of excretory system.

 

Filter feeding

Specialized cells to create current (collar cells)

Specialised cells to form pores

Less energy used to find food

 

Internal and external digestion

External

Simple guts to tubular guts

Digestive enzymes to rapidly disolve food prior to being absorbed by

Cells

 

 

Parasitism

Adaptions

Hooks and suckers

Cutticle

Proglottids

No need for digestive system

 

Classification:

 

Porifera

Sample : Sponges

These are asymetric, filter feeding critters that almost look like rocks! In fact the ones at the aquarium are! These animals have three layers, although they are made from two germ layers. So sponges do have distinct cell types. The middle layer is made of spicules which form a skeletal system that protects and shapes the organism. The spicules are made of calcium carbonate which is hard enough to make…rock..or fossils. Water is filter in through pore by collar cells. These cells use flagella to produce water current and gametes. Sponges reproduce asexually by budding. Since these animals are sedentary they depend upon the flow of ocean currents for food. Though this may be hazardous if the water is not pure, they do not have to expend a lot of energy to get food.

 

Cnidaria

Sample: Hydra, Jelly fish, Sea Anenome

These animals are radial in symetry. They eat by stinging their prey with nematocyst which in the case of the hydra can paralyze the prey. The interesting thing is that these same tentacles can also be used for fertilization, as in the jelly fish. Cnidarian some times have moving and sendentary stages. They usually have tentacles souronding a mouth. Organism such as the jelly fish can have both sexual and asexual forms.

 

Platyhelminthes

Sample: Planaria , Flukes and tapeworms

Flat worms can either be free living or parasitic. They show bilateral symetry and unique loss or gain of systems. Free living species show nerve tissue development with anterior ganglia and nerve cords. Planaria have both eyespots and sensory lobes. In comparison, parasitic form tend to show anterior specialization to adhere to the host, such as suckers or hooks. Free swimming Planaria show unique regenerative properties. Parasitic species such at tapeworms no longer need digestive tissue due to the environment they live in. However, to insure survival, they have mass producing proglottids. These segments have both male and female tissue to increase the rate and amount of eggs. Proglottids develop along the length of tape worm, with the mature ones being at the posterior end (which contain many eggs) and the immature ones being close to the scolex. Another type of parasitic worm are flukes such as the liver fluke. This parasite has a life cycle that start within the host stomach, moves to the intestines, then the liver and then the gall bladder…so the parasite not only moves around outside the host, it also moves within the host!

 

Round worms.

Samples: nematoda, hookworm, filarian worm,ascaris and trichinella

We now enter the world of psuedocoelomates. Round worms can be free living or parasitic. They have complete digestive tracts with a mouth and an anus. Parasitic worms can specialize ectoderm tissue to form cutticle which prevents them from being digested. One of the most graphic round worm infections is elephantiasis, which is due to filarian worms. This parasite is associated with lymph vessel blockage which causes the body to swell to…elephant proportions! The medical staff and worm symbol can be traced back to how this worm was once extracted from the skin by wrapping it around a stick. Life cycle of ascaris enters the body via the gut but eventually works its way to the lungs, via the blood to the liver to the heart. Each time the host coughs they reinfect themselves. To infect other hosts the eggs are excreted by adult worms in the gut. If the eggs and the adult are remain in one host, the spreading of the parasite is limited.

 

Some Vocabulary

Term	Definition or example
Coelom
Budding
Medusa
Hermaphrodite
Echinodermata
Gastropoda
Nematocysts
Collar cells
Flame cells
Cutticle
Polyp
Vector
peritoneum
tentacles

 

 

 

 

 

Now using the text and notes, try and answer the following

 

Big ideas in biology

Interactions

• What are some examples of animal interactions?
• How are coral and sea anenome associated with marine ecology?
• How is symetry related to lifestyle?
• What are some advantages of living in a marine environment?
• What are five ways inverterbrates are helpful to humans?
• What are five ways invertebrates are harmful?
• What is a parasitic life cycle and how can it change?

 

Changes with time

• What changes in structure occur as animals switch from marine to land?
• How do sedentary animals such as coral and hydra deal with reproduction?
• How would adapting to a parasitic lifestyle be advantageous?

 

Structure and function

• What unique structures do parasitic tape worms have? ( 3 )

What are the unique structures for:

Sponge

• Sea anemome
• Hydra
• Planaria
• Parasitic flukes and flatworms
• Nematoda worms

 

 

 

 

 

 

And now for a great short answer question…and final study tips

 

Now if you found a critter on the beach…how would you classify them? How could you decide what group of organisms you critter belonged to?How does your critter move?

What unique structures does it show?

How does it respond to a stimuli?

What structures does it show that may show if it is a predator or prey?

Does it have protective layers or structures?

How do you suppose it maintains water balance?

What sort of digestive system does it have?

Does it have massive gonads…no it is not a bull dog!

So from these facts…

What is your mystery critter…

See it pays to learn the general properties of …

• A coral
• A cnidarian
• A free swimming platyhelminthes
• A parasitic worm

 

 

Study tricks…Importance of the number three

 

Three germ layers

Ecto

Endo

Meso

 

Three developments of coelom

Acoelomate

Psuedocoelomate

coelomate

 

Three advantages of a coelom

 

Three pattern of feeding

Filter

Free living, with external digestion

Parasitic