Thursday, January 6, 2011

invertebrates


There are two basic groups of higher animals. They are vertebrates and invertebrates. While both have advanced through the processes of evolution, there is one fundamental difference. Invertebrates do not have backbones. Both groups are in the Kingdom Animalia, but their bodies are organized differently. What makes invertebrates different? All invertebrates share common traits. At the bottom of the invertebrate world are the sponges. Sometimes they don't fit in but they are still part of the group. Here's the nice and neat little list.



(1) They are multicellular. It's more than being a colony of individual cells. The cells are working together for the survival of the organism. All of the cells have specific duties and responsibilities. 


(2) No backbone. We already talked about this one. That's the whole definition of invertebrate, no vertebrae. 


(3) No cell walls. When we talked about plants, we always mentioned cell walls. Invertebrates don't have them. Remember that even if none of them look like animals, they are. Being an animal means you have no cell wall. 


(4) Here are a few that have the qualifier "most" attached. That means not all of them have the trait, but most do. Most of them have tissues (not sponges) that are specific organizations of cells. Most of them reproduce sexually (not asexually). That means two gametes combine to form a new organism. Those gametes come from separate organisms (male and female). 

Most invertebrates can move. Even sponges move when they are very young and very small. Once they settle down they don't move anymore. Other invertebrates like lobsters and insects move around their whole lives. Most invertebrates are organized in a way called symmetrical. Symmetrical organization means when you can draw a line down the middle of the organism and the two sides look like mirror images. Draw a line down the middle of yourself and one side looks like the other side. If you draw a line down the middle of an octopus you would find two sides with equal parts. Remember we said most? Sponges and some coral are not symmetrical. 


(5) Invertebrates can't make their own food. Scientists use the word heterotrophic. Heterotrophs feed off other things to get their energy. Plants are autotrophic. They make their own food. Being heterotrophic is one of the main characteristics of being an animal. We eat things, whether it is plants or other animals. That's just the way the world works. 

Protozoa
Protozoa are simple, single-celled animals. They are the smallest of all animals. Most protozoa are microscopic in size, and can only be seen under a microscope. However, they do breathe, move and reproduce like multi-celled animals.

There are several types of protozoa. The amoebas are clear, shapeless cells. Flagellates have a body shape looking like a hair.
Although we can't see them, protozoa do a lot for us. Protozoa play a useful role in the food chain as a source of food for fish and other animals. Some protozoa are helpful to humans by eating dangerous bacteria. Unfortunately, other protozoa are parasites and can be harmful to humans by transmitting disease.
Protozoa eat tiny algae and bacteria. Some protozoa absorb food through their cell membrane. Others surround and engulf their food or have openings to collect food. They digest their food in stomach-like compartments called vacuoles.
Protozoa take in oxygen and give off carbon dioxide through the cell membrane.
Protozoa reproduces by splitting in half.


Annelids
There are about 9,000 species of Annelids known today, including worms and leeches. They can be found almost anywhere in the world. Annelids have existed on Earth for over 120 million years.

Annelids have bodies that are divided into segments. They have very well-developed internal organs. One common characteristic of annelids is that they don't have any limbs.
Some annelids may have long bristles. Others have shorter bristles and seem smooth, like the earthworm.
There are many types of worms. Commonly known worms include earthworms, roundworms and flatworms. Most worms are small, measuring fractions of an inch to several inches long. Other worms, such as the ribbon worm, can grow up to 100 feet in length. Some worms are considered parasites, in that they live inside the human body.


Mollusks
Mollusks were among the first inhabitants of the Earth. Fossils of mollusks have been found in rocks and date back over 500 million years. Mollusk fossils are usually well preserved because of their hard shell.
Most mollusks have a soft, skin-like organ covered with a hard outside shell. Some mollusks live on land, such as the snail and slug. Other mollusks live in water, such as the oyster, mussel, clam, squid and octopus.
Land living mollusks, like the snail, move slowly on a flat sole called a foot.
Ocean living mollusks move or swim by jet propulsion. They propel themselves by ejecting water from their body. For example, the squid ejects water from a cavity within its body, and the scallop ejects water to move by clamping its shell closed.
Other ocean living mollusks, like the oyster, attach themselves to rocks or other surfaces, and can't move. They feed by filtering small food particles from water that flows through them.


Echinoderms
Echinoderms are marine animals that live in the ocean. Common echinoderms include the sea star, sea urchin, sand dollar and sea cucumber. Most echinoderms have arms or spines that radiate from the center of their body. The central body contains their organs, and their mouth for feeding.
Sea stars, commonly known as the starfish, have 5 or more arms attached to their body.
On the bottom of the Starfish are small tube feet to help with movement and feeding. The starfish's mouth is underneath, and is capable of eating other sea life such as clams and mussels.
Another type of echinoderm is the sea urchin. Sea urchins have many spines connected to their body. These spines help to protect them from predators.

Crustaceans
Crustaceans are a type of Arthropod. The name may not sound familiar, but you probably know them. You may even have eaten one.
Crustaceans live mostly in the ocean or other waters. Most commonly known crustaceans are the crab, lobster and barnacle.
Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system.
The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating.


Arachnids
Arachnids are a type of arthropod. You know many of them as spiders. Common arachnids are spiders, scorpions, ticks and mites.
Like other arthropods, the arachnids have a hard exoskeleton and jointed appendages for walking. Most arachnids have 4 pairs of legs. In some, the first pair of legs may be used for holding their prey and feeding. Unlike other arthropods, arachnids do not have antennae.
Spiders are easily recognized with their 8 legs. All legs are used for walking. The first pair of legs is also used for holding prey and feeding. The second pair of legs may also be used for holding and killing their prey. Most spiders have 8 eyes. Spiders have fangs that are used to inject poison to paralyze or kill their prey. Many spiders can produce silk threads to spin webs for catching prey, and for building an egg sack to hold and protect their eggs.
Scorpions are large arachnids, some reaching over 8 inches in length. They have 4 pairs of legs, and a pair of pincers for catching and holding their prey. Scorpions also have a sharp stinger at the end of their tail that is used to paralyze or kill insects and small animals.
Mites and ticks are small arachnids that are parasites living on the blood and tissue fluid of other animals. They can occasionally transmit disease.


Insects
The insect's head has a pair of antennae, and a pair of compound eyes. Compound eyes are different from human eyes which have a single lens for each eye. Compound eyes have many lenses for each eye. For example, the fly has about 4,000 lenses in a single eye. This provides them with very good eyesight.
The thorax contains the legs for walking, swimming, jumping or digging. The thorax may also have wings for flying. The abdomen contains many body organs, such as the heart, respiratory system, digestive system and reproductive system.
The insect's hard, exoskeleton makes it difficult for the insect to grow and get larger. This is because the exoskeleton can't grow and get larger. Many insects must molt in order to grow. Molting is the process where an insect sheds it outer skeleton. It wriggles out of this old skin, and a new, larger exoskeleton develops.
Sources
http://www.biology4kids.com/files/invert_main.html
http://www.kidport.com/reflib/science/animals/animalindexinv.htm
http://www.kidport.com/reflib/science/animals/Protozoa.htm
http://www.kidport.com/reflib/science/animals/Annelids.htm
http://www.kidport.com/reflib/science/animals/Mollusks.htm
http://www.kidport.com/reflib/science/animals/Echinoderms.htm
http://www.kidport.com/reflib/science/animals/Crustaceans.htm
http://www.kidport.com/reflib/science/animals/Arachnids.htm
http://www.kidport.com/reflib/science/animals/Insects.htm
Good site to visit 
http://animals.nationalgeographic.com/animals/invertebrates/


done by: Aaron, Imran, Norman, and Eugene
















13 comments:

  1. I have learnt that sponges move when they are very young and very small. Once they settle down they don't move anymore.
    I have discovered that Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans.

    ReplyDelete
  2. I have learnt that...Invertebrates are multicellular. Typical of animals, all of the cells have specific duties and responsibilities that ensure the survival of the organism. They do not have backbone, and that is the main characteristics that is different from vertebrates and invertebrates. They do not have cell walls. Most of invertebrates have tissues, with the exception of sponges, that are specific organizations of cells. Most of them reproduce sexually. Most invertebrates can move. Invertebrates do not have chlorophyll present in them, so they cannot make their own food.

    I have discovered that...Due to their lack of complex skeletal system, invertebrates also tend to be smaller and slow moving in nature, with some exceptions. The Giant squid can reach speeds of 55 kilometers per hour. Their lack of backbones and complex nervous systems make it very difficult for invertebrates to be adaptive to multiple environments as well.

    ReplyDelete
  3. I learnt that invertebrates are multicellular. Insects have compound eyes which are different from human eyes which have a single lens for each eye.Arachnids are a type of arthropod which are spiders.

    I discovered that at the bottom of the invertebrate world are the sponges which is unexpected.There are about 9,000 species of Annelids known today, including worms and leeches and can be found almost anywhere in the world. They have also existed on Earth for over 120 million years.

    ReplyDelete
  4. 1 thing i learned is that arachnids consists of scorpions and spiders. Like other arthropods, the arachnids have a hard exoskeleton and jointed appendages for walking.

    1 thing i discovered is that the word arachnid came from Greek mythology.

    ReplyDelete
  5. I have learnt that...
    There are 7 types of invertebraes.

    I have discovered that...
    All vertebraes have a similar basic shape - they have a backbone across the length/height of the animal, where the mouth is near the front and the anus is near the end of the backbone.

    ReplyDelete
  6. I have learnt that...
    Most invertebrates are organized in a way called symmetrical and that most of invertebrates have tissues, with the exception of sponges.

    I have discovered that...
    The group includes 95% of all animal species.

    ReplyDelete
  7. I have learnt that most invertebrates can move and that sponges move when they were young and small and will stop moving when they settle down.

    I have discovered that Protozoa move around with whip-like tails called flagella.

    ReplyDelete
  8. I have learned that worms and leeches belong to a group called Annelids which have existed on Earth for over 120 million years. They have bodies that are divided into segments and have very well-developed internal organs.

    I have discovered that starfish have the ability to grow back an arm if it is cut off. The severed arm can even grow into a new starfish.

    ReplyDelete
  9. I have learnt that Annelids have bodies that are divided into segments, very well-developed internal organs and they don't have any limbs. Some annelids may have long bristles. Others have shorter bristles and seem smooth, like the earthworm.

    I have discovered that many invertebrates have a fluid-filled, hydrostatic skeleton.

    ReplyDelete
  10. i have learnt that all invertebrate are multicellular organism.

    i have discovered that the group covered most of the animal species

    ReplyDelete
  11. I've learnt that..
    Invertebrates: They are multicellular organisms
    Protozoa: They are simple, single-celled animals.
    Annelids: They have bodies that are divided into segments.
    Mollusks: They were among the first inhabitants of the Earth.
    Echinoderms: They are marine animals that live in the ocean.
    Crustaceans: They live mostly in the ocean or other waters.
    Arachnids: They do not have antennae.
    Insects: They have compound eyes which have many lenses for each eye

    I've discovered that..
    The group includes 95% of all animal species.
    Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans.

    ReplyDelete
  12. I have learnt the key characteristics of the 7 types of invertebrates.

    I have discovered that there are actually 7 types of invertebrates.I thought they were already classified as a group "Invertebrates".

    Questions:
    You said invertebrates was mutilcellular but on the first type of invertebrates :Protozoa,you said it was a single cell organism.

    Can you include some pictures of videos.Looks wordy~

    ReplyDelete
  13. I have learnt that most invertebrates are symmetrical.

    I have a question to ask, however. If amoebas are invertebrates, then are they under the kingdom Prostita too?

    I have discovered that protazoa feed by pulling another cell into its 'mouth'

    ReplyDelete