ZEBRA MUSSEL

The zebra mussel is a species of small freshwater mussel, an aquatic bivalve mollusc. This species was originally from the regions of the  Black, Aral and Caspian seas but it has been accidentally introduced in many other areas as the Ebro River, and has become and invasive specie.

The zebra mussel has a triangular shape and in their shell it has dark grey and black stripes. It could be 5cm long but usually it is 3cm, and it could live 5 years. They live grabbed in the soil thanks to some “strings” (byssal threads) so it is very difficult to remove them. They grab in the rocks of the rivers, in pipes (collapsing them, so they have to be changed more frequently and more money is spent), boats and on the shells of other animals, not allowing them breath and eat, so they die. The zebra mussels filter the water so as it has less particles more light pass trough it, making plats grow and, as they need oxygen, less oxygen can be taken from fish so they also die.

The zebra mussel is an alloctone species in Aragon and it is changing the plants and animals of these rivers, and also the relationships between the humans and the nature because we have taken it here, and because it will be our job to take it out.

The cycle of cebra mussel's life

This is the cycle of the life of the zebra mussel

The characteristical stripes of the shell of the zebra mussles.

How the zebra mussels grab anywhere they can.

I like this web page because it has information about a lot of different topics and it is very well explined. It also has things about ecology and ecosystems.

HERE 😉

CONTRASTING LAMARCK AND DARWIN

In the video of the professor George Wolfe, he explained the difference between the theory of evolution of Lamarck and the Darwin’s one. Ha said that the biologists usually asked themselves why there are changes in the organisms instead of just asking what a change is.

Lamarck had two tenets (principios) for evolution:

use and disuse

the inheritance of acquire characteristics.

That means that if an organism didn’t use an organ it will disappear by time or of they used a lot an organ, or needed better characteristics they would grow or change for better little by little, if one giraffe need a longer neck, it will stretch it until it grows a little and that difference will pass to their offspring that will stretch their necks to grow them more, until they have the perfect longitude.

Darwin had another idea which had some steps:

1-overpopulation: first there were a lot of animal of the same specie.

2-variation: some of those animals, that will be for example giraffes, will have a longer neck, as some of us have a long nose, or curly hair.

3-compete: as there were a los of animals, they compete for survival, for example for food and the giraffes with the longer necks will have easier to take the leaves of the higher trees.

4-survival of fittest: the best animals, in this case the giraffes with the longer neck, will have better possibilities to survive as they can take more food, so giraffes with long necks will be fittest.

5-reproduction: as giraffes with a long neck are the fittest they will have more possibilities to reproduce and have offspring, because females choose the best ones for breeding. Then their characteristic will be passed to offspring and finally most of the giraffes will have long necks.

But this don’t happens because giraffes think they need a long neck and they try to stretch it, it just happens because they are lucky and they have a characteristic that will be better, as it could have been worse for them. That is the difference between Lamarck’s and Darwin’s theories, the first happens because they need it, and the second just randomly and through genes.

Finally George Wolfe asked a question about what will Lamarck think about the brains of woodpeckers and their protection to the hits in the trees, and what will think Darwin.

🙂

THE SLOTH

The sloth is a mammal that lives in the jungles of South America.

Their principal characteristic is that they move very slowly and they sleep more than 16 hours a day.


They are adapted to the environment with some physical features:

–       As they don’t obtain enough energy from the leaves they eat they accumulate solar energy. In the day their body reaches 35 degrees centigrade and at night it keeps at 25 degrees.

–       Their hairs are insulated so water doesn’t wet them.

–       They have very long claws (5-8cm) to climb trees easier and not to fall n the ground where jaguars could trap them because they move very slowly.

–       They have algae growing in their hair that make them green to camouflage from predators.

–       Thanks to their neck they could turn the head until 270º so they could see without moving very much.

–       Their forelegs have double length than the others because when they hang they grab with them.

–       Their outer hairs grow in a direction opposite form that of mammals, from the belly to the back because they are all day hanged so the rain water doesn’t wet them and don’t lose much hot.


And they are so famous because of their films 🙂


NATURAL SELECTION IN SLOTH

Firstly every sloth had the hairs growing as in all mammals, from the back to the belly, but as they were all days hanged in the branches, when it was raining they lost their heat because the became wet, as the water could enter the layer of hairs. Sloth doesn’t take enough energy from the leaves they eat so they sunbathe to warm their bodies without wasting energy. When the sloths lost their heat because of their hairs, they had to pass more time sunbathing and more of them were caught by eagles.

Then some of them started having an adaptation, theirs hairs grew in the opposite direction: from the belly to the back and then they didn’t lose so much heat and didn’t have to sunbathe too, so less of them died in the struggle of existence, and as only the fittest survive, the number of “new” sloths increase.

They started reproducing and as that characteristic was an advantageous one the traits passed to their descendants and it became a variation that made sloths better to survive.

I think i can now post a link, an di undesrtand what the teacher had said.
http://www.nationmaster.com/encyclopedia

when i was looking for information about codominance I found this interesting enclycopedia were the information was very good explained, and as we have to add a link i put it but i don’t know if i made it well :S

Today, in the lesson the teacher asked a question about Mendel. Why did he use PEAS instead of other plant or even animals?

Gregor Mendel used pea pod plants for different reasons:

Pea plant are easy to use, and they grow fast so you don’t have to wait a lot of time to see the plants in their maturity, and you can make more generations.

-Each pea in the pod (the vessel that contains the seeds of a plant) is an offspring, which means a lot of offspring’s in each plant.

– You can cross or self-pollination them, by yourself so you can have more control over the plants. If he had chosen animals he could not self-reproduce them, and they had more traits that will difficult it.