Question

how do you think microscopic animals can survive without a circulatory system?

Answer 1

just the same way as they reproduce with a reproductive system and take nutrition without a digestive system...!!!! :)

Answer 2

you won't talk about the haemcoel?

Answer 3

i guess a single cell doesn't have enough space to accomodate "systems" so everything is done in a very simple, rudimentary way...

haemocoel is just a cavity, not a real system as such.....

Answer 4

hey friend, if u find the answers satisfactory, pls click GOOD ANSWER button to show appreciation... :})

Answer 5

I have never heard of a microscopic animal. There are organisms....

Answer 6

Harkirat am not quite satisfied
mkw93 thats what the question says

Answer 7

what more do u need???

Answer 8

i dono i just feel am not satisfied

Answer 9

See in a single -celled organisms, there is no real need of "circulating" anything. The food is digested within the single cell itself and all the nutrients derived are already inside the cell and are thus assimilated easily.

In multicellular organisms like humans, it it difficult for each cell to catch and digest its own food. Hence their is a separate system which derives the nutrition from the food. Now this nutrition has to be sent to all cells and hence a circulatory system is required.

Similarly for respiration a single-cell organism can easily get oxygen but for humans oxygen has to be distributed and hence again a circulatory system is required.

Answer 10

what does circulation have to do with food?

Answer 11

The whole purpose of the circulatory system is to distribute the nutrients derived from food to all cells of the multicellular organism !!!!!!

Cells need to burn "food" to get energy to do work. For this they need glucose and oxygen. Glucose is derived from the digested food and oxygen is taken in through lungs. Both are absorbed by the blood (glucose from intestines and oxygen from lungs) and circulated to each and every cell in the body. That is the primary function of the circulatory system.

Besides it takes away the waste (carbon dioxide from cellular respiration, urea etc) from the cells...

Answer 12

heeeey don get mad at me al give u ur medal

Answer 13

no, i am not getting mad at all.....!!!

Answer 14

I was just answering yr "what does circulation have to do with food?".....

thanks for the medal :)

Answer 15

I hope now it is clear why microscopic organisms do not have a circulatory system :))

Answer 16

thanx

Answer 17

Bacteria- single celled, lives in a medium(media/animal host) which contains all nutrients sufficient for their growth. They take in materials (nutrients) according to their need by diffusion , pinocytosis and phagocytosis. so they don't need a circulatory system.
Amoeba, paramecium, euglena- Have a voccoule system which transport and excrete .....
Porifera(multi-cellular)- all cells are arranged in a form, as they lines a cavity......so they can take in and excrete what they need.
Other organisms like insects, nematodes , etc have body fluids inside a cavity from which nutrients are taken in.

Answer 18

Yup!. It's all down to physics and the mean distance molecules have to diffuse. In a single cell organism there is a good chance that oxygen will be able to reach the inside of a single cell without being metabolized. However the same is not true for much larger organisms. Increasing size means increasing complexity of circulatory systems to keep the respiring celld no more than a few microns from an oxygen supply. Small invertebrates can get by with a haemocoel. Larger invertebrates like insects evolved tracheoles, echinoderms evolved a water vascular system, larger animals still evolved respiratory pigments and pumping systems. All this so respiring cells could remain no more than 100 microns from oxygen.

Answer 19

Diffusion

Answer 20

General rule of thumb - diffusion works over distances of up to 1mm (in humans at least). In microscopic animals, diffusion works fast enough.