Biology A1.1.4

00:00Hello everyone, this is Hannah

00:02from revision dojo and today

00:04we're going to be looking

00:04at Silvis Point A1 .1

00:06.4. This is the adhesion

00:08of water to materials that

00:09are polar or charged and

00:11the impacts for organisms. Okay,

00:13so let's get an understanding

00:14of what this term adhesion

00:16means. So as water molecules

00:18also stick to other substances,

00:21this aids in a process

00:22known as capillary action and

00:24this helps water move through

00:25plant vessels. So water can

00:27pass

00:28through the pores in the

00:29structure of the soil. So

00:31I want you guys to

00:31imagine just a dry bit

00:33of soil. So this is

00:34initially going to be dry

00:35and if we either water

00:37the soil or if it

00:38rains, this becomes wet with

00:40that water. And as it

00:42does, it is a going

00:44to be drawn through the

00:45roots to be transported for

00:47the vessels. And also this

00:49water maintains not only the

00:51wetness of the soil, but

00:52also the wetness of the

00:53structures. And then when water

00:55evaporates,

00:56Another portion of water can

00:58then be also absorbed to

00:59what this part of the

01:00plant that is evaporated up

01:02through the plant. And this

01:04keeps the moisture of the

01:05structure providing a life medium.

01:08Okay, so let's look at

01:09a few of these definitions

01:10in a bit more detail.

01:12So we have looked at

01:13adhesion. Now let's also look

01:18at what polar means. Let's

01:20look at what an ion

01:21is. And let's also differentiate

01:23between

01:24the cation and an anion.

01:32Okay, so as we mentioned,

01:33adhesion is essentially the ability

01:34of water to stick to

01:35other molecules so it can

01:37be useful for transport. Now,

01:39a polar molecule is essentially

01:41this arises from when there

01:44is an unequal sharing of

01:46electrons between atoms and a

01:48molecule. Now, a classic example

01:50of this is our water.

01:52molecules are polar molecules. We

01:54also have glucose molecules. This

01:56is another classic example of

01:58a polar molecule, whether it's

02:00an unequal sharing of electrons

02:01between atoms and the molecule.

02:05Okay, now these polar molecules,

02:08they result in a slightly

02:09negative or a slightly positive

02:11charge. We define that as

02:13delta negative or delta positive.

02:17Now let's look at what

02:18an ion is. Now an

02:19ion is a

02:20essentially when electrons either leave

02:23an atom or join an

02:25atom. Now, with an ion,

02:28we're not going to have

02:28this partially negative or partially

02:30positive charge. We're going to

02:31have a completely negative or

02:33a completely positive charge, which

02:35brings us onto our next

02:36point, which is cations and

02:38anions. Now, these are pretty

02:40much interconnected. Both of these

02:43with the ions, because a

02:44cation is a positively charged

02:46ion and an anion

02:48is a negatively charged aisle.

02:50So what happens with a

02:51counteron is electrons leave the

02:53atom. So we have loss

02:56of electrons resulting in an

02:57overall positive charge. And then

02:59with an anion, we have

03:01electrons going to that atom.

03:04So we have an overall

03:06negative charge. OK. Now, let's

03:12look at the impact of

03:14adhesion for organisms.

03:16So as I was mentioning

03:18before, there is a process

03:20known as capillary action. So

03:23let's look at this process

03:24in a bit more detail.

03:31Capillary action. So capillary action

03:39is essentially the movement of

03:41water through a narrow space

03:43and this is

03:44often in opposition to external

03:46forces like gravity. So I

03:49want you guys to think

03:50about the trees and the

03:52plants that you see outside

03:53on a daily basis. Now

03:55these trees and plants they

03:56could not thrive without capillary

03:58action. Because capillary action is

04:00what helps bring water into

04:02the roots with the help

04:03of adhesion and cohesion. Water

04:06and dissolved ions, they can

04:07move all the way down

04:09from the roots all the

04:10way up to the leaves

04:12and the

04:12branches. And you can imagine

04:15that this is essential for

04:17water to travel to the

04:19organisms, especially our plants and

04:20trees, because without this water,

04:22they will not be able

04:23to survive.