TPO10 Lecture 3 Ecology
Narrator
Listen to part of a lecture in an Ecology Class.
Professor
So we’ve been talking about nutrients, the elements in the environment that
are essential for living organisms to develop, live a healthy life and reproduce.
Some nutrients are quiet scarce; there just isn’t much of them in the
environment. But fortunately they get recycled. When nutrients are used over
and over in the environment, we call that a nutrient cycle. Because of the
importance of nutrients and their scarcity, nutrient recycling is one of the most
significant eco-system processes that will cover in this course. The three most
important nutrient recycles are the nitrogen cycle, the carbon cycle and the
one we are going to talk about today, the Phosphorus cycle.
So the Phosphorus cycle has been studied a lot by ecologists because like I
said, Phosphorus cycle is a most important nutrient and it’s not so abundant.
The largest quantities are found in rocks at the bottom of the ocean. How the
Phosphorus get there? Well, let’s start with the Phosphorus in rocks. The rocks
get broken down into smaller and smaller particles as they are weathered.
They are weathered slowly by rain and wind over long periods of time.
Phosphorus is slowly released as the rocks are broken down and then it gets
spread around into the soil. Once it’s in the soil, plants absorb it through their
roots.
Student
So that’s the reason people mine rocks that contain a lot of Phosphorus to help
the agriculture?
Professor
Hum, they mined the rock, artificially break it down and put the Phosphorus
into the agricultural fertilizers. So humans can play a role in a first part of the
Phosphorus cycle -- the breaking down of rocks and the spreading
Phosphorus into the soil by speeding up the rate at which this natural process
occurs. You see. Now after the Phosphorus is in the soil, plants grow. They
use Phosphorus from the soil to grow. And when they die, they decompose.
And the Phosphorus is recycled back into the soil; same thing with the
animals that eat those plants, or eat other animals that have eaten those
plants. We call all of this – the land phase of the Phosphorus cycle. But a lot
of the Phosphorus in the soil gets washed away into rivers by rain and melting
snow. And so begins another phase of the cycle. Can anyone guess what it
is called? Nancy
Nancy
Well, if the one is called the land phase, then this has to be called the water
phase, right?
Professor
Yes, that’s such a difficult point isn’t it? In a normal water phase, rivers
eventually empty into oceans, and once in the oceans, the Phosphorus gets
absorbed by water plants like algae. Then fish eats the algae or eat other fish
that have eaten those plants. But the water phase is sometime affected by
excessive fertilizers. If not all of Phosphorus gets used by the crops and larger
amounts of Phosphorus gets into the rivers. This could cause a rapid growth of
water plants in the river, which can lead to the water waste getting clogged with
organisms, which can change the flow of the water. Several current studies are
looking at these effects and I really do hope we can find the way to deal with
this issue before these ecosystems are adversely affected. Ok? Of course,
another way that humans can interrupt the normal process is fishing. The
fishing industry helps bring Phosphorus back to land. In the normal water
phase the remaining Phosphorus makes its way, settles to the bottom of the
ocean and gets mixed into the ocean sediments. But remember, this is a cycle.
The Phosphorus at the bottom of the ocean has to somehow make its way
back to the surface, to complete the cycle, to begin the cycle all over again.
After millions of years, powerful geological forces, like under water volcanoes
lift up the ocean sediments to form new land. When an under volcano pushes
submerge rock to the surface, a new island is created. Then over many more
years the Phosphorus reach rocks of the new land begin to erode and the
cycle continues.
Guy
What about, well, you said that the nitrogen cycle is also an important nutrient
cycle. And there is a lot of nitrogen in the atmosphere, so I was wondering, is
there a lot of Phosphorus in the atmosphere too?
Professor
Good question, George. You’re right to guess the Phosphorus can end up in
earth atmosphere. It can move from the land or from the oceans to the
atmosphere, and vice versa. However, there’s just not as substantial amount of
it there, like there is with nitrogen, it’s a very minimal quantity.
TPO10 Lecture 4 Psychology
Narrator
Listen to part of a lecture in a Psychology Class.
Professor
OK. If I ask about the earliest thing you can remember, I will bet for most of you,
your earliest memory would be about from age of 3, right? Well, that’s true for
most adults. We cannot remember anything that happened before age of 3.
And this phenomenon is so widespread and well-documented it has a name. It
is called child amnesia and it was first documented in 1893.
As I said, this phenomenon refers to the adults not being able to remember the
childhood incidents. It’s not children trying to remember events from last month
or last years. Of course you follow that if you can’t remember incidents as your
child, you probably won’t remember as an adult. OK, so … why is this? What is
the reason from the child amnesia? Well, once a popular explanation was that
child memories are always repressed and memories are disturbing so that is
adults we keep them in barricade. And so we can recall them and this is base
on…well it’s not base on, on, on… the kind of self-research in the lab testing
we want to talk about today. So let’s put that explanation aside and
concentrate on just two. OK? It could be that as children we do form memories
of things prior to age of 3, but forget as we get grew older, let’s one explanation.
Another possibility is that children younger than 3 lack some cognitive capacity
for memory. And that idea, that children are unable to form memories that have
been the dominant belief psychology for the past 100 years. And this idea is
very much tied to things, the theory of Jean Piaget and also to language
development in children.
So PRJ’s theory of cognitive development--- PRJ’s suggested that because
they don’t have language, children younger than 18-24 months leave in the
here and now that is they lack the mean to symbolic represent object, and
events, that will not physically presented. Everybody get that? PRJ proposed
that young children don’t have way to represent things that aren’t wide in front
of them. That’s what language does, right? Words represent things, ideas.
Once language started to develop for about age 2, they do has a system for
symbolic representation and can talk about things which are not in there in
immediate environment including the past. Of course he didn’t claim that
infants don’t have any sort of memory it is acknowledged that they can
recognize some stimuli, like faces. And for many years this model were very
much in favors in psychology, even thought memory tests were never
performed on young children.
Well, finally in the 1980s, study was done. And this study show that very young
children under age of 2 do have capacity for recall. Now if we children cannot
talk, how was the recall tested? Well, that is a good question, since the
capacity for recall has always been linked with the ability to talk. So the
researcher set up an experiment using imitation based texts. The adults use
probable toys or other objects to demonstrate action that has 2 steps. The
children were asked to imitate the steps immediately and then he again after
lays off one or month. And even after delay, the children could…couldn’t call or
replicate the action, the objects they used, and the steps involved and the
order of the steps. Even children young is 9 months, now, test showed that
there was a faster way of forgetting among the youngest children but most
importantly it shows that the development of the recall did not depend on
language development. And that was the importance finding. I guess I should
add that the findings, don’t say there was no connection between the
development of language and memory. There are some of evidence that are
being able to talk about the event does lead to having a strong memory of that
event. But that does not seem the real issue here.
So, back to our question about the cause of the childhood amnesia, well, there
is something called the rate of forgetting. And childhood amnesia may reflect
high rate of forgetting, in other words, children under age of 3 do form memory
and do so without language. But they forget the memories at a fast rate,
probably faster than adults do. Researcher has set standards….sort of
unexpected rate of forgetting, but that expected rate was set based on the
tests done on the adults. So what is the rate of forgetting for children under the
age of 3? We expected to be high, but the tests disproved these really haven’t
been done yet.
