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Biology library
Unit 1: Lesson 1
Welcome to biology!Biology overview
Overview of biology, the study of life.
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What exactly does he mean at2:15?(11 votes)
He means that everything is made up of cells--plants, animals, humans, everything. It's kind of like saying that legos are the building blocks of LegoLand.(20 votes)
is a virus a living thing?(11 votes)
No Mark..a virus is not a living thing, it's just a complex molecule composed of different types of proteins, nucleic acids and carbs.
So the viruses can't produce their own energy, that's the reason they dominate living cells- to get energy.(17 votes)
How did living things come to life?(11 votes)
Earth was able to support life only after the planet had cooled enough for a rocky crust to solidify. Once that happened, water vapor from volcanoes condensed in the atmosphere, fell as rain, and collected on the Earth’s surface. Besides water vapor, volcanoes also produced gases rich in the basic ingredients of life: carbon, hydrogen, oxygen, and nitrogen. Toxic gases such as ammonia and methane were common. At this point, Earth's early atmosphere consisted entirely of these volcanic gases, and there was no free oxygen. In the primordial “soup” of the early seas, organic molecules concentrated, formed more complex molecules, and became simple cells.
The transition from complex organic molecules to living cells could have occurred in several environments. Small, warm ponds are one possibility, but recent work has suggested that deep-sea hydrothermal vents, such as those found along mid-ocean spreading centers today, may have been the cradle of Earth's life. These environments contain the chemicals and the source of energy needed to synthesize more complex organic structures. Although scientists have not succeeded in creating life from organic molecules in the laboratory, they have reproduced many of the intermediate steps.
So what were the first living things and when did they appear? Studies of genetic material indicate that a living group of single-celled organisms called Archaea may share many features with early life on Earth. Many Archaea now live in hot springs, deep-sea vents, saline water, and other harsh environments. If the first organisms resembled modern Archaea, they also may have lived in such places, but direct evidence for early life is controversial because it is difficult to distinguish between complex inorganic structures and simple biological ones in the geologic record. The oldest evidence for life may be 3.5-billion-year-old sedimentary structures from Australia that resemble stromatolites. Stromatolites are created today by living mats of microorganisms (mostly cyanobacteria, or blue-green algae). These primitive organisms trap thin layers of sediment with their sticky filaments and grow upward to get light for photosynthesis. Modern-day examples of stromatolites can be found in waters off Australia, the Bahamas, and Belize.
In the Archean structures, layers similar to those seen in living stromatolites are evident, and secondary structures interpreted as simple filamentous microfossils have been recovered from the layers. The biotic origin of the structures has, however, been questioned. Both the supposed Archean stromatolites and the microfossils may have been produced by inorganic processes. Regardless, uncontested microfossils and chemical traces of life were present at least by 2.7 billion years ago. Stromatolites that were produced by microorganisms are abundant later in the Archean and throughout the Proterozoic. These sedimentary structures, formed by organic processes, provide important evidence of early life. At present, we can say with certainty that life had evolved by 2.7 billion years ago, and possibly as early as 3.5 billion years ago.(17 votes)
Are we really "alive" if we are made up of inanimate material?(23 votes)
@Eric song. I have an idea for you to change your mind read genesis chapter one though 5 then tell me what you learned bro(0 votes)
- The test said:"The properties shared by all living things are: They are made up of cells."
But virus don't have cell structures and virus are living things?
so ?(16 votes)- My classmate always says: "VIRUSES ARE DEAD!". He's right that they're not alive, but dead would mean that they at some point have died..
But viruses are not living things, because they don't have the same characteristics as living thing do. So the only thing they can do is to command the cell to reproduce them, which the cell does until there are so many, the cell bursts.
There are two different kinds of viral infection 'methods'. Lytic and lysogenic.
Lytic is the scenario when the virus goes into the cell, rapidly reproduce itself, and burst right away.
Lysigenic infection is when the virus goes into the cell, replicates itself along with the cell's DNA for even years before it breaks out and the cell bursts.(2 votes)
What is the purpose of Bio- Engineering?(12 votes)
Possibly bio-weapons, or making more questions than answers. also problems too.(8 votes)
- What are the branches of Biology?(8 votes)
The classification of subdisciplines and interdisciplines it consists of is extensive.
I think this may help you have one glance at a time:
http://www.iasplanner.com/civilservices/ias-pre/general-science/main-branches-of-biology-and-fields-of-biology(8 votes)
- How does cell division actually create new cells from just splitting?(8 votes)
- Mitosis is a part of the cell cycle in which chromosomes in a cell nucleus are separated into two identical sets of chromosomes, and each set ends up in its own nucleus, hence creating new cells.(8 votes)
- What type of metabolic reactions take place in plasma lemma which makes it living(8 votes)
- A metabolic reaction network represents (a subset of) all metabolic reactions that occur inside a cell.In these networks, mint intracellular and mext extracellular metabolites are connected to each other through n reactions, which can be intracellular reactions or exchange reactions between the cell and the environment. The reaction rates of these reactions, the so called fluxes, are summarized in the (n × 1) flux vector v [mol/(gDW∙h)]. Growth of the cell is represented as a pseudo-reaction to biomass, which is defined as an extracellular compound, yielding mext + 1 extracellular metabolites in total. All reactions are classified as reversible or irreversible, based on thermodynamic information. All this information is represented by the stoichiometric matrix S, which contains the stoichiometric reaction coefficients. This matrix can be subdivided intoSint, Sext and Sbio, which are the row(s) corresponding to intracellular and extracellular metabolites, and biomass, respectively.(2 votes)
I don't understand why the HIV virus is coming out of the immune cell. Isn't the Immune cell supposed to get rid of the viruses, not make more?(2 votes)
AMEN BROTHER. life is so complicated, i am trying to figure out why i have not died yet(6 votes)
2:15Video transcript
[Voiceover] I would like to welcome you to Biology at Khan Academy. And biology, as you might know, is the study of life. And I can't really imagine
anything more interesting than the study of life. And when I say "life," I'm not just talking
about us, human beings. I'm talking about all animals. I'm talking about plants. I'm talking about bacteria. And it really is fascinating. How do we start off with
inanimate molecules and atoms? You know, this right here
is a molecule of DNA. How do we start with things like that, and we get the complexity
of living things? And you might be saying, well, what makes something living? Well, living things convert
energy from one form to another. They use that energy to grow. They use that energy to change. And I guess growth is a form of change. They use that energy to reproduce. And these are all, in and of themselves, fascinating questions. How do they do this? You know, we look around us. How do we, you know, eat a muffin? And how does that allow us to move around and think, and do all the things we do? Where did the energy from
that muffin come from? How are we similar to
a plant or an insect? And we are eerily or strangely similar to these things. We actually have a lot more
in common with, you know, that tree outside your window, or that insect, that bee,
that might be buzzing around, than you realize. Even with the bacteria that you can only even see at a microscopic level. In fact, we have so much bacteria as part of what makes us, us. So these are fascinating questions. How did life even emerge? And so over the course of what you see in Biology on Khan Academy, we're going to answer these fundamental, fascinating questions. We're going to think
about things like energy and the role of energy in life. We're going to think about
important molecules in biology. And perhaps most importantly, DNA and its role in reproduction
and containing information. And we're going to study cells, which are the basic
building block of life. And as we'll see, even
though we view cells as these super, super small, small things, cells in and of themselves
are incredibly complex. And if you compare them
to an atomic scale, they're quite large. In fact, this entire blue
background that I have there, that's the surface of an immune cell. And what you see here emerging from it, these little yellow things. These are HIV viruses,
emerging from an immune cell. So even though you imagine cells as these very, very
small microscopic things, this incredible complexity. Even viruses. Viruses are one of
these fascinating things that kind of are right on the
edge between life and nonlife. They definitely reproduce,
and they definitely evolve. But they don't necessarily
have a metabolism. We'll learn a lot more about that. They don't necessarily
use energy and growth in the same way that we
would associate with life. And then perhaps one of the
biggest questions of all is how did life come about? And we will study that as we look at evolution
and natural selection. So welcome to Khan
Academy's Biology section. I think you're going
to find it fascinating. You're going to realize
that biology, in some way, is the most complex of the sciences. And in a lot of ways, the one
that we understand the least. It's going to be built
on top of chemistry, which in turn is built on top of physics, which in turn is built
on top of mathematics. And biology is one of our Frankly, even in the last hundred years, we're just starting to scratch the surface of understanding it. But what's really exciting is where the field of biology is going. As we understand things at a deeper level, at a molecular level, we're going to start thinking about how can we even do things
like engineer biology, or affect the world around us? It's going to raise all sorts of fascinating and deep
and ethical questions. So, hopefully you enjoy this. Biology is one of the most, arguably, maybe the most fascinating subject of all. I don't want to offend the chemists and the physicists out there. I actually find those
quite fascinating as well. But we're going to answer, or
attempt to start to answer, some of the most fundamental
questions of our existence.