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Biology library
Course: Biology library > Unit 36
Lesson 1: Crash Course: Biology- Why carbon is everywhere
- Water - Liquid awesome
- Biological molecules - You are what you eat
- Eukaryopolis - The city of animal cells
- In da club - Membranes & transport
- Plant cells
- ATP & respiration
- Photosynthesis
- Heredity
- DNA, hot pockets, & the longest word ever
- Mitosis: Splitting up is complicated
- Meiosis: Where the sex starts
- Natural Selection
- Speciation: Of ligers & men
- Animal development: We're just tubes
- Evolutionary development: Chicken teeth
- Population genetics: When Darwin met Mendel
- Taxonomy: Life's filing system
- Evolution: It's a Thing
- Comparative anatomy: What makes us animals
- Simple animals: Sponges, jellies, & octopuses
- Complex animals: Annelids & arthropods
- Chordates
- Animal behavior
- The nervous system
- Circulatory & respiratory systems
- The digestive system
- The excretory system: From your heart to the toilet
- The skeletal system: It's ALIVE!
- Big Guns: The Muscular System
- Your immune system: Natural born killer
- Great glands - Your endocrine system
- The reproductive system: How gonads go
- Old & Odd: Archaea, Bacteria & Protists
- The sex lives of nonvascular plants
- Vascular plants = Winning!
- The plants & the bees: Plant reproduction
- Fungi: Death Becomes Them
- Ecology - Rules for living on earth
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Vascular plants = Winning!
Hank introduces us to one of the most diverse and important families in the tree of life - the vascular plants. These plants have found tremendous success and the their secret is also their defining trait: conductive tissues that can take food and water from one part of a plant to another part. Though it sounds simple, the ability to move nutrients and water from one part of an organism to another was a evolutionary breakthrough for vascular plants, allowing them to grow exponentially larger, store food for lean times, and develop features that allowed them to spread farther and faster. Plants dominated the earth long before animals even showed up, and even today hold the world records for the largest, most massive, and oldest organisms on the planet. Created by EcoGeek.
Want to join the conversation?
- AtHank says Ground tissue does photosynthesis but how can it get light if there is Dermal Tissue on the outside layer? Is the dermal tissue transparent? 3:08(19 votes)
- Very good question. I might not be the right person to answer this, and I could be wrong, but I think photosynthesis does not require all of the visible light, but only some energy from the light. There are wavelengths of the light that will continue through the dermal tissue. I suppose the energy from those light waves contain enough energy to keep the photosynthesis going.(15 votes)
- How do you know if a plant is a female or a male?(10 votes)
- Examine several flowers from the plant. Because a plant may have male and female flowers you will need to examine several to help determine the gender of the plant. look for the stamen and anther inside the flower. the anther is a pollen sac that sits on top of a stalk. the entire structure is called the stamen and is the male part of the flower. look in the center of the flower for a pistil, the female parts. the pistil is composed of an ovary as the base that is thick and round, a style ( the stalk ) and the stigma at the top. The stigma collects the pollen that fertilizes the plant. remember that not all plants are one or the other, these plants are called dioecious plants.(7 votes)
- How can you find out the age of a plant or tree?(6 votes)
- cut it open and count the numbers of rings in a stem.(9 votes)
- Is grass a vascular plant? What are vascular plants?(3 votes)
- Yes, Grass is a vascular plant. And a vascular plant is a plant that is characterized by the presence of conducting tissue .
I hope I could answer your question correctly :)(6 votes)
- when the plants make glucose as starce then don't they have to break it by respiration?(3 votes)
- plants makes starch for storage so that they can use it later on when there aren't enough for them to function (for eg. winter) and they do break it down by respiration.(6 votes)
- Athe mentions the 200,000 years old patch of sea gras. How do they know how old it is? 2:11(5 votes)
- Scientists tested its radioactive materials and using a very complex equation, and volia! They figured it out.(3 votes)
- Are sclerenchyma cells the cells that make up bark?(2 votes)
- no, sclerenchyma cells are internal supporting cells--ground tissue. Bark is just a nontechnical term for all the tissues outside of the vascular cambium.(6 votes)
- At, Hank explains that transpiration causes negative pressure, which draws water upwards through the xylem. In my bio textbook, however, I learned that water is drawn upwards through cohesion. Which is right? 6:21(3 votes)
- In vascular plants, water is mainly "pulled" up by transpiration. Water in the leaves evaporate creating a "negative pressure" that can suck water columns up to great heights. The strong cohesive property of water makes it possible for the water column to hold, even at large heights.
Root pressure causes water to be "pushed" up through the xylem and into the leaves. However, this pressure is very small compared to transpirational pull, and so is only effective in short, herbaceous plants, where water column in xylem is much shorter.(2 votes)
- When Hank says the Ground Tissues store leftover food, does he mean the nutrients?(3 votes)
- Whats the difference between vascular and unvascular plants?(2 votes)
- There is no such thing as 'unvascular' plants; you are referring to 'nonvascular' plants instead.
Vascular plants have a vascular system, i.e. a phloem and xylem. While non-vascular plants do not have a vascular system, they may have specialized systems for the uptake of water and mineral ions. Liverworts are an example of nonvascular plants.
Hope I helped.(3 votes)
Video transcript
- [Hank] This is yarrow. A flowering plant found all
over the Northern Hemisphere. Its feathery leaves have
natural astringent properties. And its scientific name, Achillea, comes from Achilles the Greek hero who's said to have used it on
the wounds of his soldiers. And this is Snake grass,
otherwise known as Horsetail, or to the kids, Pop grass 'cause you can just pop it apart and then put it back together again. Although on top there, it's dead now. And this is a Ponderosa pine. One of my favorite trees, it can grow hundreds of feet tall. And on a warm day, if you sniff it, it smells like butterscotch. They all have different
shapes, sizes and properties but each of these things
is a vascular plant, one of the most diverse, and dare I say, important families in the tree of life. Since their predecessors
first arrived on the scene, some 420 million years ago,
vascular plants have found tremendous success through
their ability to exploit resources all around them. They convert sunshine into food, They convert nutrients
directly through the soil without the costly process of digestion, and they even enlist
the help of some friends when it comes to reproduction. So often, when they're doing their thing, it involves a third party, which like, you know, good for them. But these things alone can't
explain vascular plants' extraordinary evolutionary success. I mean, algae was
photosynthesizing long before plants made it fashionable. And as we learned last
week, nonvascular plants have reproductive strategies
that are tricked out six ways from Sunday. So, like what gives? The secret to vascular plant
success is their defining trait conductive tissues that
can take food and water from one part of a plant
to another part of a plant. This may sound simple
enough, but the ability to move stuff from one part
of an organism to another was a huge evolutionary
breakthrough for vascular plants. It allowed them to grow
exponentially larger, store food for lean times, and
develop some fancy features that allowed them to
spread farther and faster. It was one of the biggest
revolutions in the history of life on earth. The result: plants
dominated earth long before animals even showed up. And even today, they hold
most of the world records. The largest organism in
the world is a redwood in Northern California. 115 meters tall, bigger
than three blue whales laid end to end. The most massive organism
is a grove of quaking aspen in Utah all connected by
the roots, weighing a total of 13 million pounds. And the oldest living
thing, a patch of sea grass in the Mediterranean dating
back 200 thousand years. We spend a lot of time
congratulating ourselves on how awesomely magnificent and complex the human animal is, but you guys, I got to hand it to you. (upbeat music) So you know by now, the
more specialized tissues an organism has the more complex they are and the better they typically do. But you also know that these changes don't take place overnight. The tissues that define vascular plants didn't evolve all at once,
but today we recognize three types that make
these plants what they are. Dermal tissues make up
their outermost layers and help prevent damage and water loss. Vascular tissues do all that conducting of materials I just mentioned. And the most abundant
tissue type, ground tissues, carry out some of the most important functions of plant life, including photosynthesis and
the storage of leftover food. Now, some plants never
go beyond these basics. They sprout from a
germinated seed and develop these tissues, and then stop. This is called primary growth,
and plants that are limited to this stage are herbaceous. As the name says, they
are like herbs, small, soft, and flexible, and typically
they die down to the root, or die completely after
one growing season. Pretty much everything you
see growing in a backyard garden, herbs and flowers and broccoli and that kind of stuff,
those are herbaceous. But a lot of vascular plants
go on to secondary growth, which allows them to grow,
not just taller, but wider. This is made possible
by the development of additional tissues,
particularly woody tissues. These are your woody
plants, which include shrubs and bark covered vines, called lianas, and of course, your trees. But no matter how big
they may or may not grow, all vascular plants are
organized into three main organs. All of which you are
intimately familiar with, not just because you knew
what they were when you were in second grade, but also because you probably eat them every day. First, the root. It absorbs water and nutrients
and serves as a pantry of leftover food, and of course keeps the plant anchored in the ground. Next, the stem. It contains structures
that transport fluids and store nutrients and also,
is home to specialized cells, called meristems that are responsible for creating new growth. But their most important task is to support the last organ: the leaf. This, of course, is
where the plant exchanges gasses with the atmosphere
and collects sunlight to manufacture food,
with the help of water and minerals collected through the root and sent up through the stem. Now each of these organs
contains all three tissues which together, work to
absorb, conduct, and exploit one of the worlds most
important molecules: water. So, since plants are pretty
much designed around water lets follow some H2O to see
how plants make the most of it. First, as with most organisms,
nothing can get in or out of a plant without getting past the skin. In this case the dermal tissue. In smaller, non-woody
plants, most of this is just a thin layer of cells called,
fittingly, the epidermis. Naturally, this is great
for keeping the outside out, and the inside in, but the
epidermis can also sport some snazzy feature in different
parts of the plant. In leaves and stems, for
example, it often has a waxy outer layer called a cuticle
that helps prevent water loss. On some leaves, or on pods
that hold those valuable seeds, the epidermis can sprout
hair-like structures called trichomes that
help keep insects at bay and secret toxic or sticky fluids. The same secretions that make the yarrow useful for first aid, for
instance, are also what discourage ants from using it for lunch. Finally in the root, the
epidermis has similar features called root hairs that maximize the roots' surface area for absorption, just like we've seen in
our own organ systems. This, of course, is where
they plants generally absorb the water they need. By the way, the cells that
make up this dermal tissue are the most basic
essential building blocks of vascular plants called parenchyma, or visceral flesh cells. These are the most
abundant plant cells found, not just in roots, but also
in stems, leaves, and flowers. They are thin and flexible and can perform all kinds of functions
depending on their location. Now, after passing through
the skin of the root, and through it's starchy
cortex or outer layer, water arrives in the first of two kinds of vascular tissue: the xylem. The xylem's main function is
to carry water and dissolve minerals from the root up to the leaves. But like, how? How, by Zeus' beard, can
plants make water defy gravity? Well, a lot of the reason is that up top, the plant is continuously
evaporating water through a process called evapotranspiration. As water evaporates from the leaves, which I'll explain in greater
detail when we get up there, it creates negative
pressure inside the xylem which draws more water upwards. Plants can transpire truly
staggering amounts of water, and it's because of this that
our atmosphere is habitable. A single acre of corn gives off about 3,000 gallons of water every day. A large oak tree, just
one tree, can transpire 40,000 gallons in a year. Only 1% of the water that
plants absorb is actually used by plants, mostly in photosynthesis, the rest is slowly,
and invisibly released, providing one of earth's
most crucial functions. Transporting water from the
soil into the atmosphere where it then returns
to the surface as rain, making all life possible. Yeah. Chew on that as we continue up the xylem. And as we get higher in the plant, we begin to encounter a
great diversity of cells, designed not only for moving stuff around, but also for providing structural support. For instance, elongated cells
with thicker cell walls, called collenchyma, help
hold up the plant body, especially in herbaceous plants and young structures like new shoots. Celery is mostly made up of these cells, so you already know what they taste like. In larger, woody plants, you
also find sclerenchyma cells, especially in the xylem. These have even thicker
cell walls made from lignin, a super strong polymer
that makes wood woody. What's weird about
sclerenchyma cells, though, is that most of them, when they reach maturity, they die. They just leave behind
their hardy cell walls as a support structure,
and new cells from a fresh layer during the next
growing season push the old, dead layer outward. In warm, wet years,
these layers grow thick, while in cold, dry years
they're light and thin. These woody remains form tree rings, which scientists can use, not only to track the age of a tree,
but also the history of the climate that it lived in. Now, at the top of the xylem, water arrives at it's final
destination: the leaf. Here, water travels
through an increasingly minuscule network of vein-like structures until it's dumped into
a new kind of tissue called the mesophyll. As you can tell from it's
name, meso meaning middle, and phyll meaning leaf,
this layer sits between the top and the bottom epidermis of the leaf, forming the bacon in the BLT
that is the leaf structure. This, my friends, marks our
entry into the ground tissue. I'm sure you're as excited
about that as I am. Despite it's name, ground
tissue isn't just in the ground, and it's actually just
defined as any tissue that's either not dermal or vascular. Regardless of this low billing though, it's where the money is,
and by money, I mean food. And the mesophyll is chock
full of parenchyma cells of various shapes and sizes
and many of them arranged loosely to let CO2 and other
materials flow between them. These cells contain the
photosynthetic organelles chloroplasts, which as you know, host the process of photosynthesis. But, where is this CO2 coming from? Well, some of the neatest
features on the leaf are these tiny opening in
the epidermis called stomata. Around each stoma are two guard cells, connected at both ends that
regulate it's size and shape. When conditions are dry,
the guard cells are limp, they stick together, closing the stoma. But, when the leaf is flush with water, the guard cells plump up
and bow out from each other, opening the stoma to
allow water to evaporate, and let carbon dioxide in. This is what allows
evapotranspiration to take place, as well as photosynthesis. And you remember photosynthesis. Through a series of brain
wrackingly complicated reactions sparked by
the energy from the sun, the CO2 combines with hydrogen from the water to create glucose. The leftover oxygen is
released through the stomata and the glucose is ready for shipping. Now, if you've been paying attention, you noticed that earlier
I said that there are two kinds of vascular tissue, and here the circle is
made complete as the sugar exits the leaf through the phloem. The phloem is mostly made of cells stacked in tubes with perforated
plates at either end. After the glucose is
loaded into these cells, called sieve cells, or
sieve tube elements, they then absorb water
from the nearby xylem to form a rich, sugary sap
to transport the sugar. This sweet sap, by the way, is what gives the Ponderosa it's delicious smell. By way of internal pressure and diffusion, the sap travels wherever it's needed, to parts of the plant experiencing growth during the growing season
or down to the root if it's dormant, like during winter, where it's stored until spring. So now that you understand
everything that it takes for vascular plants to succeed, I hope you see why plants equals winning. And I'm not just talking about them sweeping the contest
for biggest, heaviest, oldest living things, though again, congrats on that guys. Plants are not only responsible for like making rain happen,
they're also the first, and most important link in our food chain. And that's why the world's
most plant-rich habitats, like rainforests and grasslands, are so crucial to our survival. When those habitats
change, everything changes. Weather, food supply, even
incidents of natural disasters. So, I, for one, welcome
our plant overlords, because they've done a great job so far making life on earth possible. But, I know you're curious, how do different kinds of
plants make more plants? That's all about the birds and the bees, which is what we'll be
talking about next week.