Shadowing Practice: Stroll Through the Playlist (a Biology Review) - Learn English Speaking with Video

בחר מצב תרגול

כל מצב פותח חדר תרגול במסך מלא.

535 משפטים

אם המשפטים קצרים או ארוכים מדי, לחץ על ערוך כדי להתאים אותם.

Petunia, we have so many videos now.

Every once in a while, I'll come across one of your pictures and be reminded all about the topic again.

I love them so much.

Aw, thanks.

Remember the danger guppy?

I love the danger guppy.

Which video was that for?

Classification!

Remember we were talking about how a scientific name is much more reliable than a common name?

Especially a made-up common name.

Oh, yeah.

Sometimes I forget what I've drawn.

You forget?

Well, every video has, like, 200 pictures.

If I don't go back and watch the videos, I tend to forget.

And I mean, we have, like, more than 50 videos, so that would take a long time.

I guess I'd be more inclined to do that if we had, like, a TLDR version.

A what?

You know, too long, didn't read, a summary of sorts.

Like a refresher, just covering the main points.

A refresher?

Now wait a minute, I didn't mean that we actually need to create a- We do!

I mean, we've made quite a few videos now in our biology playlist.

And if someone was reviewing, we could have this recap video, this stroll through the playlist.

Yeah, but- Now this one video would be way longer than our short videos, obviously, but it could be a useful study tool to connect the main pieces of the content together.

Granted, it would only have main points, not everything.

I guess that would be helpful.

I just don't think we, uh- Also, this stroll would be meant to be paused a lot.

There's so much vocabulary in biology.

We'll get Gus in on this.

He can hold up the pause sign so people know

when to pause the video so we can even ask the viewer questions.

And if the questions are difficult to answer, that may be a good indicator to check out the video it corresponds to.

Are you ready to stroll, Petunia?

Actually, this is going to be kind of a brisk stroll.

And because it only covers a short part of each concept, never forget biology is full of more exceptions and details than we can cover.

But that's great for more exploring.

We start with the characteristics of life.

What makes an organism alive?

Or not alive, anyway?

Life is difficult to define, and there are so many exceptions in looking at characteristics of life.

We went through some characteristics between my bathtub-grown pony and a real pony, but we didn't want to put numbers on the characteristics of life

because we didn't want to suggest that these are the only characteristics that one could argue.

So here's your first pause question.

Can you think of some characteristics of life to include?

We also note it in the video that they could certainly be titled differently, but here they are.

But this may get you to thinking of what's alive and what's not.

When studying biology, the study of life, it's important to understand the biological levels of organization.

Meaning these levels start small.

The smallest living unit being the cell.

That's part of the cell theory after all.

The cell theory includes that the cell is the smallest living unit in all organisms, that all living organisms are made up of cells, and what else?

Ah yes, that all cells come from pre-existing cells.

So cells combined together make up tissues.

Tissues make up organs.

Organs make up organ systems.

Organ systems are part of an organism.

An individual organism.

Individuals can be part of a population.

They're all the same species.

A community can you keep leveling up?

So the next larger level after community would be ecosystem.

At that level you're including abiotic factors which are non-living factors.

Rocks or temperature.

Next level is biome.

And then with biomes combined, all parts of the living world?

The biosphere.

Let's focus on living organisms.

are part of living organisms.

We mentioned four of these major macromolecules.

Can you name them here with their building blocks?

Carbohydrates, lipids, proteins, and nucleic acids.

And here are their building blocks.

Monosaccharides, fatty acid and glycerol, amino acids, and nucleotides.

These building blocks are considered true monomers for carbs, proteins, and nucleic acids.

Can you think of some important functions for any of these biomolecules?

Okay, Petunia, bring out some functions.

These are just some functions.

We wouldn't exist without these large molecules of life.

And their structures are just beautiful.

We included a popular mnemonic to remember some of the major elements they contain in their structures as well.

Most enzymes are made of proteins.

Can you describe some of the vocabulary associated with the enzyme?

Well, you can see this enzyme has an active site where a substrate binds.

Enzymes can speed up reactions.

Enzymes have the ability to break down or build up the substrates that they act upon. And ta-da!

Products.

An example of why we care?

Well consider the specific different digestive enzymes that are specific for breaking down fats or sugars or proteins.

But enzymes typically have a specific temperature and pH range that they need to be in to work correctly.

And what happens if enzymes can't stay in their ideal temperature or pH range?

That's right, they can denature.

Enzymes play a major role within cells.

We have oh so many videos on cells that you may wish to explore.

We explain the differences between prokaryotic cells and eukaryotic cells using the popular mnemonic

that pro rhymes with no and u rhymes with do, but what does that actually reference to?

cells have no nucleus, nor the other fancy membrane-bound organelles.

But ewe rhymes with do, and eukaryotic cells do have a nucleus and other membrane-bound organelles.

Prokaryotes include bacteria, anarchaea.

100

Eukaryotes include plants, animals, protists, and fungi.

101

Can you think of some things that prokaryotic cells would have in common with eukaryotic cells?

102

So just to name a few, DNA, cytoplasm, ribosomes, and a cell membrane would be included in both.

103

In our Intro to Cells video, we explore a lot of membrane-bound organelles that would be found exclusively in eukaryotes such as the nucleus,

104

endoplasmic reticulum, Golgi apparatus, and mitochondria.

105

Plant cells and animal cells can have some differences between them as well.

106

Let's consider the cell membrane, also known as a plasma membrane.

107

It is a part of all living cells, so why is it so important?

108

Remember all cells have a membrane, regardless of whether or not they may have a cell wall.

109

The membrane is a big deal for homeostasis because it controls what goes in and out of the cell.

110

The membrane is made up of these phospholipids which have polar heads and nonpolar tails.

111

Some molecules move passively through the membrane without a need for added energy.

112

That's called passive transport.

113

Simple diffusion and facilitated diffusion, which is through a protein, are examples of passive transport.

114

In those cases, solutes travel with the gradient.

115

Active transport, though, can involve using ATP to force molecules to move in the opposite direction of the gradient.

116

So is this example simple diffusion, facilitated diffusion, or active transport?

117

And how do you know?

118

Well, it's not active transport because you can tell the molecules are traveling with the gradient without a need for ATP.

119

It's not simple diffusion because it does seem to require a protein.

120

It's facilitated diffusion, and that's passive.

121

Water molecules can travel directly across a semi-permeable membrane, as they are so small.

122

Or they can travel through proteins called aquaporins.

123

That is more efficient.

124

Water traveling through the membrane is called osmosis.

125

In peak diffusion, water molecules do travel from an area where there is a

126

high concentration of water molecules to an area of low concentration of water molecules.

127

But we mentioned there's another way to look at osmosis.

128

You can also look at it as water traveling to areas where there is a higher solute concentration, as the water concentration is less there.

129

So to determine the net movement of water in osmosis, look for the hypertonic area.

130

The areas of high solute concentration.

131

A cell that is placed in a salty solution can lose water

132

because the net movement of water is to the area of high solute concentration.

133

One reason why you should not drink a lot of salt water.

134

It's very dehydrating.

135

Check to see if you can explain this graphic using the vocabulary hypertonic, hypotonic, and isotonic.

136

Let's move beyond the membrane here and take a look at these organelles.

137

the mitochondria and chloroplast.

138

In eukaryotes, cellular respiration involves the mitochondria and photosynthesis involves the chloroplast.

139

Cellular respiration involves the breakdown of glucose to yield ATP.

140

All organisms must make ATP in some way or another.

141

Yes, this includes plants and amoebas.

142

If oxygen isn't available, some organisms like bacteria or yeast can do anaerobic respiration or fermentation to make their ATP.

143

So what do these chemical equations have in common?

144

Well one thing that is interesting is that these reactants and products are switched here, although that doesn't mean they are simply the reverse of each other.

145

Keep in mind that they have different steps within them that make them very different.

146

produces glucose.

147

Sugar.

148

Using sunlight energy.

149

Not everything can do photosynthesis.

150

In eukaryotic cells it occurs in the chloroplast.

151

So moving beyond the mitochondria and chloroplast, let's take a look at this nucleus of a eukaryotic cell.

152

Guess what's in here?

153

DNA.

154

DNA is a nucleic acid and nucleic acids are one of the types of biomolecules.

155

It contains your genetic information and your entire DNA code is found in almost all of your cells, although genes can be turned on or off in different cells.

156

Let's zoom into the monomer of DNA, a nucleotide.

157

Nucleotides have a phosphate, deoxyribose, and a nitrogenous base.

158

Which part of this nucleotide do you think is critical for determining genetic information?

159

Yep, the base.

160

Well that is the sequence of them.

161

And this mnemonic, apples in the tree, cars in the garage, can help you remember that the bases adenine and thymine pair together.

162

Cytosine and guanine pair together.

163

DNA can be tightly coiled and condensed into these units called chromosomes.

164

The number of chromosomes in humans is 46.

165

How many do you receive from each parent?

166

Well you would receive 23 from the female parent and 23 from the male parent.

167

That's really important later on when we talk about cell division because chromosomes are more portable when it comes to cells dividing.

168

Zooming back out, DNA is made up of two anti-parallel strands.

169

One strand runs 5' to 3' and the other strand runs 3' to 5'.

170

Now your body cells have to make copies of their DNA.

171

Why?

172

When you make a new body cell, which you make body cells for growth and repair, you need DNA to go into that new body cell as that is its genetic material.

173

Hence the need for DNA replication.

174

Making more DNA.

175

We have some major key player enzymes here.

176

Can you remember what these key players do?

177

DNA must be unwound by an enzyme called helicase.

178

Primase is an enzyme that sets down primers.

179

Primers are needed because another enzyme, called DNA polymerase, requires them in order to start building.

180

DNA polymerase builds a new strand in the 5' to 3' direction only.

181

And because of that directional building, one of these new strands will be a lagging strand as

182

DNA polymerase has to keep racing up here next to where the unwinding is going on.

183

This causes fragments on the lagging strand known as okazaki fragments.

184

Ligase can eventually be involved in sealing those fragments together.

185

So we mentioned that you have to replicate DNA before you make new cells.

186

It's a controlled event that happens in something known as the cell cycle.

187

Do you remember the cell cycle phases often shown in a pie chart like this?

188

The cell cycle includes G1 , S phase synthesis of DNA that's when the DNA replicates,

189

G2 cell grows some more to prepare for dividing, and then M phase which includes mitosis and phytokinesis.

190

G1S and G2 are all part of interphase, so the cell is not dividing during that time.

191

But once it enters M phase, it divides.

192

There are checkpoints it controls whether a cell can continue through the cycle.

193

If a cell doesn't meet the checkpoint requirements, it is either fixed or it must undergo apoptosis, which means the cell destroys itself.

194

This highly regulated cell cycle is controlled by many different proteins.

195

Some that we mentioned included CDK, cyclin, and p53.

196

Cancer cells are body cells that do not respond correctly to these checkpoints and tend to divide out of control.

197

They can also have other problems such as making too much of their own growth factors, not anchoring properly, and not functioning correctly.

198

Now we mentioned this cell cycle has emphase which includes mitosis.

199

So what is mitosis?

200

Mitosis is part of cell division.

201

What kind of cells does it make?

202

In humans and many other organisms, it makes identical body cells.

203

Like skin cells making skin cells or stomach cells making stomach cells.

204

Great for growth of an organism or replacement of worn out cells.

205

During mitosis, chromosomes, which are condensed forms of DNA and protein, can be moved more easily into the newly formed daughter cell.

206

We went over the PMAT mnemonic to remember the stages.

207

Prophase, metaphase, anaphase, and telophase.

208

Cytokinesis splits the cytoplasm and completely divides the actual cell.

209

What's really easy to confuse with mitosis?

210

Meiosis.

211

Kind of wish they didn't sound so close.

212

Anyway, what kind of cells does meiosis make?

213

In humans and many other organisms, meiosis makes gametes, which are critical for sexual reproduction, otherwise known as sperm and egg cells.

214

These gametes have half the number of chromosomes as a body cell.

215

Gametes are haploid, meaning they have one set of chromosomes.

216

Body cells are diploid, meaning they have two sets of chromosomes.

217

PMAT happens twice here in meiosis.

218

You have your starting cell here, which is diploid, it goes through prophase 1, metaphase 1, anaphase 1, and telophase 1.

219

Then cytokinesis happens and it makes two cells.

220

Then those cells go through prophase II, metaphase II, anaphase II, and telophase II.

221

After cytokinesis, this results in four haploid cells, as these sperm cells shown here.

222

These cells are all different from each other due to independent assortment and a process known as crossing over.

223

So what is crossing over again and when does it happen?

224

over happens during prophase I and it's when pairs of homologous chromosomes can transfer information between each other.

225

So since meiosis is an important process for making sperm and egg cells for sexual reproduction in humans and many other organisms,

226

how is this involved with the alleles and genes that a baby organism may inherit?

227

Remember that in humans, a sperm cell has 23 chromosomes and an egg cell has 23 chromosomes.

228

When they come together in a fertilized egg, that is 46 chromosomes.

229

Portions of the chromosomes are genes that can code for specific traits.

230

Many traits actually involve multiple genes.

231

Genes can come in varieties known as alleles.

232

Alleles are forms of a gene.

233

For example, we talk about the trait of tasting or not tasting the chemical PTC.

234

If treating this as a single gene trait, we would say the gene is a PTC tasting gene.

235

But the allele that could be on a chromosome, which is a form of a gene,

236

could be tasting or non-tasting In Mendelian inheritance,

237

recessive alleles are expressed if the dominant allele is not present.

238

So someone who inherits a homozygous dominant genotype of T, T would have a phenotype that is PTC tasting.

239

What would the phenotype be of these other two?

240

Someone who inherits a heterozygous Tt genotype would have a phenotype that is also PTC tasting.

241

Only someone who inherits a homozygous recessive little t, little t genotype would have a phenotype that is non-PTC tasting.

242

Again assuming it's a single gene trait, and as we mentioned in the video, it may be more complex than that.

243

So speaking of alleles and genes, it's time for the super brisk stroll through different types of genetics that we have covered.

244

We started with basic Mendelian, monohybrid, and dihybrid crosses.

245

Could you explain, in your own words, how to complete these Punnett squares and how to write out the genotype and phenotype ratios of the offspring?

246

To get help with the answer to these questions, check out the videos on these two topics specifically because there are multiple steps to solving these.

247

Then we talked about some non-Mendelian inheritance including sex-linked traits and multiple alleles.

248

If these look unfamiliar, you might want to review these videos as well.

249

We also mentioned incomplete dominance and codominance.

250

What is the difference between incomplete dominance and codominance?

251

This graphic may help.

252

Notice in codominance both alleles are expressed.

253

In incomplete dominance, you can see how the phenotype can have an almost in-between

254

appearance of the two traits there is not complete dominance when both of these alleles are present.

255

Finally, we have a video on pedigrees.

256

Pedigrees can be used to track a trait of interest, whether it be a sex-link trait or an autosomal trait.

257

In a pedigree, individuals that are females are represented by circles, males are represented by squares,

258

and individuals that have the trait being tracked are represented by circles or squares that are shaded.

259

Now, when we're talking about these fascinating traits, you might wonder, How does DNA actually code for your traits?

260

Well DNA can code for proteins and proteins are involved with many traits.

261

Proteins are involved in transport, in structure, in acting as enzymes that make all kinds of materials, in protecting the body, and so much more.

262

Your eye color is due to proteins involved in pigment production.

263

So protein synthesis, that is, making proteins, is a big deal.

264

Do you remember the two major steps in protein synthesis?

265

The first step is transcription, which makes mRNA within the nucleus.

266

The second step is translation, which takes place in the ribosome and makes a chain of amino acids known as a polypeptide.

267

Proteins can be made up of one or more of these polypeptide chains.

268

We also mention other forms of RNA, such as rRNA and tRNA,

269

as well as how to read a codon chart to determine which amino acids are produced.

270

Proteins often need folding to be fully functional.

271

We have a video clip on protein structure and folding too.

272

Now, on the subject of this codon chart, you will notice that the bases are read in 3s to determine a specific amino acid.

273

These three bases on the mRNA are known as a codon.

274

tRNA has an anti-codon on it that complements the mRNA codon.

275

tRNAs also carry the corresponding amino acid.

276

But what if there is a mutation in the DNA or mRNA?

277

When we talk about mutations, we first mention gene mutations.

278

This can include substitution, deletion, or insertion.

279

Do you remember which of these are more likely to result in a frameshift mutation?

280

A frameshift is a shift in the reading frame.

281

Bases are read in 3s, so a frameshift mutation is more commonly caused by an insertion or deletion.

282

If you add or delete a base, it's possible to change the entire reading frame, depending on where it occurs.

283

With substitution, you typically would only affect one codon.

284

Now not every change in the base means the amino acid will be different.

285

See how all of these codons still code for the amino acid leucine?

286

We also discussed chromosomal mutations.

287

Can you name and describe some chromosomal mutations?

288

We mentioned duplication, deletion, inversion, and translocation.

289

As mentioned, mutations can be neutral.

290

They can also be harmful or potentially even beneficial.

291

But the mutations are random.

292

The organism doesn't will itself to mutate or have some certain trait.

293

This is a good time to talk about natural selection.

294

Take these frogs sitting on logs.

295

They are all the same species.

296

There can be variety, though, within the species due to processes like independent assortment and crossing over during meiosis or from mutations.

297

The frogs in this population with a darker color blend into this particular environment more easily.

298

A predator may have a higher chance of consuming the lighter, easier to see green frogs.

299

The darker green frogs may have more fitness than the lighter frogs.

300

Fitness in the biological sense is determined by not how strong they are or how long they live, but by how many offspring they have.

301

These darker green frogs pass down their DNA to their offspring.

302

The new baby frogs will have DNA from their parents.

303

The lighter green frogs are being selected against since they are easier to see in this particular habitat.

304

Over a long period of time, you could expect to see a higher frequency of darker frogs in the population.

305

This mechanism of evolution is known as natural selection, which acts on populations.

306

So how does natural selection compare to genetic drift?

307

Well, both genetic drift and natural selection are mechanisms of evolution.

308

In natural selection, organisms of traits that result in high reproductive fitness tend to be more frequent in a population over time.

309

But with genetic drift, the organisms that survive and have offspring were randomly selected.

310

They are not necessarily more biologically fit.

311

Instead it's more that the organisms won the game of chance from an event.

312

Check out the bottleneck effect and founder effect, which are forms of this.

313

We mention in our natural selection video an example involving bacteria

314

and antibiotic resistance that continues to be a great concern in our world.

315

But let's talk more about bacteria in general.

316

Bacteria are unicellular prokaryotes.

317

Some can make their own food, they're autotrophs, and some consume organic material, they're heterotrophs.

318

Being prokaryotes, they don't have a nucleus or other membrane-bound organelles, but they still have genetic material, cytoplasm, and ribosomes.

319

Bacteria can come in a range of shapes.

320

Bacteria often get a reputation for being bad pathogens, and there are many that can be, although not all bacteria are harmful,

321

bacteria can also be very helpful for organisms and ecosystems.

322

Can you think of some examples of bacteria being helpful?

323

Some examples of helpful bacteria roles include breaking down food in our digestive system, acting as decomposers, making some foods that we eat,

324

and fixing nitrogen for plants.

325

But as for harmful bacteria, they can be treated with antibiotics.

326

Examples of bacterial infections include strep throat, tooth decay, or tetanus.

327

When we start thinking about bacteria, our minds may wander to viruses.

328

How are bacteria and viruses similar, and how are they different?

329

If you watch our viruses video, you will hear some reasons why viruses are not considered to be living organisms.

330

Although debate still exists on calling them non-living.

331

Unlike bacteria, viruses are not prokaryotes.

332

Viruses don't even consist of cells.

333

But viruses do have genetic material, DNA or RNA.

334

Viruses typically have a protein coat known as a capsid.

335

Some viruses have envelopes.

336

And some diseases that viruses cause include the common cold, HIV, or influenza .

337

Unlike bacteria, though, viruses don't respond to antibiotics.

338

While bacteria can reproduce by splitting in something called binary fission, viruses actually require a host to reproduce.

339

Viruses reproduce using the lytic or lysogenic cycle.

340

Definitely something to revisit if you have forgotten.

341

While viruses are not considered to be living organisms, bacteria are.

342

So are archaea, protists, fungi, plants, and animals.

343

We mentioned that archaea are unicellular prokaryotes and many can live in extreme environments.

344

They can be either autotrophs or heterotrophs.

345

Protists are mostly unicellular but can be multicellular.

346

This diverse group can be made up of autotrophs or heterotrophs.

347

Fungi are typically multicellular but they can be unicellular.

348

Fungi are heterotrophs.

349

Many can act as decomposers.

350

We'll get to plants and animal systems a bit later.

351

So how do we classify living organisms?

352

First of all, all of life can be organized into three domains.

353

Can you recall what those domains are?

354

Those domains are bacteria, archaea, and eukarya.

355

Consider looking at the classification video to refresh your memory of characteristics of these domains.

356

But we can get more specific than domains, right?

357

Can you remember those taxonomy levels that come after domain?

358

They are Kingdom, Phylum, Class, Order, Family, Genus, and Species.

359

And this was our mnemonic to help you remember, but you may have one that is more memorable.

360

The thing about classification is that it is changing as we learn more about relatedness from DNA evidence.

361

Scientific names tend to be able to be used everywhere, often having Latin or Greek roots,

362

and they're definitely more reliable than common names which can vary by language or location or in this case, be completely made up.

363

Let's take some time to focus on a kingdom that provides a significant amount of the oxygen that we breathe.

364

A talented kingdom of autotrophs, which means they make their own food.

365

Plants.

366

And if they are going to make their own food using photosynthesis, they are definitely going to need to have structure that helps them to do so.

367

To do photosynthesis, plants need water.

368

How do they get water?

369

Non-vascular plants get their water by osmosis kind of like soaking up water like a sponge.

370

How is that different from a vascular plant?

371

Vascular plants have two major types of vessels, the xylem which carries water, and the phloem which can carry photosynthesis products such as sugar, throughout the plant.

372

How about light?

373

We mentioned that plant cells have chloroplasts to capture light energy.

374

To do photosynthesis, plants need carbon dioxide.

375

Many plants have these fascinating little openings, Pores really called stomata.

376

Stomata have a major role in gas exchange.

377

Gases like carbon dioxide can flow in through these openings.

378

Guard cells can control the opening and closing of the stomata.

379

When might stomata need to be closed?

380

One example is on a very hot day when the plant has low water.

381

So staying on the topic of plants, how do they reproduce?

382

Well, many plants can reproduce asexually as mentioned with my spider plants.

383

But many plants, spider plants included, can reproduce sexually.

384

We only covered sexual reproduction in flowering plants at the time of this stroll, otherwise known as reproduction in angiosperms.

385

Angiosperms typically have petals to attract pollinators and many offer nectar to attract them as well.

386

Many angiosperms have sepals which protect the developing flower bud.

387

Okay, so do you remember the male and female parts that can be within a flower structure?

388

Male parts of the flower include the anther and filament.

389

This whole thing here is the stamen.

390

Female parts of the flower include the stigma, style, and ovary.

391

The whole thing here is the pistil.

392

Can you describe the pollination and fertilization process in angiosperms using those terms?

393

Simplified a bit, pollen is brought from an anther to the sticky stigma possibly by a pollinator.

394

That's pollination.

395

Next comes fertilization.

396

For this to happen, a pollen tube is formed.

397

A generative cell from the pollen can divide into two sperm cells,

398

which can travel down the stile to the ovary into an ovule where one sperm cell will fertilize an egg, giving rise to a zygote.

399

Inside the ovule, another sperm cell will fertilize two polar nuclei, which gives rise to the endosperm.

400

The endosperm provides food for the the baby plant.

401

Because this fertilization process involves sperm cells joining two different things, the egg and the polar nuclei, we call this double fertilization.

402

These fertilized ovules can develop into seeds.

403

The ovary can give rise to a fruit, and that fruit can be very useful for helping the seeds get dispersed.

404

But while angiosperms bear fruit, keep in mind it may not be how you might imagine a fruit.

405

So we talked about plant structure and how some plants reproduce.

406

We already mentioned how plants provide a lot of oxygen that we breathe.

407

But it's not just about oxygen.

408

Plants are also critical as part of food chains and food webs.

409

As autotrophs, plants are producers.

410

If you remember in a food chain we start with producers, then we move into consumers which are heterotrophs.

411

Heterotrophs have to consume other things.

412

So we have primary consumers, secondary consumers, tertiary consumers, we could keep going.

413

The arrows point to the direction of the energy flow.

414

We could arrange this into an energy pyramid.

415

The producers at the base here in TLE 1 actually contain the most energy.

416

The primary consumers here in TCl2 actually only receive approximately 10% of the energy from the level below.

417

Meaning, let's say you have plants here that had 10,000 kilocalories of energy.

418

Can you complete the rest of the pyramid with approximately how much of the energy would be within each TCl?

419

Well the next level here, the primary consumers in TCl2, would only receive 1,000 kilocalories of energy.

420

The secondary consumers in TLC3 would receive 100 kcal of energy.

421

Tertiary consumers in TLC4 would receive approximately 10 kcal of energy.

422

Energy can be lost as heat or undigested.

423

Ecosystems typically do not have a single food chain.

424

Instead they tend to have a food web.

425

A food web is made up of multiple food chains that interact together.

426

This can show the importance of biodiversity.

427

variety of organisms living in a given area.

428

Biodiversity can contribute to the sustainability of a community, but how do they develop?

429

This takes us to our ecological succession video.

430

Ecological succession is a process, over time, of organisms in an ecological community.

431

In primary succession, the area this is happening in generally is brand new without soil.

432

An example could be a volcano lava flow that has cooled and left behind this new area with and no soil present.

433

Usually you have a pioneer species which is a name for the species it colonizes first.

434

Lichen or moss, for example.

435

After pioneer species colonize the area, they slowly break down rock into smaller,

436

more plant-friendly substrate, and over time contributing more organic matter in newly formed soil which will support plants.

437

Small vascular plants like grasses can come in, shrubs can follow, then trees.

438

continue to move into the area.

439

How long this takes can vary, but it's often hundreds of years before you get a climax community going.

440

So how is this different from secondary succession?

441

With secondary succession, you're talking about an area that once had plants and animals and an ecological community going on.

442

But then there is an ecological disturbance such as a forest fire or human activity.

443

The soil is still there and that's kind of the big key point here

444

because your initial species starting out could be small plants as there is already soil there.

445

Secondary succession can then follow a similar sequence to primary succession after that point.

446

See our video for more details and an understanding of why this succession sequence tends to happen.

447

Communities make up ecosystems and in order for these ecosystems to function, we've got to have cycling.

448

You probably learned about the water cycle in elementary school.

449

Learning about the carbon cycle and the nitrogen cycle tends to be explored later on in junior high or high school.

450

So let's recap that from our nitrogen and carbon cycle video.

451

Carbon is often known as a building block in life.

452

You will find it in the four big biomolecules.

453

Can you think of examples where you might find carbon?

454

Some examples.

455

Carbon is dissolved in the ocean.

456

It is in rocks and fossil fuels.

457

It is in living organisms.

458

It can be in the atmosphere.

459

There's carbon dioxide in the atmosphere.

460

It is taken in by organisms that perform photosynthesis.

461

If the photosynthetic organism is eaten by an animal, it becomes part of that animal too.

462

And the animal that eats that animal.

463

Both the plants and animals do cellular respiration which releases carbon dioxide.

464

When the plants and animals die, the carbon can be released and stored in sediment.

465

Over a very long time, they can even be converted into fossil fuels.

466

The burning of fossil fuels produces carbon dioxide, and this has also led to the concern of excessive carbon dioxide in the atmosphere.

467

Now for nitrogen.

468

Nitrogen is important in building proteins and nucleic acids.

469

Let's look at how it can cycle.

470

Nitrogen can be found in the atmosphere, but it needs to be fixed before it can be used well.

471

Some plants have nitrogen-fixing bacteria living in their roots.

472

The nitrogen is fixed by these bacteria into a form of nitrogen known as ammonia and ammonium.

473

Nitrifying bacteria in the soil can convert the ammonium to nitrates and nitrites, forms of nitrogen that plants can also easily use and assimilate.

474

Animals can eat those plants and obtain nitrogen.

475

When both plants and animals decompose, decomposers help return ammonia and ammonium to the soil in a process known as ammonification where it can be reused again.

476

There are also denitrifying bacteria.

477

In denitrification, they can convert nitrates and nitrites back into nitrogen gas.

478

This is just one example of cycling.

479

But keep in mind that this happens in both aquatic and terrestrial environments.

480

So you can see there's a balance with these elements and living organisms in an ecosystem.

481

Let's talk about some of the ecological relationships among living organisms.

482

In the ecological relationships video, I mentioned my fascination with antlions.

483

Antlions are predators of ants.

484

Ants are their prey.

485

This is known as predation.

486

Antlions have to compete with other predators like this jumping spider, for example.

487

Competing for a food resource is an example of competition.

488

We also mentioned three symbiotic relationships.

489

Symbiotic relationships are specific types of relationships where different species live together.

490

Can you recall what occurs in the three symbiotic relationships that we mentioned?

491

In commensalism, one organism benefits and the other is neither helped nor harmed.

492

It's neutral.

493

Many barnacle species can attach themselves to moving things.

494

On a free whale ride, this barnacle can get access to food since it's a filter feeder and the whale may travel to nutrient-rich waters.

495

However, in this example, with this particular whale and these barnacles, the whale was neither are helped nor harmed.

496

In parasitism, one organism benefits and the other one is harmed by a parasite.

497

Parasites can live inside or on their host.

498

Mutualism is an example of a symbiotic relationship where both organisms involved benefit.

499

Our example had been an acacia tree being protected by acacia ants.

500

The acacia tree provides a home and possibly nutrients.

501

But you know, one of my favorite examples of mutualism is the good bacteria.

502

We can live in our digestive system and help us digest our food.

503

So speaking of systems in the human body, our short video on that topic only goes into basic functions of 11 body systems.

504

Here they are up here for you in alphabetical order.

505

Can you give a general function for each of these?

506

The circulatory system helps transport gases and nutrients.

507

The digestive system is involved with both the mechanical and chemical breakdown of food.

508

The endocrine system is involved with producing important signals known as hormones.

509

The excretory system is involved with excreting waste material as done by the kidneys or skin.

510

The immune lymphatic system helps defend our body against pathogens such as viruses and harmful bacteria.

511

The integumentary system, long fancy word for a large organ, your skin, can protect against water loss and serve as a barrier.

512

The muscular system is involved with allowing for movement.

513

The nervous system coordinates both voluntary and involuntary responses.

514

The reproductive system allows for the ability to reproduce.

515

The respiratory system is involved with gas exchange.

516

And the skeletal system is critical for structure and support.

517

Those are very basic functions mentioned, and of course this doesn't include structures.

518

But the big takeaway we hope you have from our body systems video is that these systems don't work in isolation.

519

They work together.

520

If you're nervous about a test, which we hope you're not because we have confidence that you're going to do great, but if you were nervous, you can get an adrenaline rush.

521

Your endocrine system secretes adrenaline, a hormone that can cause your heart involved in the circulatory system to speed up its beating.

522

Your breathing rate, which is involved with your respiratory system, can increase.

523

These are all systems working together.

524

And that's relevant for the end.

525

Because in this stroll through our playlist, you've seen how we've been connecting these concepts together.

526

Because that's the thing that is so cool about biology.

527

It's all connected.

528

We hope this video helps you identify your strengths and areas that you might want to go back and explore.

529

We also hope that you recognize that beyond any test you're studying, it is so important to be able to answer, why does this content matter?

530

If there is a topic in this video that still doesn't seem to matter beyond just studying for a test, please check out our full video on that topic because that's something

531

that we really try to address in each and every video.

532

Don't forget we also have a video with study strategies that you might want to check out, and we have helpful gif animations and comics on our website that you might find useful.

533

And if you are studying for something big, it is our sincere amoebic wish that you will feel confident about your learning.

534

Well, that's it for the Amoeba Sisters, and we remind you to stay curious.

535

Thank you.

הורד אפליקציה

כל מה שאתה צריך כדי לדבר בשטף

הגיית AIציון לכל משפט

תרגול IPAשלוט בכל צליל

אוצר מיליםבנה את מאגר המילים שלך

משחק אוצר מיליםלמד תוך כדי משחק

סרוק QR

Download on theApp Store Get it onGoogle Play

אותו ערוץ

Mitosis vs. Meiosis: Side by Side Comparison

Daily ConversationUniversity Students

Mitosis: The Amazing Cell Process that Uses Division to Multiply! (Older Video 2016 )

IELTS PrepTOEFL PrepUniversity Students

Circulatory System and Pathway of Blood Through the Heart

Cambridge Exam PrepHigh School StudentsUniversity Students

FOR YOU

המלץ על סרטון

109 משפטים

אוצר מילים והערות הגייה לשיעור הזה

שיעור הדיבור הזה ברמה B2 מבוסס על הסרטון “Stroll Through the Playlist”. המילים שחוזרות הכי הרבה: cell, plant, organism, dna, bacteria. בסרטון הזה יש 535 משפטים ו-6317 מילים לתרגול Shadowing. הדיבור נמשך 41:19. הדובר מדבר בקצב טבעי של כ-153 מילים בדקה, קרוב לשיחה יומיומית. רק 76% מהמילים נמצאות בין 3,000 המילים הנפוצות ביותר באנגלית, כך שאוצר המילים מאתגר.

אוצר מילים מרכזי בסרטון הזה

15 המילים המתקדמות ביותר בסרטון, עם ההגייה והמשמעות שלהן:

מילה	הגייה	משמעות
organism שם עצם	/ˈɔɹ.ɡəˌnɪz.əm/	אוֹרְגָּנִיזְם, יְצוּר
bacterium שם עצם	/bækˈtɪəɹ.ɪəm/	חַיְדַּק \ חידק
trait שם עצם	/tɹeɪt/	מאפיין, תכונה
membrane שם עצם	/ˈmɛm.bɹeɪn/	קרום
enzyme שם עצם	/ˈɛn.zaɪm/	אנזים
chromosome שם עצם	/ˈkɹoʊməˌsoʊm/	כְרוֹמוֹזוֹם
nitrogen שם עצם	/ˈnaɪ.tɹə.d͡ʒən/	חַנְקָן
mutation שם עצם	/mjuˈteɪʃən/	מוּטַצְיָה
reproduce פועל	/ˌɹi.pɹəˈdus/	התרבה
molecule שם עצם	/ˈmɑ.lɪ.kjul/	מוֹלֵקוּלָה
photosynthesis שם עצם	/ˌfoʊ.toʊˈsɪn.θə.sɪs/	פוטוסינתזה
ecological שם תואר	/ˌiːkəˈlɒd͡ʒɪkl̩/	אֶקוֹלוֹגִי
characteristic שם עצם	/ˌkæɹ(ə)ktəˈɹɪstɪk/	סממן
meiosis שם עצם	/maɪˈoʊ.sɪs/	מִיוֹזָה
mitosis שם עצם	/maɪˈtoʊ.sɪs/	מִיטוֹזָה

Phrasal verbs שתשמעו

מילה	משמעות
check out פועל	בדק

משפטים שכדאי לחזור עליהם

משפטים קצרים ושלמים מהסרטון שאפשר להשתמש בהם בשיחה יומיומית:

A community can you keep leveling up?
Can you name them here with their building blocks?
An example of why we care?
How many do you receive from each parent?
Can you remember what these key players do?

דקדוק בסרטון הזה

המבנים שהדובר משתמש בהם הכי הרבה, עם המילים המדויקות מהסרטון:

מבנה	בסרטון
סביל (Passive voice) be + past participle — הדגש הוא על מה שקורה, לא על מי שעושה את הפעולה	be reminded · would be meant · be titled
משפטי זיקה (Relative clauses) who / which + clause — מידע נוסף על אדם או דבר	factors which are · phospholipids which have · diffusion, which is
הווה מושלם (Present perfect) have/has + past participle — פעולה שקרתה בעבר ועדיין יש לה חשיבות או השפעה עכשיו	I've drawn · we've made · have covered

הגייה ששווה לשים לב אליה

הדובר משתמש ב-40 קיצורים וצורות מקוצרות, כמו don't, you're, didn't. אמרו אותם בצורה הקצרה, כפי שאתם שומעים אותם.

הצלילים של “th”: photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/, synthesis /ˈsɪnθəsɪs/, anther /ˈæn.θɚ/
הצלילים של “sh” ו-“zh”: mutation /mjuˈteɪʃən/, succession /səkˈsɛʃ.ən/, diffusion /dɪˈfju.ʒən/, respiration /ɹɛspɪˈɹeɪʃən/, reproduction /ˌɹiːpɹəˈdʌkʃən/
מילים ארוכות — שימו לב להטעמה: organism /ˈɔɹ.ɡəˌnɪz.əm/, photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/, ecological /ˌiːkəˈlɒd͡ʒɪkl̩/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/, heterotroph /ˈhɛtəɹəˌtɹoʊf/

צלילים שדוברי עברית מתקשים בהם:

/æ/ — פתוח יותר מה-“אֶ” העברית, לא כמו “a” ב-“cup”: bacterium /bækˈtɪəɹ.ɪəm/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/, angiosperm /ˈæn.d͡ʒi.əˌspɝm/, prokaryote /pɹoʊˈkæɹi.oʊt/, strand /ˈstɹænd/
/r/ — הלשון לא נוגעת בשום מקום, לא ה-“ר” הגרונית: organism /ˈɔɹ.ɡəˌnɪz.əm/, bacterium /bækˈtɪəɹ.ɪəm/, trait /tɹeɪt/, membrane /ˈmɛm.bɹeɪn/, chromosome /ˈkɹoʊməˌsoʊm/
/ŋ/ בסוף מילה — צליל אפי בלי “ג” בסוף: offspring /ˈɔfspɹɪŋ/, fixing /ˈfɪksɪŋ/

איך לתרגל עם הסרטון הזה

הקשיבו לכל הסרטון פעם אחת בלי לדבר, ורשמו את המילים שאתם לא מכירים.
התחילו במהירות 0.75×, תרגלו Shadowing משפט אחר משפט, וחזרו למהירות רגילה כשזה מרגיש קל.
הקליטו את עצמכם והשוו למקור, תוך תשומת לב למילים כמו organism, bacterium, trait.

מהי טכניקת השאדואינג?

שאדואינג היא טכניקת למידת שפה מבוססת מדע שפותחה במקור להכשרת מתורגמנים מקצועיים ופופולרית על ידי הפוליגלוט ד"ר אלכסנדר ארגואלס. השיטה פשוטה אך עוצמתית: אתה מקשיב לאודיו באנגלית ילידית וחוזר עליו בקול רם מיד — כמו צל העוקב אחרי הדובר עם עיכוב של 1–2 שניות בלבד. בניגוד להאזנה פסיבית או תרגילי דקדוק, שאדואינג מכריח את המוח והשרירים בפה לעבד ולשחזר דפוסי דיבור אמיתיים בו זמנית. מחקרים מראים שזה משפר משמעותית את דיוק ההגייה, האינטונציה, הקצב, הדיבור המחובר, הבנת השמיעה ושטף הדיבור — מה שהופך אותו לאחת השיטות היעילות ביותר להכנה לIELTS Speaking ולתקשורת באנגלית בעולם האמיתי.

טכניקת Shadowing: קרא את המדריך המלא שלב אחר שלב →

Shadowing Practice: Stroll Through the Playlist (a Biology Review) - Learn English Speaking with Video

בחר מצב תרגול

הורד אפליקציה

אותו ערוץ

Endocrine System

Mitosis vs. Meiosis: Side by Side Comparison

Mitosis: The Amazing Cell Process that Uses Division to Multiply! (Older Video 2016 )

Circulatory System and Pathway of Blood Through the Heart

המלץ על סרטון

The Land Down Under – A Virtual Field Trip (Quiz Edition)

How to Learn More in 2 Hours Than Most Do in a Full Day

Learn English with Disney's A BUG'S LIFE — Meet the Circus Bugs

3. Endangered WB

Introduction to Chemistry

Unit 6- BioblitzReading (Reading Explorer 1 3rd Ed) Video

How Plants Grow

idk what im doing with my life (and that's ok)

Human Body Podcast | Learn English with Science 🧠💡| B1

GLOBAL SUCCESS 5 - UNIT 4: OUR FREE - TIME ACTIVITIES - VOCABULARY

GCSE Biology - Drug Development and Testing - Clinical Trials (2026/27 exams)

I Speedran NEW BEE BIOME in 99 Nights in the Forest!