Shadowing Practice: Stroll Through the Playlist (a Biology Review) - Learn English Speaking with Video
Creating lesson...
1
Petunia, we have so many videos now.
2
Every once in a while, I'll come across one of your pictures and be reminded all about the topic again.
3
I love them so much.
4
Aw, thanks.
5
Remember the danger guppy?
6
I love the danger guppy.
7
Which video was that for?
8
Classification!
9
Remember we were talking about how a scientific name is much more reliable than a common name?
10
Especially a made-up common name.
11
Oh, yeah.
12
Sometimes I forget what I've drawn.
13
You forget?
14
Well, every video has, like, 200 pictures.
15
If I don't go back and watch the videos, I tend to forget.
16
And I mean, we have, like, more than 50 videos, so that would take a long time.
17
I guess I'd be more inclined to do that if we had, like, a TLDR version.
18
A what?
19
You know, too long, didn't read, a summary of sorts.
20
Like a refresher, just covering the main points.
21
A refresher?
22
Now wait a minute, I didn't mean that we actually need to create a- We do!
23
I mean, we've made quite a few videos now in our biology playlist.
24
And if someone was reviewing, we could have this recap video, this stroll through the playlist.
25
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.
26
Granted, it would only have main points, not everything.
27
I guess that would be helpful.
28
I just don't think we, uh- Also, this stroll would be meant to be paused a lot.
29
There's so much vocabulary in biology.
30
We'll get Gus in on this.
31
He can hold up the pause sign so people know
32
when to pause the video so we can even ask the viewer questions.
33
And if the questions are difficult to answer, that may be a good indicator to check out the video it corresponds to.
34
Are you ready to stroll, Petunia?
35
Actually, this is going to be kind of a brisk stroll.
36
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.
37
But that's great for more exploring.
38
We start with the characteristics of life.
39
What makes an organism alive?
40
Or not alive, anyway?
41
Life is difficult to define, and there are so many exceptions in looking at characteristics of life.
42
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
43
because we didn't want to suggest that these are the only characteristics that one could argue.
44
So here's your first pause question.
45
Can you think of some characteristics of life to include?
46
We also note it in the video that they could certainly be titled differently, but here they are.
47
But this may get you to thinking of what's alive and what's not.
48
When studying biology, the study of life, it's important to understand the biological levels of organization.
49
Meaning these levels start small.
50
The smallest living unit being the cell.
51
That's part of the cell theory after all.
52
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?
53
Ah yes, that all cells come from pre-existing cells.
54
So cells combined together make up tissues.
55
Tissues make up organs.
56
Organs make up organ systems.
57
Organ systems are part of an organism.
58
An individual organism.
59
Individuals can be part of a population.
60
They're all the same species.
61
A community can you keep leveling up?
62
So the next larger level after community would be ecosystem.
63
At that level you're including abiotic factors which are non-living factors.
64
Rocks or temperature.
65
Next level is biome.
66
And then with biomes combined, all parts of the living world?
67
The biosphere.
68
Let's focus on living organisms.
69
are part of living organisms.
70
We mentioned four of these major macromolecules.
71
Can you name them here with their building blocks?
72
Carbohydrates, lipids, proteins, and nucleic acids.
73
And here are their building blocks.
74
Monosaccharides, fatty acid and glycerol, amino acids, and nucleotides.
75
These building blocks are considered true monomers for carbs, proteins, and nucleic acids.
76
Can you think of some important functions for any of these biomolecules?
77
Okay, Petunia, bring out some functions.
78
These are just some functions.
79
We wouldn't exist without these large molecules of life.
80
And their structures are just beautiful.
81
We included a popular mnemonic to remember some of the major elements they contain in their structures as well.
82
Most enzymes are made of proteins.
83
Can you describe some of the vocabulary associated with the enzyme?
84
Well, you can see this enzyme has an active site where a substrate binds.
85
Enzymes can speed up reactions.
86
Enzymes have the ability to break down or build up the substrates that they act upon. And ta-da!
87
Products.
88
An example of why we care?
89
Well consider the specific different digestive enzymes that are specific for breaking down fats or sugars or proteins.
90
But enzymes typically have a specific temperature and pH range that they need to be in to work correctly.
91
And what happens if enzymes can't stay in their ideal temperature or pH range?
92
That's right, they can denature.
93
Enzymes play a major role within cells.
94
We have oh so many videos on cells that you may wish to explore.
95
We explain the differences between prokaryotic cells and eukaryotic cells using the popular mnemonic
96
that pro rhymes with no and u rhymes with do, but what does that actually reference to?
97
cells have no nucleus, nor the other fancy membrane-bound organelles.
98
But ewe rhymes with do, and eukaryotic cells do have a nucleus and other membrane-bound organelles.
99
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.
📺 Same Channel
B22
Endocrine System
IELTS PrepTOEFL PrepUniversity Students
C1Mitosis: The Amazing Cell Process that Uses Division to Multiply! (Older Video 2016 )
IELTS PrepTOEFL PrepUniversity Students
B2Circulatory System and Pathway of Blood Through the Heart
Cambridge Exam PrepHigh School StudentsUniversity Students
✨ Recommend Video
![[CAM 11] Test 2 Section 3](https://img.youtube.com/vi/HSliUM64x2g/mqdefault.jpg)
B23
91 sentences
[CAM 11] Test 2 Section 3
Cambridge Exam PrepHigh School StudentsUniversity Students
B21
207 sentences
I Finally Answered Your Questions
TeensDaily ConversationHigh School Students
B11
303 sentences
تعلم الانجليزية من الافلام/ SpongeBob SquarePants
TeensDaily ConversationHigh School Students
B22
109 sentences
The Land Down Under – A Virtual Field Trip (Quiz Edition)
Daily ConversationHigh School StudentsUniversity Students
B11
343 sentences
Learn English Naturally: Going for a Walk in English
Daily ConversationHigh School StudentsUniversity Students
B23
39 sentences
cam 16 test 1 part 3
Cambridge Exam PrepHigh School StudentsUniversity Students
B24
121 sentences
How To Remember EVERYTHING Like The Harvard Students (Study Less fr)
Business EnglishHigh School StudentsUniversity Students
B15
52 sentences
Life of a Tod | TootyMcNooty
High School StudentsUniversity Students
![Learn English [ American Textbook Reading Science01 ] Lesson.02 | Brian Stuart I (new 20 03 10)](https://img.youtube.com/vi/TXLnm4IsEkA/mqdefault.jpg)
B13
600 sentences
Learn English [ American Textbook Reading Science01 ] Lesson.02 | Brian Stuart I (new 20 03 10)
Daily ConversationHigh School StudentsUniversity Students
C124 sentences
Introduction to Chemistry
American AccentCambridge Exam PrepHigh School StudentsUniversity Students
B12
84 sentences
Listening Test 1. Part 3: Jess and Tom art project.
Cambridge Exam PrepHigh School StudentsUniversity Students
Vocabulary and speaking notes for this lesson
This B2 speaking lesson is built on the video “Stroll Through the Playlist”. The speaker keeps coming back to these words: cell, plant, organism, dna, bacteria. This video has 535 sentences and 6317 words to shadow. The speech runs for 41:19. The speaker talks at a natural 153 words per minute, close to everyday conversation. Only 76% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
The 15 most advanced words in the video, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| organism noun | /ˈɔɹ.ɡəˌnɪz.əm/ | A discrete and complete living thing, such as animal, plant, fungus or microorganism. |
| bacterium noun | /bækˈtɪəɹ.ɪəm/ | A single-celled organism with cell walls but no nucleus or organelles. |
| trait noun | /tɹeɪt/ | An identifying characteristic, habit or trend. |
| membrane noun | /ˈmɛm.bɹeɪn/ | A mechanical, thin, flat flexible part that can deform or vibrate when excited by an external force. |
| enzyme noun | /ˈɛn.zaɪm/ | A biomolecule that catalyses a biological chemical reaction: either a globular protein with this function or an RNA molecule with this function. |
| chromosome noun | /ˈkɹoʊməˌsoʊm/ | A linear arrangement of condensed DNA and associated proteins (such as chaperone proteins) which contains the genetic material (genome) of an organism. |
| nitrogen noun | /ˈnaɪ.tɹə.d͡ʒən/ | The chemical element (symbol N) with an atomic number of 7 and atomic weight of 14.0067. It is a colorless and odorless gas. |
| allele noun | /əˈliːl/ | One of a number of alternative forms of the same gene occupying a given position, or locus, on a chromosome. |
| mutation noun | /mjuˈteɪʃən/ | Any alteration or change. |
| reproduce verb | /ˌɹi.pɹəˈdus/ | To produce an image or copy of. |
| molecule noun | /ˈmɑ.lɪ.kjul/ | The smallest particle of a specific element or compound that retains the chemical properties of that element or compound; two or more atoms held together by… |
| succession noun | /səkˈsɛʃ.ən/ | An act of following in sequence. |
| diffusion noun | /dɪˈfju.ʒən/ | The act of diffusing or dispersing something, or the property of being diffused or dispersed; dispersion. |
| photosynthesis noun | /ˌfoʊ.toʊˈsɪn.θə.sɪs/ | Principally, oxygenic photosynthesis, any process by which plants and algae convert water and carbon dioxide into carbohydrates and waste oxygen using solar… |
| stroll verb | /stɹoʊl/ | To wander on foot; to ramble idly or leisurely; to rove. |
Phrasal verbs you will hear
| Word | Pronunciation | Meaning |
|---|---|---|
| make up verb | /ˌmeɪk ˈʌp/ | To constitute, to compose. |
| check out verb | To record the departure or withdrawal of someone or something (such as guests, employees, books, etc.). | |
| break down verb | To stop functioning. | |
| cross over verb | To pass from one side or area, physical or abstract, to another. | |
| go through verb | To travel from one end of something to the other. | |
| go back verb | To return to a place or state after having been there at a previous time. | |
| speed up verb | /spiːdˈʌp/ | To accelerate; to increase speed. |
| work together verb | To be coworkers with someone; to share a workspace with someone. |
Sentences worth repeating
Short, complete lines from the video that you can reuse in everyday conversation:
- 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?
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | be reminded · would be meant · be titled |
| Relative clauses who / which + clause — extra information about a person or thing | factors which are · phospholipids which have · diffusion, which is |
| Present perfect have/has + past participle — a past action that still matters now | I've drawn · we've made · have covered |
Pronunciation to watch
The speaker uses 40 contractions and reduced forms, such as don't, you're, didn't. Say them the short way, as you hear them.
- The “th” sounds: photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/, synthesis /ˈsɪnθəsɪs/, anther /ˈæn.θɚ/
- The “sh” and “zh” sounds: mutation /mjuˈteɪʃən/, succession /səkˈsɛʃ.ən/, diffusion /dɪˈfju.ʒən/, respiration /ɹɛspɪˈɹeɪʃən/, reproduction /ˌɹiːpɹəˈdʌkʃən/
- Long words — get the stress right: organism /ˈɔɹ.ɡəˌnɪz.əm/, photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/, ecological /ˌiːkəˈlɒd͡ʒɪkl̩/, characteristic /ˌkæɹ(ə)ktəˈɹɪstɪk/, heterotroph /ˈhɛtəɹəˌtɹoʊf/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
- Record yourself and compare with the original, paying attention to words like organism, bacterium, trait.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.