Classification of Fungi | Biological Classification | Biology | Khan Academy

Summary

This script explores the diverse kingdom of fungi, highlighting their widespread presence and unique characteristics. It delves into the classification of fungi, focusing on recent systems and discussing four major phyla: Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota. Each phylum's distinct reproductive methods, from the motile zoospores of Chytrids to the sexual conjugation of Zygomycetes, and the ascospores and basidiospores of Ascomycota and Basidiomycota, are explained. The script also touches on the importance of fungi in various industries and the dynamic nature of fungal taxonomy.

Takeaways

• 🌿 Fungi are incredibly widespread, existing in diverse environments including our homes, and can be found without even stepping outside.
• 🔬 Fungi classification has evolved significantly over time, with modern scientists using more advanced systems compared to older methods.
• 🌀 The phylum Chytridiomycota contains the simplest and most primitive fungi, characterized by their motile zoospores with flagella, unique among fungi.
• 🍞 Zygomycota, including the common bread mold Rhizopus stolonifer, reproduces both asexually through sporangiospores and sexually through a process called conjugation.
• 🍄 Ascomycetes, part of the phylum Ascomycota, are known for their sac-like ascus containing sexual spores called ascospores and are crucial in commercial applications like baking and brewing.
• 🍄 Basidiomycota, the phylum that includes mushrooms, is recognized by their club-shaped basidia which bear sexual spores known as basidiospores.
• 🍄 Sexual reproduction in fungi often involves complex processes like plasmogamy and karyogamy, leading to the formation of spores that can develop into new fungi.
• 🌱 Asexual reproduction in fungi is also common, with some phyla like Deuteromycetes lacking a known sexual phase in their life cycle.
• 🔍 The classification of fungi is dynamic and subject to change as new research and molecular analysis provide deeper insights into their evolutionary relationships.
• 🌟 Notable examples of fungi include edible mushrooms, truffles, and yeasts like Saccharomyces cerevisiae, which are used in various food and industrial processes.

Q & A

Where can you commonly find fungi?

Fungi can be found in a variety of places, including greenish-black patches on old bread, in bottles marked with 'activated yeast,' growing on damp logs in gardens, and even in water bodies or wet soils.

How has the classification of fungi changed over time?

The classification of fungi has changed dramatically over time. Scientists now refer to newer, more advanced systems of classification, which is what the video focuses on, rather than older systems.

What is the significance of the phylum Chytridiomycota?

Chytridiomycota is significant because it houses the simplest and most primitive fungi. These fungi, known as chytrids, are often unicellular organisms found in water bodies or wet soils and are unique for their motile zoospores with flagella.

What is the common name for the fungus that grows on stale bread?

The fungus that grows on stale bread is commonly known as 'common bread mold,' and it is scientifically referred to as Rhizopus stolonifer.

How do zygomycetes reproduce sexually?

Zygomycetes reproduce sexually through a process called conjugation, where two compatible haploid hyphae extend towards each other, touch, and fuse to form a zygospore containing multiple diploid nuclei.

What is the function of an ascus in ascomycetes?

In ascomycetes, an ascus is a sac-like structure that contains haploid sexual spores called ascospores. It is part of the ascocarp, which is a spore-bearing structure.

Why are ascomycetes important to humans?

Ascomycetes are important to humans because they are used in various commercial processes such as baking, brewing, and fermenting wine. One example is yeast, which is used in baking and brewing.

What are basidiomycetes and how do they reproduce?

Basidiomycetes, also known as club fungi, are characterized by their club-shaped spore-bearing structures called basidia. They reproduce sexually, with basidiospores being produced on the gills of mushrooms and released into the environment to germinate into new fungi.

Why are deuteromycetes not considered a true phylum?

Deuteromycetes, also known as imperfect fungi, are not considered a true phylum because their members are more closely related to organisms from other phyla than to each other. For example, Aspergillus, once thought to be a deuteromycete, is now classified within the phylum Ascomycota.

What is the dynamic nature of fungi classification?

Fungi classification is dynamic and ever-changing, as it is based on ongoing research and molecular analysis. This means that the classification systems can evolve, and what is considered accurate today might be revised in the future.

Outlines

00:00

🍄 Introduction to Fungi Diversity and Classification

The script begins by highlighting the ubiquity of fungi, which can be found in various environments, including in our homes. It emphasizes the diversity of fungi and how scientists classify them into different phyla based on unique features. The video aims to discuss the major phyla of the kingdom fungi, focusing on recent classification systems rather than older ones. The first phylum introduced is Sky tridiomycota, which contains the simplest and most primitive fungi. These are unicellular organisms typically found in water bodies or wet soils, characterized by their chitin cell walls and saprotrophic or parasitic nutrition. What sets them apart is their production of motile zoospores, which are unique among fungal spores due to their ability to move using a flagellum. A well-known example of a skytrid is the organism called aloe mysis.

05:02

🍞 Zygomycota: The Stale Bread Mold Fungi

The second paragraph delves into the phylum Zygomycota, exemplified by the common bread mold, Rhizopus stolonifer. This fungus reproduces asexually through sporangiospores, which form within a sporangium. However, under unfavorable conditions, zygomycetes switch to sexual reproduction. The sexual reproduction process involves the fusion of compatible haploid hyphae, leading to the formation of a zygospore containing multiple diploid nuclei. This zygospore undergoes meiosis, resulting in haploid spores. The process is termed conjugation, hence zygomycetes are also known as conjugated fungi. The paragraph also touches on the commercial importance of some zygomycetes, such as yeast used in baking, brewing, and winemaking.

10:05

🍄 Ascomycota: The Sac Fungi with Ascus and Ascospores

The third paragraph discusses the phylum Ascomycota, characterized by the presence of an ascus, a sac-like structure containing haploid sexual spores called ascospores. These fungi, also known as sac fungi, reproduce sexually through a process involving plasmogamy, karyogamy, and meiosis, resulting in the formation of ascospores within the ascus. The ascus is housed within a spore-bearing structure called an ascocarp. Ascomycetes are beneficial, especially in commercial applications, with yeast being a prime example used in various food processes. Other examples include truffles, morels, and Aspergillus, which, despite once being classified as a deuteromycete, is now recognized as an ascomycete due to molecular analysis.

🍄 Basidiomycota: The Club Fungi with Basidia

The final paragraph focuses on the phylum Basidiomycota, commonly known as club fungi due to their club-shaped spore-bearing structures called basidia. These basidia are found on the gills of mushrooms, which are part of the fruiting body known as the basidiocarp. Sexual reproduction in basidiomycetes involves the production of basidiospores within the basidia. Unlike other fungi, basidiomycetes primarily reproduce sexually, and the paragraph does not discuss asexual reproduction for this group. The phylum includes various types of fungi such as mushrooms, toadstools, shelf fungi, smuts, and rusts. The script concludes by acknowledging the dynamic nature of fungal classification, hinting at the possibility of further changes in the future.

Keywords

💡Fungi

Fungi are a diverse group of organisms that include mushrooms, molds, and yeasts. They are distinct from plants and animals. In the video's context, fungi are the main theme, with a focus on their widespread distribution and unique characteristics. Examples given include the greenish-black patches on old bread, which is mold, a type of fungi.

💡Classification

Classification is the process of organizing living things into groups based on shared characteristics. The video discusses how fungi classification has evolved over time, with scientists now using more advanced systems. It's crucial for understanding the diversity and relationships among fungi.

💡Phylum

A phylum is a level of classification in biology, ranking above class and below kingdom. The script mentions several phyla within the kingdom of fungi, each with distinct characteristics, illustrating the diversity within the fungi kingdom.

💡Chitin

Chitin is a tough, flexible material found in the cell walls of fungi, providing structural support. The video notes that all fungi have chitin cell walls, which is a key characteristic that sets them apart from plants.

💡Saprotrophic

Saprotrophic refers to an organism that feeds on dead organic matter. The video mentions that many fungi exhibit saprotrophic nutrition, breaking down dead material and recycling nutrients back into the ecosystem.

💡Zoospores

Zoospores are a type of fungal spore that can move on their own, typically through water. The video uses the example of the phylum Chytridiomycota, where zoospores are equipped with a flagellum, allowing them to swim and thus disperse.

💡Zygomycota

Zygomycota is a phylum of fungi that includes molds like Rhizopus stolonifer, commonly known as bread mold. The video explains their sexual reproduction process, which involves the formation of zygospores, highlighting their role in the fungi life cycle.

💡Ascomycetes

Ascomycetes, or sac fungi, are a phylum of fungi that produce sexual spores called ascospores within a sac-like structure called an ascus. The video discusses their importance in commercial applications, such as in baking with yeast.

💡Basidiomycota

Basidiomycota, or club fungi, include mushrooms and toadstools. They are characterized by their club-shaped spore-bearing structures called basidia. The video explains that these fungi typically reproduce sexually, releasing basidiospores from their fruiting bodies.

💡Deuteromycetes

Deuteromycetes, also known as imperfect fungi, are fungi that do not show a sexual phase in their life cycle. The video clarifies that they are not a true phylum but a group of fungi that are more closely related to other phyla.

💡Conjugation

Conjugation is a type of sexual reproduction in fungi where the tips of hyphae fuse to form a zygospore. The video uses zygomycetes as an example, explaining how this process leads to the formation of haploid spores.

Highlights

Fungi are widely distributed and can be found almost everywhere, including inside homes.

Fungi exhibit a high degree of diversity, each with unique features.

Fungi classification has evolved significantly over time.

Scientists now use more advanced systems for classifying fungi.

The phylum Chytridiomycota includes the simplest and most primitive fungi.

Chytrids are often unicellular and found in water bodies or wet soils.

Chytrids produce unique, motile zoospores with flagella.

Zoospores are the only motile fungal spores.

A well-known chytrid is Allomyces.

Zygomycota includes fungi like Rhizopus stolonifer, responsible for bread mold.

Zygomycotes reproduce sexually through a process called conjugation.

The zygospore is a thick-walled structure containing multiple diploid nuclei.

Ascomycetes are characterized by the presence of an ascus, a sac-like structure containing ascospores.

Ascospores are haploid sexual spores produced within the ascus.

Sac fungi, or Ascomycetes, include commercially important species like yeast.

Basidiomycota, or club fungi, are recognized by their club-shaped basidia.

Basidia are found on the gills of mushrooms and produce basidiospores.

Basidiomycetes include mushrooms, toadstools, and other fungi that form fruiting bodies.

Deuteromycetes, or imperfect fungi, do not show a sexual phase in their life cycle.

Deuteromycetes are not considered a true phylum as they are more closely related to other phyla.

Fungi classification is dynamic and subject to change with new research.

Transcripts

what if I tell you that fungi are so

widely distributed on our planet that

you can find them pretty much everywhere

yes really in fact you might not even

have to step out of your house in order

to see one the greenish black patches on

that two-week old bread fungi that

bottle on the kitchen shelf which is

marked activated East fungi the

mushrooms growing on those damp logs in

your garden you know it fungi and you've

probably noticed by now that they're

wildly diverse too each of these fungi

has its own set of unique features and

using these features scientists were

able to classify them over the years but

the thing is that in all this time fungi

classification has changed dramatically

many scientists nowadays refer to newer

more advanced systems of classification

so in this video that's what we're gonna

do as well we're gonna talk about some

of the major phyla in kingdom fungi and

their distinct characteristics and while

we are doing so we'll try to stick to

the more recent versions of fungi

classification rather than the older

ones so let's get into it

the first phylum we have over here is

Sky tridiomycota now I'll be honest I

didn't get that pronunciation right the

first time and neither did I know that

this phylum existed up until I actually

started looking into it and it turns out

that this phylum houses all of the

simplest most primitive fungi to ever

exist on our planet most of these

skytrids that's what you call the

members of this phylum most of this guy

these kitrids are unicellular organisms

that are often found in water bodies or

wet soils and like every other fungi

they also have chitinus cell walls and

Exhibits saprotrophic or parasitic

nutrition however what truly sets

skytrids apart from the rest of the

fungi are there a motile zeuspores the

spores that the kitrids produce they are

called zoos Sports and each of them come

equipped with a flagellum like this and

using this flagellum the Zeus pore can

actively move around or swim around all

on their own and mind you no other

fungal spore can do this they are the

only more tile spores to exist and

kitrids are the ones that can produce

these pores a very famous example or a

very famous kitrid is this organism

right here which is called aloe

my sis

next up we have the zygomyces members of

the phylum zygomycota and we've already

come across a zygomycin before remember

the stale moldy bread at the beginning

of this video well the fungus that grows

on stale bread it's called the common

bread mold and that is scientifically

called rhizopus tolonifer which is this

fungus right over here so if you take a

piece of that moldy bread and place it

under a microscope this is what you're

gonna see now the most fascinating thing

about zygomycetes is how they reproduce

sexually normally they reproduce

asexually with the help of something

called sporangiospores which are these

pores that are formed inside a structure

called a sporangium you can actually see

a sporangium right over here so this

bulb-like structure here this is the

sporangium

sporangium and inside of this is where

the sporangiospores are formed and

sporangiospores are the way to go

normally when things are fine but when

the environmental conditions become

unfavorable the fungus or these fungi

they resort to sexual reproduction that

is when sexual reproduction takes place

so let's take a look at this process so

during sexual reproduction what really

happens is that two compatible haploid

hyphae will start extending towards each

other till their tips touch kind of like

this and the minute the tip touches what

happens is that it kind of walls off a

section or a portion of this tip so

let's say it starts to wall off

somewhere here by building by forming

something called a septum which you can

think of it like a partition so this is

a septum

I'll just write it down over here so it

starts to wall off a certain section by

forming this septum and when this once

this partition is done or this Walling

off is done what will happen is that

everything in this portion right over

here will fuse together even the nuclei

now over here I have you can see that

there are only two two nuclei but

usually what happens like this is just

an image that I've drawn but uh in real

life like in nature when this fusing

happens there are many haploid nuclei

which are present in this area depending

on where this wall of thing happens

where the partition begins to appear So

based on where the partition appears

many haploid nuclei are present in

between or they are trapped in between

this uh section of the extension or the

tips basically so now what happens these

nuclei they will also fuse along with

the tips so after all of the fusion what

really happens what we get at the end of

that is this zygospore so this uh

haploid nuclei will fuse with this

haploid nuclei and give us this purple

one and again the same thing happens

with these two nuclei and we have two

basically uh diploid nuclei because the

haploid nuclei diffused right

so in the end we finally have a

zygospore which contains multiple

diploid nuclei now what happens after

this this zygospore will eventually

undergo meiosis and because of meiosis

What will happen this diploid nuclei

will become haploid nuclei

because of the meiosis that it happens

and each of these haploid nuclei each of

them separately will become a haploid

Spore and that is how uh through sexual

reproduction these haploid sexual spores

are formed

now this type of sexual reproduction

where the tips of the hyphy fuse

together to give the zygospore which

eventually gives us a haploid spores

this entire process is called

conjugation

and because of this because of this

conjugation process

zygomyces are often referred to as

conjugated fungi moving on the third

phylum on our list is ascomycota these

fungi are characterized by the presence

of something called acai or an Asus and

ascus is a sac-like structure which

contains the haploid sexual spores

called ascospores so these bead-like

structures that you can see inside this

sac-like thingy so these are the

ascospores inside the ascus and because

of the sac-like structure these fungi

are also called Sac fungi during sexual

reproduction

ascospores are formed inside thousands

of acai which in turn are found inside

of a Spore bearing structure called an

ASCO ascocarp now this so basically what

happens these ASCO spores they are

formed inside this ascus or inside the

acai and these acai is in turn found

inside something called the Asco

carp which is a Spore bearing structure

so inside this you will find the acai

and inside the acai you will find the

ASCO spores now the process of sexual

reproduction goes something like this

plasmogamy or Fusion of cytoplasm takes

place between two compatible haploid

cells and the fused cell enters a

diaryotic stage where the nuclei the

haploid nuclei they remain free

eventually these nuclei will also fuse

that means kariogami will take take

place and we will end up with a diploid

zygote inside the ascus this zygote will

further undergo meiosis and that will

give us the haploid ascospores these

ASCO spores are then released into the

environment and they end up germinating

at suitable places as for my seats also

undergo asexual reproduction by

producing asexual spores called kunidia

ascomyces are incredibly helpful to us

as well especially commercially and a

very important example of that is East

remember how we talked about uh dry

activated yeast being something that we

can find in our kitchen so we use East

to East in a variety of different things

like baking Brewing fermenting wine and

a bunch of different things so East is

an ascomycet which is extremely

important to us other examples of

ascomyces include truffles

uh then there are morals now these are

treated as Delicacies uh in different

parts of the world then there's also

aspergillus which is something you might

have heard of uh which is also uh an

ascomycet so these are some examples of

ascomyces the next major phylum is that

of the mushrooms AKA phylum basidio

mycota bacidio my seeds are easily

recognized by their club-shaped Spore

bearing structures called basedia now

there's only one structure here so this

will be a basidium that's the singular

form and because of this club shaped

basidium or basidia these uh fungi are

also called Club fungi now where will

you find this basidium or where will you

find all the biseria you will find them

on the gills of the mushroom so these

lines that you can see these are the

gills of the mushroom which are found on

the underside of the cap and this whole

protruding thing with the cap and

everything that is the fruiting body of

the mushroom called the basidio carp so

this entire thing let's pick a different

color we can't really see it in here so

this entire thing the protruding part of

the mushroom which is you know on the

top of the soil that we can see this is

the fruiting body which is called The

Busy do

carp

so that means the basidio carp Bears the

basidia on the gills now inside each

basidium beside your spores which are

these sexual spores by the way they are

produced and these basidio spores they

are produced in it's very similar to how

the ascospores are produced now once

these haploid basidio spores they are

formed they will be released into the

environment from the basidios carp and

then they will germinate into new fungi

now remember all mushrooms toadstools uh

then shelf fungi then smarts and rusts

all these types of fungi they belong to

phylum basidio mycota so they're all

basidiomyces now if you're wondering why

I didn't mention an asexual reproduction

here that's because usually all basidio

my seeds reproduce sexually so that's

why we are not discussing about the

asexual reproduction here

now these are just some of the major

phyla which has been included in kingdom

fungi now that that doesn't mean that

these are the only phyla by the way

there are other different phyla as well

for example glomeromycota is one such

phylum which is there in kingdom fungi

but one that we didn't really discuss

here uh this includes fungi which live

in very close association with uh plant

roots there's another group that you

might have heard of called

deuteromycetes aka the imperfect fungi

you know the fungi that do not show a

sexual phase in their reproductive

Cycles at all so those are the

deuteronomyces but the thing is that

deuteronomycota is not considered to be

a true phylum why because their members

are more close to closely related to

organisms from other phyla than each

other let me explain this to you with an

example aspergillus was earlier thought

to be a Deuter my seat but after a lot

of research and a lot of studies and

molecular analysis they finally found

out that aspergillus is more closely

related to ascomyces rather than

deuteronomyces so that's a completely

different phylum right ascomycota in

fact we we literally wrote down

aspergillus in the lesson today under

ascomycota so that's how aspergillus was

moved from deuteromycota to ascomycota

and that is why ASCO um that is why

deuteronomycota or deuteronomyces they

are not considered to be a true uh a

true member or a true phylum for that

matter so you see fungi classification

is an ever-changing Ever improving

ordeal it's not set in stone who knows

that maybe a few decades from now will

have a completely new system of

classification for all of these fungi it

is that dynamic