Life sciences
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Study unit 1
Taxonomy: Life's Filing System – Crash Course Biology #19
https://www.youtube.com/watch?v=F38BmgPcZ_I
It is human nature to sort a large group of objects into smaller units – each group with common
form, function or characteristics. Just think about when you buy groceries – you are going to search
for full cream milk at the rest of the types of milk (low fat milk, ultra-pasteurised milk, etc.), which
will again be sorted together with the other dairy products (butter, yogurt, etc.).
Likewise do microbiologists, zoologists and botanists also place the large variety of organisms that
were created on earth into groups – thus, they classify the organisms with common characteristics in
particular units. This science, which deals with the classification of organisms, is known as
taxonomy.
As a future Life Sciences teacher (LScT) you should in the first instance have insight into the relevant
theory regarding the classification of animals / organisms and secondly you must be able to teach it
in an effective way to the learners.
Taxonomy is the science of classifying living things
Every living thing/organism is related to every other living thing, meaning if we go far back well see
that we all have a common ancestor (an organism that we descended from)
What is the trick of taxonomy?
It is basically figuring out where all those branches of the evolutionary tree are, and finding some
convenient labels to help us understand all of these remarkable interrelationships
Taxonomy isn’t about describing life and all of its ridiculous details then what is it about?
it about helping humans understand it, because it is way too complicated without structure
so to get that structure biologists use the taxonomic system to classify all the organisms on the
earth, it is sometimes called the Phylogenetic Tree/ The Tree of life
Phylogenetic Tree illustrates the evolutionary relationships between all the living species
Biolo-graphy
Carl Linnaeus was a Swede born in 1707
And early in his career as a Botanist he realized that the botanical nomenclature of 18th century
Europe was “just crap” for instance in his normal day, the “Formal” name of a tomato plant was
Solanum caule inerme herbaceo foliis pinnatis incisis
Linnaeus actually said once, “I shudder at the sight of the most botanical names given by modern
authorities”
Back then people grouped organisms by analogous or homoplastic traits, structures that appear
similar but actually come from completely independent origins NB by this definition birds will be
more closely related to butterflies than to reptiles because birds and butterflies can both fly
Linnaeus chose homologous traits for his classification system
Traits that stem from a common evolutionary ancestor
NB New Texa above Linnaeus Kingdom is Domain it as broad as you can get
The Domains are Bacteria, Archaea and Eukarya
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Bacteria and Archaea are prokaryotes, meaning that their genetic material goes commando
with no nucleus to enclose it
While Eukarya makes up all life forms with a nucleus and include all the life that you think of
as life, and quite a lot of the life you don’t think about at all
It might seem like, since all macroscopic life only gets one domain, it’s kinda silly to give
prokaryotes two and for a long we didn’t divide them into different domains they hand out
together in a single domain called Monera
But it later became clear that Bacteria, which live pretty much everywhere on earth,
Including inside of us and deep in the earth’s crust
and Archaea which are even more hardy bacteria, have distinct evolutionary histories
Archaea being more closely related to eukaryotes and yes, thus me and you
They have totally different cell membranes and the enzymes that they use to make RNA
polymerase, is much more like ours..
Under the domain Eukarya which is by far the most interesting and even occasionally adorable
domain, we have kingdoms: Protista, Plantae, Fungi, Animalia
These are categories that are human creation, but there are good reasons for that human creation
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The unscientific truth is that we looked at life and divided it up based on what we saw. So
we were like, well protists are single-celled organisms, so, they’re very different from the
rest of the domain
And plants get their energy from the sun and
fungi look and act very different from plants animals, and we already know what animals are
so they have to get their own Kingdom
Plants or plantae are the autotrophs of the Domain Eukarya
Autotrophs meaning that they can feed themselves, through photosynthesis (the presence
of sunlight)
Their cellulose-based cell walls and Chloroplasts giving them a distinct difference from all
other multi-cellular life
Though there are two other sorts of -trophs
There’s a heterotrophs, which get their energy by eating other organisms
Then there’s Chemotrophs, which are weird and crazy and only show up in Bacteria and
Archaea and they get their energy from chemicals
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Now
Now the Kingdom Protista is crazy because it contains both Autotrophs and heterotrophs
this simply mean some Protists can Photosynthesize while others eat living things
Protists are basically a bunch of weird, eukaryotic single-celled organisms that may or may
not be evolutionarily related to each other
Some are plants like, like Algae
Some are more animal like, like amoebas,
And some are fungus like, like slime molds
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Fungi
The funguses
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Animalia
These include mushrooms, smuts, puffballs, truffles, molds, and yeasts
And they’re cool because they have cell walls like plants, but instead of being made of
cellulose,
They’re made of another carbohydrate called chitin,
Because fungi are heterotrophs like animals, they have these sorts of digestive
enzymes that break down their food and get re absorbed
but they can’t move so they don’t require a stomach for digestion
They just grow on top of whatever it is they’re digesting and digest it right where it is
Kingdom that we find ourselves and 100% of adorable organisms in
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Animals are multicellular, always
We’re heterotrophic, so we spend a lot of our time hunting down food because we can’t
make it ourselves
And almost all of us can move
And most of us develop either two or three germ layers during embryonic development,
Except for Sponge
So we use this taxonomic system to describe the common ancestry and evolutionary history of an
organism
Looking at the phylogenetic tree you can tell that humans are more closely related to mice
and than we are to fish, and more closely related to fish than we are to fruit flies
ACTIVITY
1.2.1
Name, discuss and compare the different classification systems of life on earth
Artificial system of classification.
Artificial system of classification is based on one or a few superficial resemblances. For example,
animals are classified as aquatic (water-dwellers), terrestrial (land-dwellers) and aerial (air-dwellers)
according to habitat, as carnivores (flesh-eaters) and herbivores (plant eater) according to the mode
of feeding, as oviparous (egg-layers) and viviparous (young-producers) according to the mode of
breeding, etc. Similarly, plants are classified as herbs, shrubs, and trees based on their habit
Natural system of classification
Natural system of classification is based on a number of structural and morphological taxonomic
characters.
phylogenetic system of classification.
The classification of organism based on their evolutionary interrelationships is called phylogenetic
classification.
1.2.2 Theories of life……
1.2.3 Distinguish between the following terms with suitable examples: systematics, taxonomy,
classification, phylogeny, species, and taxon.
A. Systematics
Is the study of biodiversity, how does it help us? It helps us understand the evolutionary
relationships between species
What is used for?
In systematics traits of living and fossil organisms are used to infer the relationships among
organisms’ overtime
OR
It is used to infer relationships among living and fossil organism’s overtime
To Infer is to decide that something is true
B. Taxonomy
Taxonomy is whereby we organise biodiversity or species
So, In taxonomy species are identified, named and organised into related categories
C. Taxon
Is a general name for an organism
D. Classification
is the process of naming and assigning group of organisms to a taxon
E. Taxonomists
Scientists who study taxonomy and strive to classify all life on earth
who is the father of modern taxonomy?
Carl Linnean
F. Phylogeny
the history of the evolution of a species or group, especially in reference to lines of descent and
relationships among broad groups of organisms.
G. Species
group of living organisms consisting of similar individuals capable of exchanging genes or
interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and
denoted by a Latin binomial, e.g., Homo sapiens
1.2.4
Use the different taxa to classify Amoeba proteus
1.2.5
Discuss the different characteristics that may be used to classify organisms.
1.2.6 What do you understand by the binominal nomenclature and explain the implications it
holds for you as Life Scientist.
1.2.7 Study the phylogenetic tree, Figure 19.4 on p. 341 in Mader and Windelspecht and explain
what you understand by it.
1.2.8
Setting of a phylogenetic tree will be covered during a contact session.
Dichotomous (binary) keys
A dichotomous key is a tool compiled by taxonomists to enable a person to determine to which
group a plant or animal belongs, or to ascertain the name of the organism.
The prefix “di” in the name refers to the fact that two characteristics are contrasted against one
another every time. A choice must be made between these two contrasting characteristics until the
name or group name for the organism has been established. Dichotomous keys therefore offer an
easy and simple tool to identify organisms.
Take note of the requirements set for each paired statement in Figure 2:
It must contrast with each other and exclude the other group.
The characteristics that are applied must be observable; it may be qualitative, e.g., the shape of an
abdomen or it may be quantitative, e.g., the number of hair or the length of a stalk.
For a particular species this characteristic must be a constant characteristic and should not vary due
to environmental influences.
STUDY UNIT 2
PROTIST
The kingdom Protista represents a diverse group of organisms –from plant-like, fungus-like to
animal-like. In this module we study the animal-like Protista which are either free-living
heterotrophs ingesting food or parasites. Protists represents the oldest branch of eukaryotes in the
tree of life. Many protists serve as model organisms critical to many areas of scientific research,
including ecosystem ecology, medicine, and epidemiology. Protists are also at the base of many
food chains, serving as the foundation for all life in an ecosystem.
2.2 General characteristics of the protozoa
Characteristics of Protists
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mostly unicellular, some are multicellular (algae)
can be heterotrophic or autotrophic
most live in water (though some live in moist soil or even the human body)
ALL are eukaryotic (have a nucleus)
a protist is any organism that is not a plant, animal, or fungus
Classification of protists
how they obtain nutrition
how they move
Plant-like protists – also called algae – autotrophs
Fungus-like protists – heterotrophs, decomposers, external digestion
Animal-like protists – also called protozoa (means “first animal”) – heterotrophs
2.3 The taxa of Protozoa
NOTE: The current system of classification for eukaryotes has been changed. In
2005, based on new phylogenetic data the kingdom Protista was split into five
supergroups. At this stage, we will still study the protist group as a Kingdom, but be
prepared that it might change in future, another reminder of the dynamic nature of
taxonomy.
Four phyla of animal-like protists – Classified according to how they move
Zooflagellates – flagella
Sarcodines – pseudopodia (extensions of cytoplasm)
Ciliates – cilia
Apicomplexans / Sporozoans – do not move around