Transcript 4.1 Structure and Replication of the Genetic Material

1.1 Biodiversity
Biodiversity
There are 3 levels of diversity:
Genetic diversity
Species diversity
Ecosystem diversity
Genetic diversity
• The sum of alleles present in a particular
species represents their genetic diversity
• Genetic diversity allows populations to
adapt to changing environmental conditions
– This makes the species as a whole more likely
to survive and/or evolve over time
Genetic diversity
• Some modern practices, such as growing
monocultures, put species success at risk
because it decreases genetic diversity
– This practice makes a species more susceptible
to disease and pests
– Scientists often look for genes in wild
populations of the same species to boost
immunity or resistance and increase genetic
diversity in genetically uniform crops
Species Diversity
• The variety and relative abundance
(biomass) of species in a given area
• Generally ecosystems with lots of species
diversity are more productive and have a
higher tolerance for stress and changes than
those with lower diversity
Ecosystem Diversity
• A wide range of habitats, a wide variety of
organisms and the relationships that connect
them determine how successful an
ecosystem will be
• Changes to one part of an ecosystem can
vary from some effect to a profound effect
on the health and sustainability of the
system as a whole (e.g. keystone species)
Valuing Biodiversity
• Biodiversity provides ecosystem services
that benefits all organisms including
humans:
– Medicines, agriculture, decomposition of toxic
substances etc. benefit humans
– Pollinator services for plants
– Nutrients cycle through the different spheres
– Modification and maintenance of the
enviroment
Honeybee crisis
• Why are honeybees important?
• Before humans imported the European
honeybee to North America (1800s) there
were over 4000 different pollinators. Now
there are very few.
• What happened?
– Consider the three levels of diversity in your
answer.
1.2 The Science of Classification
Renaissance
• Era of “rebirth”, exploration from Europe
begins
• Interest shifted from the Divine to the
human form
• Interest in human physiology and function,
disease
• Era of experimentation, observation and
analysis begins
William Harvey
• 1578-1658
• Discovered the
circulation of the
blood
• Part of the trend to
looking for natural
causes and cures for
diseases
• The beginning of modern
medical practice
• Doctors
– replaced village “wise
women” so they needed to
make medicines
– Required a reliable way of
identifying medically
important plants
• Beginning of the study of
Botany
Herbals
• Related species of plants
do not look the same in all
habitats
• Within the same related
group some can be
beneficial, others
poisonous
• Invention of the printing
press allowed mass
publication of accurate
diagrams and descriptions
Modern Taxonomy
• Factors that contributed to modern
taxonomy
– Global European exploration brought many
new species to Europe
– No system for naming new or existing
organisms was in place
• The same plant or animal could have different
names even in the same language
Linneaus (1707-1778)
• Born Carl von Linné
(Swedish)
• Father of modern
taxonomy
• Greatly influenced by
Aristotle’s concepts of
fixed genus and species
• Major work – Systema
Naturae
Systema Naturae
• Hierarchical levels beginning with
Kingdom (Plantae and Animalae)
• Each kingdom divided into Classes, each
Class into Orders, Genera, and Species
– Not classes in the modern sense – created by
God
• Binomial nomenclature
– Each organism has a unique genus and species
Systema Naturae
• Plants were classified according their
method of reproduction
– A brilliant guess!
• Used Latin (and Greek) so that the method
was international
Systema Naturae
• Limitations
– Only physical features (morphology) could be
used for classification
– Function or behaviour could not be used for
classification purposes
Modern Taxonomy
• Linneaus’ system is still the basis for
modern taxonomy
• Added Phylum between Kingdom and
Class, and Family between Order and
Genus
• Still use Latin although many new species
use words with other language roots
Modern Taxonomy
• Genus is always capitalized, species in
lower case
• Genus and species are written in italics
(print) or underlined (handwritten)
• When used for the second time in a
document the genus name is often
abbreviated to the first letter
– E.g. Homo sapiens becomes H. sapiens
Two Kingdoms
PLANTS
ANIMALS
Three Kingdoms
ANIMALS
PLANTS
PROTISTS
Five Kingdoms
Six Kingdoms – 3 Domains
Animalia
Plantae
Protista
Eukaryotic cells
Eubacteria
Archeabacteria
Prokaryotic cells
Fungi
Domains
• Domains are the broadest taxon in use
• There are currently three domains
– Archaea
• The oldest forms of life, prokaryotic, many were
anaerobic and contain extremophiles
– Bacteria
• Also prokaryotic
– Eukarya
• All eukaryotic organisms
Modern taxonomy
• Linneaus grouped species according to
morphology – appearance
• Now scientists have access to DNA analysis
and phylogeny to help with classification
– Phylogenetic trees are useful in showing
relationships over time and divergence from a
common ancestor
Cladistics
• A particular method of hypothesizing
relationships among organisms. Like other
methods, it has its own set of assumptions,
procedures, and limitations.
• The best method available for phylogenetic
analysis, it provides an explicit and testable
hypothesis of organism relationships.
Cladistics
• There are three basic assumptions in
cladistics:
1. Any group of organisms are related by
descent from a common ancestor.
2. There is a bifurcating pattern of
cladogenesis.
3. Change in characteristics occurs in lineages
over time.
Phylogenetic tree(s)
Each node
represents a
point where a
major
divergence in
characteristics
occurred
Tree of Life
Levels of Classification
Least specific
Most specific
Kingdom
Phylum
Class
Order
Family
Genus
Species
Mnemonic
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King
Phyllip’s
Class
Orders
Family
Geni to
Speak
Binomial Nomenclature
• Or a two part naming system
• Commonly referred to as the ‘scientific
name’ of an organism
• Each species is unique (review definition!)
• Related species are grouped together into
the same genus
• Related genera (plural of genus) form
families
Binomial Nomenclature
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Related families are grouped into orders
Orders are grouped into classes
Different classes form a phylum
Different phyla (plural of phylum) form a
kingdom
Panthera pardus
The genus and species
names are always written
in italics (or underlined if
hand written) and the
genus name is capitalized.
The first time the genus name is used
it is written out in full, afterwards it
can be abbreviated to a capital letter,
for example P. pardus or P. leo.
pardus
Panthera
Felidae
Carnivora
Mammalia
Chordata
Animalia
Binomial Nomenclature
• The term taxon (plural is taxa) refers to a
level in the hierarchy
• The Insecta are such a large group that
superfamillies and suborders are used as
well
Dichotomous Keys
• Method used to create identification keys
based on pairs of characteristics
• Only morphology (observable
characteristics) can be used – no behviour
or function can be used
• Structured format to the keys
• Two types – spider and standard formats
Spider Key
2a
1a
yes
Large claws
present
yes
Has five or more
distinct appendages
no
yes
Shaped like a star
2b
no
3a
no
3b
1b
Standard format key
1a. Has five or more distinct appendages ……… 2
2a. Has large claws …………………………. lobster
2b. Does not have claws ……………………. 3
3a. Shaped like a star ………………….. starfish
3b. Not star shaped ……………………. octopus
1b. Has less than five distinct appendages……… whale
Notes on Keys
• Use an “a” and “b” for each level
• Start at the margin and indent for each new level
– Keep levels even no matter what the number is, it is the
number of criteria that matter
– Split numbers as needed so that each identification can
follow through without changing branches
• Use dots to fill the space to the right margin where
either a number or item appear
Standard format key
1a. Has five or more distinct appendages ………… 2
1b. Has less than five distinct appendages……….. whale
2a. Has large claws ………………………….…... lobster
2b. Does not have claws …………………………. 3
3a. Shaped like a star ……………………………. starfish
3b. Not star shaped ………………………………. octopus
Notes to key
• Pairs of related criteria appear together
• Single space between each number
• Use dots to fill the space between the
criteria and the right margin where either a
number or item appear
Dichotomous
Key
The prefix “di” means 2 so there are two
characteristics to consider in each choice or step of the
key. Each characteristic must be chosen so that there
is a ‘yes’ or ‘no’ answer. There cannot be ambiguity
or a possible 3rd choice.
The answer will determine which step is next in the
process