Download Bio 20 Unit B part 2

Diversity, Adaptation and
Change in Ecosystems
Biodiversity and Classification
• Scientists estimate that there are between 2 and
4.5 million different types of organisms on the
planet. Likely there are / were many more. To
organize, name and group these organisms
based on similar characteristics, scientists use a
system called taxonomy.
• Taxonomy – the science of classification
according to presumed relationships
among organisms.
• Scientists use a hierarchical system, where
organisms are classified in a series of
smaller groups.
Hierarchical System
Most • Domain- Bacteria, Eukarya, Archea
General • Kingdom – Monera, Protista, Plantae,
Most
Specific
•
•
•
•
•
•
Fungi, Animalia
Phylum – sub-groups of each kingdom
Class
Order
Family
Genus
Species – organisms that are very similar
and can naturally interbreed to produce
fertile offspring
Binomial Nomenclature
• When organisms are assigned a scientific name,
the name is given in two parts, Genus species,
and the name is either written in italics or
underlined. This system is called binomial
nomenclature.
• Genus name indicates organisms that are
similar, and is always capitalized.
• Species name indicates organisms that are
•
different, and is written in lower case.
Ex. Canis lupis
wolf
Canis domesticus
dog
The 5 Kingdoms
• Prokaryotae – includes the bacteria
•
•
•
•
(eubacteria and archaebacteria (unicellular with
no cell nucleus)
Protista – includes single celled plants and
animals and algae (unicellular with a nucleus)
Fungi – includes the mushrooms, yeasts,
moulds (multicellular, decomposers)
Plantae – includes the trees, flowers, mosses
and ferns (multicellular, photosynthesizers)
Animalia – includes sponges, worms,
crustaceans, insects, and mammals (multicellular
and heterotrophic)
• Naming some 2 – 5
•
million organisms
presents a challenge to
scientists. To overcome
this challenge,
dichotomous keys are
used to identify and
classify organisms based
on their characteristics.
Dichotomous Key
• Scientists today believe
that organisms changed
over time.
Phylogeny
• the history of
evolution of a
species or group
of organisms.
This history, and
the evolutionary
relationships
between
organisms is often
shown in a
phylogenetic tree.
Evolution
The theory that changes
occur and can been seen in
the inherited traits of a
population from 1
generation to another
Evidence of Evolution – Fossils
Paleontology (the study of fossils) has provided
scientists with an historical record of organisms
that once lived. Fossil evidence has also
revealed a number of patterns:
1. In the past, the earth was home to species that
are very different from those that exist today.
2. The complexity of living organisms seems to
have increased from the past to the present in a
systematic manner.
3. Living species and their fossil matches are found
in the same geographical regions.
Dating the Past
• Radioactive elements lose particles (and mass)
as they decay at a constant rate (despite
temperature, moisture or pressure). Radioactive
decay can be used as an accurate a measure of
the age of an object. The half-life of an object
is the length of time it takes for half the sample
to decay and become stable. By measuring the
age of rock in which fossils are found,
paleontologists can estimate the age of the
fossils, creating a chronological evolutionary
scale.
Biogeography
• Biogeography studies the distribution of different
•
•
organisms on the surface of the earth. Over
long periods of time, the Earth’s continents have
shifted position, re-distributing living organisms.
The continents can be matched up
geographically and biologically. Some islands
are far away from land and host a unique set of
organisms. The evolutionary pressures and past
of these isolated organisms can also be studied.
Essentials of Geology : Chapter 2 : Animations
Example: Pangea and the idea that similar
organisms exist on 2 different continents (Bison
in Northern Canada and Bison in Russia)
Anatomical Evidence
• Scientists can study similarities and
differences in the anatomy of organisms
and in their embryological development
to determine ancestral links between
organisms.
Homologous structures
- features with similar
structures, and different
functions that indicate an
evolutionary relationship
between organisms.
- Shows evolution from a
common ancestor
Ex. bat wing and human
hand
Ex. dolphin flipper and
forelimb of a dog
Analogous structures
– features with similar
functions, but very
different structures
that indicate there is
little evolutionary link
between organisms.
-Shows no common
ancestor
Ex. bat wing and
butterfly wing
Vestigial features
• rudimentary structures that have no clear
•
function that may have once been important,
but are evolving out of existence.
Ex. Appendix & tailbone of humans, small foot
found on some snakes
Biochemical Evidence
• Scientists believe that the amino acid
sequences in proteins or related organisms are
more similar than those in unrelated organisms.
DNA sequences that make up different genes
control the traits an organism will have. More
similar organisms will have more similar DNA.
– Ex. Monkeys and humans share about 94% of the
same genetic information and about 90% of the same
amino acids.
• Other examples are: waste products
(nitrogenous waste), hormones, chromosomes
Theories of Evolution
Lamarck –Inheritance of Acquired
Characteristics
• Lamark believed that organisms would
desire to evolve and develop a certain
trait that they required within a life
time to survive and would lose unnecessary traits (‘Use-Disuse’ Theory).
He also suggested that these traits
could be passed down to offspring
(Inheritance). Ex. if a giraffe needed
along neck to reach food, the long
neck would evolve as the giraffes
spent many generations reaching for
food.
Giraffe Evolution
Darwin – Natural Selection,
Survival of the Fittest
• Darwin believed that there were many
variations among organisms. Traits that
were better adapted to survival and
reproductive success, would be passed
down to future generations (Inheritance).
Darwin’s theory required that:
Darwin’s theory required that:
1. Variations exist among organisms.
2. In a changing environment, specific
variations were better adapted to
survival than others.
3. Only those organisms that survive (and
have the adaptive traits) will sexually
reproduce. ‘Survival of the Fittest’
4. The adaptive traits will be passed down
to the offspring.
5. **Natural Selection always occurs,
each trait has a chance to be passed on,
but its likely the better trait would be
passed
Sources of Variation
• Mutations – are random changes in the DNA
sequence of a chromosome. Mutations may be:
– neutral – have no effect on an individual
– harmful – hinder survival or reproductive success
(selected against and may disappear)
– beneficial – improve survival or reproductive success
(selected for and accumulate)
• Example: Bacteria mutating to become resistant to
drugs like antibiotics.
– Most biological diversity in organisms is due to
mutations
• Sexual Reproduction – involves the
production of an organism from two different
parents. The offspring inherits ½ the genetic
characteristics of both parents, increasing
variability.
– Each parent has two (different) copies of each
gene, but only passes one copy to the
offspring.
– The copy that is inherited by the offspring is
randomly determined.
– Sexually reproducing organisms choose
different mates giving rise to many different
possible combinations (variation).
– Sexual reproduction usually removes/masks
abnormal/faulty genes
• Asexual Reproduction – involves the
production of an individual from one
parent. The offspring is genetically
identical to the parent.
• Example: Cloning
– Cloning decreases genetic diversity/variation
and could possibly cause an unstable
population.
Speciation and Evolution
• Speciation is the formation of a new species. It can
occur by a step by step process known as allopatric
speciation.
1. A physical barrier separates a population into two
isolated groups.
2. Environmental pressures on the two groups are
very different causing the populations to evolve
independently.
3. Over time the accumulated differences between
populations become so extreme, the populations can no
longer interbreed to produce fertile offspring.
(They are two different species).
Tutorial 24.1 Speciation Mechanisms
• Theory of gradualism –speciation takes
place very slowly. Due to Natural selection
• Theory of punctuated equilibrium –
species evolve in bursts very rapidly,
followed by longer periods of stability
(little change). Again, due to natural
selection
• Divergent evolution – the evolution
into many different species.
– Due to different environmental
pressures
– Usually due to a barrier:
• Physical: island
formation/wall/mountain/etc
• Biological:pheromones/enemies
• Convergent evolution – the
development of similar appearance,
structure or behaviors in unrelated
species due to similar environmental
pressures.