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Model 3 Biological Diversity
1. Selection pressures on organism in ecosystems
Key concepts to understand; Favourable characteristics ( adaptations) Evolution by natural selection
Definitions Specie diversity The number of different species and the abundance of each species in
an ecosystem
Ecosystem Any area that contains a community Other living things That interact
with each other and their environments. Ecosystems can be described in terms of The specie they contain
Selection pressures
A combination Abiotic And biotic Factors As well as human activity
Abundance; The number of individuals per Specie In a specific Area At a specific
time
Selection pressures in an ecosystem
Biotic Factors The living Components Or biological features of an environment, Including animals, Plants and microorganisms
abiotic factors The nonliving components of an environment (physical and chemical features)
o Seasonal availability and abundance of food
o The number of competitors o The number of mates available o The number of predators o The number and variety of disease
causing organism
o Temperature à Enzymes in cell o Light availability o Water o Availability of gases ( oxygen and carbon
dioxide) o Soil type o Exposure to natural forces ( wind, tide,
waves)
Inquiry question; How do environmental pressures promote a change in species diversity and abundance?
- Species diversity - Selection pressures à climate, space to live, disease, compotation for food, human
impact, human activity ( e.g pollution and land clearing ) - Ecosystems
Model 3 Biological Diversity
2. Investigation changes in a population of organisms due to selection pressures over time
Organism Change in Abundance and distribution
Selection pressures- change
Cane Toads o Abundance has increases as
they have no predators to kill them
o Destruction; they were introduced from Hawaii in 1935
o Due to having no predators and
natural diseases. The cane toad has become a pest in Aus
o No successful selection pressure o Companion with themselves so
they eat each other
Prickly pears o Introduced in 1800s o Adapted quickly – au’s
diverse environment and dry environment
o No predators o Cactoblastis moth ( biotic
pressure reduced numbers)
3. Conduct practical investigation, and structural, behavioural and physical adaptations
An adaptation may be:
Structural – shape and size of an organism and it’s various body parts eg. kangaroo’s powerful
leg muscles assist it in hopping at high speeds
Physiological – relating to the way the organism functions, how it’s body works eg. human
sweating which assists in heat loss
Behavioural – how an organism responds to its environment eg. penguins huddling together
to stay warm
Inquiry question; how do adaptations increase the organism's ability to survive - Population - Habitat - adaptations
Model 3 Biological Diversity
Results to the experiment below
Leafe Structural adaptation How this aids survival Hakea plant o Waxy coating on upper
surface o Hair on lower surface
o Waxy coating proviants water loss from the STONE MATES on the upper leafed surface
o Hairs on the underside of the leaf prevents water loss, water vapour is trapped in the hairs and creates a hummed environment
Elephant ear
o Large flat leaf ( SA) o Dark green
o Large surface area o Lives in shard ( low light)
needs to capture as much light for photosynthesis
o Dark green – more chorofill in there chloroplast
Eucalyptus
o Waxy coating o Pail colour
o Waxy coating – SONE MATS
o Pale colour to reflect the heat therefore there is less evaporation of water ( less water loss)
Practical : Observation of Structural Adaptations in Plants
Aim
To observe macroscopic structural adaptations of the leaves of five plants and relate these to
increased chances of survival.
Equipment
Disposable gloves
Forceps
Binocular microscope
Camera
Leaf samples of Australian schlerophyll plants such as Hakea, eucalypt, wattles and succulents.
Model 3 Biological Diversity
Risk Assessment
What is the risk? Why is it a risk? How can we minimise the risk?
Plant irritants
Can cause an allergic response Were gloves or wash hands
Plant thorns
Cuts skin and can lead to infection Use forceps to hanndel plant
Method
1. Collect 5 leaves and carefully observe each sample.
2. Place each leaf in turn under the binocular microscope to view structures more closely
3. Record any adaptations that enable the plant to conserve water/obtain light/maintain
temperature
4. Draw or take a photo of each leaf. Label the specific adaptations observed.
5. Construct a table in the space below to include the name of plant, natural environment,
structural adaptation and how each adaptation assists in the plant’s survival.
4. Darwin’s observation and data supporting the theory of evolution by natural selection
The theory of natural selection (Darwin)
1. In any population there are VARITATION between the individuals. More offspring are produced than are needed and there is a constant struggle for survival
2. Those individuals with FAVOURABLE CHARCTERISITICS (ADAPTATIONS) are selected by the environment to survive and reproduce. Those without favourable characteristic are removed from the population
3. The individuals with favourable characteristics REPRODUCE and pass on these
favourable characteristic to their offspring
4. Over time these favourable characteristics become MORE COMMON in the population
Model 3 Biological Diversity Finches - The Galapagos islands
è Finches on the island shows Distinctive
characteristics à beak structure è Only a few finches migrated to the island AND
that each of the different finches had EVOLVED from a COMMON ACESTORS.
è Evolved different beak structures to make use of the different food source’s on the island.
Australian Flora and Fauna
Darwin Noticed è Platypus are similar to water rats in England è Magpies and crows are similar to jackdaws in England è Potoroos ( rat kangaroos) are similar to rabbits
è unrelated animals- living in the same environment
• shared similar adaptation • meaning environment pressures play a large role • selecting those that survive.
5. Modern day examples that demonstrate change
Cane toads – describe in Dawns theory of evolution
è Invasion on new territory from 10-15km per year è Faster hopping style è Cane toads witch had a favourable characteristic – survived è Those reproduced- passing on to the offspring è This became more common
Antibiotic resistant strains of bacteria
è Vernation in bacteria, same resistant to anti- biotic è Resistant bacteria with favourable characteristic survive, non- resistant bacteria die è Resistant bacteria reproduce pass on resistance to offspring è Resistant in bacteria are more common
Model 3 Biological Diversity
6. Explaining biological diversity in terms of the theory of evolution
Biological diversity or biodiversity refers to the variety of life forms on earth • Diversity of characteristics • Variety of ecosystems they inhabit
We depend on biodiversity to substance us
• Oxygen • Carbon dioxide • Food
• Medicine • Fuel • Water
Biodiversity exists on 3 different levels Genetic diversity The total number of genetic characteristics
in the genetic makeup of a species ( this can change due to selection pressures)
Species diversity Measure of diversity of different species in an eco-logical community
Ecosystem diversity Variations of different eco-system found in a region
Timeline about life on earth
Inquiry question; what is the relationship between evolution and biodiversity? - All organisms have developed from pre-existing organism - A common organ - Over billions of years, change in life on earth causes the biological diversity (
biodiversity)
Model 3 Biological Diversity 7. How microevolutionary changes can drive evolutionary changes and speciation
è Evolution at both micro and Macro levels establish evolution change, including
natural selection è Natural selection evolves over time
• the environment constantly challenges organisms • Selecting those characteristics that best adapt to the environment • Only the ‘ fittest’ will survive
Key terms Microevolution Evolution changes on a small scale within a single population, a
change in gene frequency over a short period of time Macroevolution Evolution on a large scale that takes place over millions of years
and results in new species Speciation The process which produces two or more species, often because
of geographical isolation
Speciation
è Diversification of species and branching into two or more species
• occurs as group adapt to different environments.
è Isolation occurs a species may form into distinct breeding populations.
• Selection pressures are often not the same when the population are in different environments.
• As a result, the environments select for different adaptations.
Evolution of the horse- Microevolution
è Horse is traced using • fossil records of lower leg bones • hooves • teeth
è horse evolution is believed to have been driven by
• Environmental selection pressures • Cool and drying climate
Model 3 Biological Diversity
è horses were once more abundant and diverse than they are today • Hyracotherium
§ flexible 4 towed feet • Medium sized ( mesohippus and merychippus)
§ grinding surfaced in their teeth § Eating grass § Became faster to flee predators
• Modern horse and piohippus § running on hard surfaces § elongated foot bones for longer stride
Evolution of the platypus- microevolution
è The platypus is a monotreme (an egg- laying mammal) è relationships between members of the platypus family
• ornithorhynchus platypus ( 100 000 years to
present) § toothless living platypus § (60cm long) smaller
• obdurodon tharalkooschild platypus ( largest
species of platypus found) § toothed platypus § feed on wide range of
animals
• Obdurodon may be a closer relative of the living platypus
§ toothed with fully rooted molars
• modern day platypus § duck billed § toothless § semi aquatic § webbed feet § tail like a beaver § covered in short waterproof fur
Model 3 Biological Diversity 8. Darwin and Wallace’s theory of evolution by natural selection
è Evolution of a species involes a CHANGE in CHARACTERISTICS ( GENETIC MAKEUP) OF
A POPULATION OVER TIME • Isolation ( GEOGRAPHICAL) • MUTATION and or SEXUAL REPRODUCTION ( PROVIDING a SOURCE OF
VARITATION IN A SPECIES) • NATURAL SELECTION
Divergent Evolution occurs when different species arise from a common ancestor
due to isolation from one another and adaptation to different enviroments
Natural selection can result in changes within a species If a population is ISOLATED in two different environments. If the changes in these isolated population becoming so different a new species may be formed ( SPECIATION)
Splitting A species could SPLIT FAIRY EQUALLY into TWO POPLUATIONS that evolve differently until they eventually become separate species
Budding
A small part of the SPECIES POPULATION COULD “bud off” from the MAIN PART and EVOLVE RAPIDLY ( in geological time ) to form a NEW SPECIES while leaving MOST OF THE ORGINAL SPECIES POPULATION UNCHANGED.
Convergent Divergent Parallel evolution
Model 3 Biological Diversity Convergent evolution Is a process that leads to SUPERFICIAL SIMILARITIES IN DIFFERENT
SPECIES that are NOT closly related. This is due to these ORGANISM LIVING in the SAME HABITAT or having the SAME LIFESTYLE so they are exposed to the SAME ENVIROMENTAL SELECITION PRESSURES. Natural selection can explain why they have similar characteristics even though they are distantly related.
è Convergent evolution has led to a dophin ( mammal), shark ( fish) and penguin ( bird) all having a streamlined shape due to the environmental SELECTION PRESSURES of the aquatic enviroment.
Shark Dolphin Similarities Streamlined
o body shape o colour
o fins and flippers Differences o Fish
o Cartilaginous skeleton o Ectothermic o Produce eggs
o Mammal o body skeleton o Endothermic o Produce live young
Model 3 Biological Diversity 9. The difference between punctuated equilibrium and the gradual process of natural
selection.
The rate of evolution has been much debated , with two model being proposed è Punctuated equilibrium – proposed by Stephen Jay Gould in 1970s è Gradualism – Dawins
Punctuated equilibrium A model of evolution that is backed by sufficient fossil
evidence which shows that some species remained essentially the same way for millions of years and then underwent short periods of very rapid major change.
è This means that most of a SPECIES existence is spent in STASIS and little time is spent
in ACTIVE EVOLUTIONARY CHANGE è The STIMULUS for rapid evolutionary change is when some crucial factor in the
environment changes • Volcanic activity • Glaciation
è The fact that there are VEARY FEW TRANSITIONAL FORMS in the fosil record supports the idea
Gradualism Dwain’s long- held view that evolutionary change occurred gradually over a long period of time
è There is evidence in the FOSSIL RECORD TO
SUPPORT GRADUALISM. • The evolution of the horse
Model 3 Biological Diversity
10. Evidence supporting Darwin and Wallace’s theory of evolution by natural selection?
The Theory of evolution
è The theory of evolution states that LIFE FORMS ON EARTH HAVE GENETICCALLY CHANGED WITH TIME.
• Different species have GRADUALLY developed in response to changing environments.
• These changes have usually occurred SLOWLY over millions of years. è Over time species have not remained constant- they have changed.
• New species have arisen • others have become extinct
è There has been a general change of SIMPLE TO MORE COMPLEXT forms of life
Biochemical evidence Involves the study of the structure and function of the many chemicals that are found in living organisms.
è The FEWER the differences in base sequence ( order) the more CLOSELY related the
organism is.
è In this technique the EXACT order of NUCLEOTIDE BASES in the gene ( DNA) of one species is COMPARED with the SEQUENCE in a similar DNA section of a second species.
Advantages of Biochemical evidence Limitations of Biochemical evidence o It allows comparison of organisms o The results are quantitative and the
degree of difference can be measured • Allowing judgment based on
scientific critter rather than observation
o DNA revels the most detailed information
o Techniques are • complex • expensive • rely on highly specialised
technology • can only be performed in labs
Inquiry question; what is the evidence that supports the theory of evolution by natural selection?
- Studies of fossils - Geology - Living organisms - Biochemistry - Comparative - Embryology - biogeography
Model 3 Biological Diversity Comparative anatomy Similar anatomy across different species provide evidence of a
common origin
è compare the anatomy of different organisms we find examples where • different species have similar basic structures
è it provides evidence of a COMMON ANCESTOR
è Similar anatomy actors different species is referred to as HOMOLOGOUS STRUCTURES • Frogs, whales, lions, humans and bats have
similar structure § All have humours bone § Radius bone § Ulna bone
• Proportionate length of these bones varies
depending on how they have been modified as adaptions to different environments
§ Swimming § Flying § Walking § grasping
Comparative embryology Provides evidence for evolution since the embryonic forms of divergent groups are extremely similar
è if we compare the embryos of many different species in the early stages of
development they are very similar è provides evidence of a common ancestor
è Example
• all vertebrate embryos have § gills slits § arches § notochords § spinal cords § primitive kidneys
• fish embryos and human embryos both have gill slights § in fish they develop into gills § In human they disappear before birth
è Depending on the species the skin then deveopls into • Fish scals • Bird feathers or hair • Clasws • Nails of mammals
This is an example of how the structure of embryo’s in the early stages of development appears to be similar
Model 3 Biological Diversity But
The structure carries out different functions as they develop into organs.
Biogeography Is the study of distribution of species in different geological regions on the earth
è Earth has a number of biogeographical
regions each with its own environmental features ( selection pressures)
• each regions contains species with specific adaptions that increase there survival
è distribution patterns provide evidence that species have originated from a COMMON ACESTOR and when ISOLATED, have evolved into NEW SPECIES
è evolution is in conjunction with the moment of tectonic plates over time
Fossils Any preserved remains of past organisms
è The development of techniques to date fossils provides scientist with a more accurate picture of
• How life on earth was formed • Which species evolved first and the evolutionary order of species • How species evolved to occupy diverse and changing ecosystems • Timescale of evolution • When certain major events occurred
Fossils
Relative dating techniques
Provides evidence of the sequence of geological events but not the exact dates of an event.
Absolute dating techniques
Eliminates that decay spontaneously at a defined rate; the rate of decay is used to date the formation of igneous rocks
Radioactive dating techniques
For fossils less then 6000 years old. Involves measuring the amount of C-14 isotopes to provide evidence of the data of organic material in fossils