Biodiversity and Classification

Biodiversity and Classification

Biodiversity

• Biological diversity is usually the sign of a healthy ecosystem.

• The greater the diversity of organisms with in an ecosystem, the greater is the chance that some of those organisms will be able to survive change.

Biodiversity

• There are two levels of biological diversity:

1. Genetic diversity, which describes the variety of genes that code for different traits in a given species

2. Species diversity, which describes the number of different species.

Classification

• It is often difficult to determine if subtle physical differences are variation within a species or variation between different species of closely related organisms.

• Therefore, scientists need a classification system to help them study ecological diversity.

Taxonomic Systems

• Taxonomy – the science of classification according to the inferred relation ships among organisms

Taxonomic Systems

• Biological classification systems have two main purposes:

1. Identifying organisms 2. Providing a basis for recognizing natural

groupings of living things.

Taxonomic Systems• Carl Linnaeus (1707-1778)• Developed a system of

classification based on an organism’s physical and structural features, and operated on the idea that the more features organisms have in common, the closer their relationship.

Taxonomic Systems

• Carl Linnaeus (1707-1778)• He was the first to use:• Binomial nomenclature a method of

naming organisms by using two names – the genus name and the species name.

Taxonomic Systems

• Scientific name is often based on some characteristic such as colour or habitat:

• Example– Castor canadensis

• Caster meaning beaver and canadensis meaning from Canada

• The first part of any scientific name is called the genus. The second part is called the species.

Taxonomic Systems

• The two-name system provides an added advantage by indicating similarities in anatomy, embryology, and evolutionary ancestry.

Taxonomic Systems

• Present classification system there are seven main levels or taxa.

1. Kingdom2. Phylum3. Class 4. Order5. Family6. Genus 7. species

• Today most scientists believe that organisms have changed over time. The history of the evolution of organism is called phylogeny.

• Relationships are often shown in a type of diagram called a phylogenetic tree.

Assignment

• Read pages 134-139 • Do questions 1-7 on page 139• Investigation pg 162

Evidence of a Changing Earth

• Evidence of evolution comes from many lines of investigation.

• Some from direct observation and some more indirect.

• Evidence gathered from:– Direct Evidence:

– Fossils– Radiometric dating

– Indirect Evidence• Comparative Anatomy• Homologous structures• Analogous structures• Embryology• Vestigial Organs• Physiology• Behaviour• Plant and animal breeding• Biochemistry and genetics• The geographic distribution of species

Evidence from Fossils

• Paleontology – The study of fossils• Fossilized remains, impressions, and

traces of organisms from past geological ages provide scientists with direct physical evidence of past life.

Evidence from Fossils

• Patterns found in fossils:1. Different species lived on Earth at various

time in the past.2. The complexity of living organisms generally

increases from the most distant past to the present.

3. Living species and their most closely matching fossils are typically located in the same geographic region.

Fossilization occurs in many ways· Organic components of the

organism are replaced by minerals. · Impressions left by organisms are

preserved by the solidification of mud.

· Organisms can sometimes be caught in amber and preserved

– Mammoths, bison and other extinct mammals have been found frozen in Arctic ice.

– Acidic Bogs-conditions retard decomposition

Do you have a date??· Radiometric dating

· use the radioactive decay of certain elements to determine the age fossils

– Example: Carbon-14

Evidence From Biogeography

• Biogeography explores the variation and distribution of live over the Earth’s surface, both today and the past.

• Earth’s landmasses have undergone dramatic changes by the process of continental drift.

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Evidence From Biogeography

• Evidence from biogeography suggest that different species evolved independently in isolated parts of the world.

Evidence of Evolution from Biology

• A comparison of the physical anatomy and genetic makeup of organisms also provides evidence.

Evidence from Anatomy

• Comparative Anatomy– Homologous structures

· Structures having similar genetic origin but different uses in different species.

• Adaptive radiation: The pentadactyl limb has evolved to suit many niches: digging, running, flying, swimming, etc.

Ex: Flipper of dolphin and a forelimb of dog suggests a common ancestor

Indirect Evidence For Evolution• Analogous structures

· Structures which are similar in function and appearance but came from different ancestors.

· Examples: wing of an insect and a bird

– Good indicators that these organisms did not evolve from a common ancestor

– Illustrates convergent evolution • development of similar forms from

unrelated species due to adaptation to similar environment

More Indirect Evidence for Evolution

– Embryology· The study of organisms in their early stages

of development.· Closely related organisms go through similar

stages in their embryonic development· similarities in embryos suggests these

organisms have an evolutionary relationship.

Embryology

Embryology

–Vestigial Organs• Structure with no known function in present• Examples: coccyx and appendix in

humans, vestigial leg bones in snakes

Evidence from Biochemistry

• Evidence of evolution has also been found by comparing biochemical characteristics of different species.

• Biochemical Evidence – Analysis of chemicals can be used to show

evolution– DNA and cytochrome enzyme C (respiration)

are similar in all organisms– DNA analysis-used determine how closely

related organisms are· suggest a common ancestor

Assignment

• Read pages 140-148• Do questions 1 & 2 on page 143 and

question 3 on pg 149

Lamarck and Darwin

Source of Variation:

· Inherited: Determined by the DNA (genetic material) inherited from the parent

· i.e. hair, eye and skin color

· Acquired: Developed over life time. · i.e. basketball skills, musical ability

History of Evolution

Lamarck’ Theory

• Lamarck believed that new species were continually being created by spontaneous generation– Spontaneous generation – the belief that

living things arose from non-living matter.

Lamarck’ Theory• Theory of Use and Disuse: Use-remains strong.

Disuse-weakens and disappears. For example snakes legs.– USE Each body part possesses a “will”

which allows it to change in order to better fit its environment. • Eg. Short necked giraffe stretches its neck to reach

tree tops and it develops a longer neck– DISUSE If a body part is not used it will

begin to disappear • Eg. Nocturnal animals (ie. Bats) lose their vision

Lemarck’ Theory

• Theory of Acquired Traits: Traits acquired in life time could be passed on to offspring. Inheritance of acquired characteristics

Problems with Lamark’s theory

• “Use and Disuse” implies an organism can sense its needs and physically change to meet those needs.

• Acquired characteristics are not inherited• Never confirmed by experimentation.

Darwin’s Theory of Evolution

1. Overproduction

2. Variation.

3. Competition

4. Survival of the fittest

5. Passing on of successful traits (speciation)

Overproduction• Overproduction means that the number of

offspring produced by a species is greater than the number that can survive.

Variation

• Differences among traits occur among members of the same species.

• No two individuals are exactly alike• Caused by:

– Mutation– Sexual Reproduction

Struggle for existence• Competition • Organisms of the same species, as well as

those of different species, must compete for limited resources such as food, water, and a place

• Natural selection: Nature selects the organisms that survive

Survival of the Fittest-Natural Selection

• The most fit individuals survive• Fittest means that the individuals are best

suited to the environment

Origin of new species (speciation)

• Successful individuals reproduce and pass on their traits

• Over numerous generations, new species arise by the accumulation of inherited variation

• When a type is produced that is significantly different from the original, it becomes a new species.

Comparison of Lamarck and Darwin

Darwin• Organism vary

regardless of the environment

• The environment then determines whether a variation is harmful (die) or helpful (survive)

Lamarck• Individuals change

to suit their environment

• Change is based on the need or “want” to change

Sources of Inherited Variation

• Variability in a species may arise from two biological processes:

1. Mutations 2. Sexual reproduction

Mutations

• DNA, the hereditary material, is found in the chromosomes of a cell.

• Genes are segments of DNA that code for Specific traits.

• Mutation - a random change in the DNA sequence in a chromosome.

Mutations

• Mutations can by caused by:1. Environmental factors

– Chemicals– Radiation

2. Errors that arise when cells replicate

Mutations

• Mutations are rare in individuals.

• Neutral mutation – a mutation that has no effect on the organism

• Harmful mutation – a mutation that reduces an organism’s fitness

• Beneficial mutation – a mutation that enhances an organisms’ fitness.

Mutations

• Summary:– Mutations occur at random, with harmful

mutations being more common than beneficial mutations.

– Harmful mutations are selected against and therefore do not accumulate over generations.

– Although beneficial mutations are rare, they are selected for and may accumulate over the generations.

Sexual reproduction and Variability

• Asexual reproduction – production of offspring from a single parent: offspring inherit the genes of that parent only. – All offspring are identical to parents.

Sexual reproduction and Variability

• Sexual reproduction – the production of offspring by union of sex cells from two different parents.– Offspring are never identical to the parents or

to other siblings.

• Why are sexually-reproducing species so variable? There are three reasons.

1. Sexually-reproducing species have two copies of each gene. One from each parent.

2. The assortment of genes that an offspring inherits from either parent is determined randomly.

3. Sexually reproducing species choose different mates.

Speciation and Evolution

· Species· A group of similar organisms which share

a common gene pool· Organisms of the same species normally

interbreed in nature and are capable of producing fertile offspring

• Population:

– A group of individuals of the same species occupying a given area at a certain time

Speciation

• Speciation – the formation of new species.

• Most new species are believed to arise by a three-step process called allopatric speciation.

1. A physical barrier separates a single interbreeding population into two or more groups that are isolated from each other.

Speciation

2. Natural selection works on the separated groups independently, resulting in inherited differences in the two populations. (defenses in selective pressures).

3. Physical and behavioral differences accumulate can no longer be sexually compatible.

• New species evolve from a common ancestor in response to a new environment

• Eg. From a common finch with a mid-sized beak the following finches evolved

• Finch with a long beak for poking wood• Finch with a short, hard beak for cracking seeds• Finch with a long beak for drinking nectar

Rate of Evolution• Theory of gradualism – the idea that speciation

takes place slowly.• Theory of punctuated equilibrium- the idea that

species evolve rapidly followed by a period of little or no change. This theory has three main assertions:

1. Many species evolve very rapidly in evolutionary time

2. Speciation usually occurs in small isolated populations

3. After an initial burst of evolution, species are well adapted to their environment and do not need to change significantly for a long period.

Methods of speciation:

• Transformation of one species into another

• Branching evolution: one or more species branch off a parent species which continues to exist.

Divergent evolution – evolution into many different species.

Adaptation and Change• Convergent Evolution

– the development of similar forms from unrelated species due to adaptation to similar environments.

– Ex: the torpedo shape of dolphins and sharks. Over time, the two began to look more and more alike.