Theme 6 : The continuity of life is based on heritable information in the form of DNA - PowerPoint PPT Presentation

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Theme 6 : The continuity of life is based on heritable information in the form of DNA. Chromosomes contain most of a cell’s genetic material in the form of DNA ( deoxyribonucleic acid ) DNA is the substance of genes

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Theme 6 : The continuity of life is based on heritable information in the form of DNA

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Theme 6 the continuity of life is based on heritable information in the form of dna l.jpg

Theme 6: The continuity of life is based on heritable information in the form of DNA

Chromosomes contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid)

DNA is the substance of genes

Genes are the units of inheritance that transmit information from parents to offspring


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Each chromosome has one long DNA molecule with hundreds or thousands of genes

DNA is inherited by offspring from their parents

DNA controls the development and maintenance of organisms


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Inherited DNA directs the development of an organism

Sperm cell

DNA

Nuclei

containing

DNA

Embryo’s cells with

copies of inherited DNA

Fertilized egg

with DNA from

both parents

Egg cell

Offspring with traits

inherited from

both parents


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Each DNA molecule is made up of two long chains arranged in a double helix

Each link of a chain is one of four kinds of chemical building blocks called nucleotides


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Nucleus

DNA

Nucleotide

Cell

(a) DNA double helix

(b) Single strand of DNA


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Genes control protein production indirectly

Why are proteins important?

Proteins are essential parts of organisms and participate in every process within cells

Many proteins are enzymes that catalyze (speed up) biochemical reactions and are vital to metabolism


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DNA controls protein production indirectly using RNA as an intermediary

DNA is transcribed into RNA then translated into a protein


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An organism’s genome is its entire set of genetic instructions

The human genome and those of many other organisms have been sequenced using DNA-sequencing machines

Knowledge of a cell’s genes and proteins can be integrated using a systems approach


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Advances in systems biology at the cellular and molecular level depend on

1) “High-throughput” technology, which yields enormous amounts of data

2) Bioinformatics, which is the use of computational tools to process a large volume of data

3) Interdisciplinary research teams


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Theme 7: Feedback mechanisms regulate biological systems

Feedback mechanisms allow biological processes to self-regulate

1) Negative feedback a change in a physiological variable triggers a response that counteracts the initial fluctuation

2) Positive feedback a change in a physiological variable triggers mechanisms that amplify the change


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Negative feedback:

Like a thermostat in the home: as the temperature rises (above the ideal normal temperature), the thermostat detects the change and triggers the air-conditioning to turn on and cool the house.

Once the temperature reaches its thermostat setting, the air conditioning turns off.


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Positive feedback:

The onset of contractions in childbirth: when a contraction occurs, the hormone oxytocin is released into the body, which stimulates further contractions.

This results in contractions increasing in amplitude and frequency.


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The Core Theme: Evolution accounts for the unity and diversity of life

“Nothing in biology makes sense except in the light of evolution”

Evolution unifies biology at different scales of size throughout the history of life on Earth


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Organizing the Diversity of Life

Approximately 1.8 million species have been identified and named to date, and thousands more are identified each year

Estimates of the total number of species that actually exist range from 10 million to over 100 million


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Grouping Species: The Basic Idea

Taxonomy is the branch of biology that names and classifies species into groups of increasing breadth

Domains, followed by kingdoms, are the broadest units of classification


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Species

Genus

Family

Order

Class

Phylum

Kingdom

Domain

Ursus americanus

(American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya


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The Three Domains of Life

The three-domain system is currently used, and replaces the old five-kingdom system

Domain Bacteria and domain Archaea comprise the prokaryotes

Domain Eukarya includes all eukaryotic organisms


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(a) DOMAIN BACTERIA

Prokaryotes

(b) DOMAIN ARCHAEA

(c) DOMAIN EUKARYA

Eukaryotes

Protists

Kingdom

Plantae

Kingdom Fungi

Kingdom Animalia


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  • DOMAIN BACTERIA – the most diverse and widespread of the prokaryotes

  • e.g., Staphylococcus spp., Lactobacillus spp., Streptomyces spp.

E. coli


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(b) DOMAIN ARCHAEA - prokaryotes that live in extreme environments, such as salt lakes and boiling hot springs (sometimes called extremophiles); believed to be the oldest organisms on Earth


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Domain Eukarya: includes three multicellular kingdoms:

1) Plantae

2) Fungi

3) Animalia

Other eukaryotic organisms were formerly grouped into a kingdom called Protista, though these are now often grouped into many separate kingdoms


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Protists

Kingdom Plantae

Kingdom Fungi

(c) DOMAIN EUKARYA

Kingdom Animalia


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Protists – are in multiple kingdoms; unicellular eukaryotes and their relatively simple multicellular relatives

e.g., Amoebas, Euglena (unicellular animal-like protists); Algae (multicellular plant-like protists)


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Kindom Fungi – absorb nutrients after decomposing organic matter (leaf litter, animal feces)


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Kingdom Plantae – consists of multicellular eukaryotes that carry out photosynthesis, the conversion of light energy to the chemical energy in food


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Kingdom Animalia – consists of multicellular eukaryotes that ingest other organisms

Basilisk


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Unity in the Diversity of Life

There is unity in the diversity of life; for example:

- DNA is the universal genetic language common to all organisms

- Unity is evident in many features of cell structure


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Cilia of

Paramecium

Cilia of trachea

cells

Cross section of a cilium, as viewed

with an electron microscope


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Charles Darwin and the Theory of Natural Selection

Fossils and other evidence document the evolution of life on Earth over billions of years


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Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859

Darwin made two main points:

  • Species showed evidence of “descent with modification” from common ancestors

  • Natural selection is the mechanism behind “descent with modification”

Darwin’s theory explained the duality of unity and diversity


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Darwin observed that:

  • Individuals in a population have traits that vary

  • Many of these traits are heritable (passed from parents to offspring)

  • More offspring are produced than survive

  • Competition is inevitable

  • Species generally suit their environment


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Darwin inferred that:

  • Individuals that are best suited to their environment are more likely to survive and reproduce

  • Over time, more individuals in a population will have the advantageous traits

    In other words, the natural environment “selects” for beneficial traits


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Example: a population of beetles lives in an area that commonly experiences forest fires; these beetles vary in coloration, from light grey to black

Reproduction

of survivors.

Increasing

frequency

of traits that enhance survival and reproductive success.

Population

with varied

inherited traits.

Elimination

of individuals

with certain

traits.

1

2

3

4

Birds eat the beetles that they can see best (black beetles are more camouflaged) – as a result, black beetles live to reproduce, others do not. Black beetles are “selected for” and predominate in the population.


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Natural selection is often evident in adaptations of organisms to their way of life and environment

Bat wings are an example of adaptation


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The Tree of Life

“Unity in diversity” arises from “descent with modification”

For example, the forelimb of the bat, human, horse and the whale flipper all share a common skeletal architecture

Fossils provide additional evidence of anatomical unity from descent with modification


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For example, the finch species of the Galápagos Islands

Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendents

Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species


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Green warbler finch Certhidea olivacea

Warbler finches

Insect-eaters

Gray warbler finch Certhidea fusca

COMMON

ANCESTOR

Sharp-beaked

ground finch Geospiza difficilis

Seed-eater

Vegetarian finch Platyspiza crassirostris

Bud-eater

Mangrove finch Cactospiza heliobates

Woodpecker finch Cactospiza pallida

Tree finches

Insect-eaters

Medium tree finch Camarhynchus pauper

Large tree finch Camarhynchus psittacula

Small tree finch Camarhynchus parvulus

Large cactus

ground finch

Geospiza conirostris

Cactus-flower-eaters

Cactus ground finch

Geospiza scandens

Seed-eaters

Ground finches

Small ground finch

Geospiza fuliginosa

Medium ground finch

Geospiza fortis

Large ground finch

Geospiza magnirostris


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Green warbler finch Certhidea olivacea

Warbler finches

Insect-eaters

Gray warbler finch Certhidea fusca

Sharp-beaked

ground finch Geospiza difficilis

Seed-eater

Vegetarian finch Platyspiza crassirostris

Bud-eater


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Mangrove finch Cactospiza heliobates

Woodpecker finch Cactospiza pallida

Tree finches

Insect-eaters

Medium tree finch Camarhynchus pauper

Large tree finch Camarhynchus psittacula

Small tree finch Camarhynchus parvulus


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Large cactus

ground finch

Geospiza conirostris

Cactus-flower-eaters

Cactus ground finch

Geospiza scandens

Seed-eaters

Ground finches

Small ground finch

Geospiza fuliginosa

Medium ground finch

Geospiza fortis

Large ground finch

Geospiza magnirostris


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Scientists use two main forms of inquiry in their study of nature

The word Science is derived from Latin and means “to know”

Inquiry is the search for information and explanation

There are two main types of scientific inquiry: discovery science and hypothesis-based science


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Discovery Science (or Descriptive Science) – mainly involves describing nature

Discovery science describes natural structures and processes

- based on observation and the analysis of data

European black caps


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Types of Data

Data are recorded observations or items of information

Data fall into two categories

1) Qualitative: descriptions rather than measurements

2) Quantitative: recorded measurements, which are sometimes organized into tables and graphs

FYI – the word “data” is plural, “datum” is singular!

e.g., The data were collected from 120 nests.


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Induction

Inductive reasoning draws conclusions through the logical process of induction

Repeat specific observations can lead to important generalizations

For example, “the sun always rises in the east”


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Hypothesis-based Science – involves explaining nature

Observations can lead us to ask questions and propose hypothetical explanations called hypotheses


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The Role of Hypotheses in Inquiry

A hypothesis is a tentative answer to a well-framed question

A scientific hypothesis leads to predictions that can be tested by observation or experimentation


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For example

Observation: Your flashlight doesn’t work

  • Question: Why doesn’t your flashlight work?

    • Hypothesis 1: The batteries are dead

    • Hypothesis 2: The bulb is burnt out

  • Both of these hypotheses are testable


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Observations

Question

Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb


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Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb

Prediction:

Replacing batteries

will fix problem

Prediction:

Replacing bulb

will fix problem

Test prediction

Test prediction

Test does not falsify hypothesis

Test falsifies hypothesis


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Deduction: The “If…Then” Logic of Hypothesis Based Science

Deductive reasoning uses general premises to make specific predictions

For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction)


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A Closer Look at Hypotheses in Scientific Inquiry

A hypothesis must be testableand falsifiable

Hypothesis-based science often makes use of two or more alternative hypotheses

Failure to falsify a hypothesis does not prove that hypothesis

For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly)


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The Scientific Method

The scientific method is an process of inquiry

Hypothesis-based science is based on the “textbook” scientific method but rarely follows all the ordered steps

Discovery science has made important contributions with very little dependence on the scientific method


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Designing Controlled Experiments

A controlled experiment compares an experimental group with a control group

Ideally, only the variable of interest differs between the control and experimental groups


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A controlled experiment means that control groups are used to cancel the effects of unwanted variables

A controlled experiment does not mean that all unwanted variables are kept constant


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Limitations of Science

In science, observations and experimental results must be repeatable

Science cannot support or falsify supernatural explanations, which are outside the bounds of science


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Theories in Science

In the context of science, a theory is:

- Broader in scope than a hypothesis

- General, and can lead to new testable hypotheses

- Supported by a large body of evidence in comparison to a hypothesis


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What a theory is NOT:

In ordinary speech, "theory" is often used to mean "guess" or "hunch,"

- in scientific terminology, a theory is a set of universal statements that explain some aspect of the natural world

A scientific theory is held with a high degree of confidence and is supported by enough physical evidence to make its abandonment unlikely


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Examples of a theories in Biology:

- The Cell Theory (1838) - all known living things are made up of cells

- Darwin’s Theory of Evolution (1859)

- Mendel’s Laws of Inheritance (1865) - transmission of hereditary characteristics from parent organisms to their children

Robert Hooke’s cork cells


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Theories are not easily discarded

New discoveries are first assumed to fit into the existing theoretical framework

It is only when, after repeated experimental tests, the new phenomenon cannot be accommodated that scientists seriously question the theory and attempt to modify it


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Scientific theories therefore represent the reality of the physical world

To say “It's only a theory” is naïve and exhibits a lack of understanding of science and the scientific method

Example:

It is unlikely that a person will step off a tall building on the assumption that they will not fall, because "Gravity is only a theory."


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  • Changes in scientific thought and theories occur

  • sometimes revolutionizes our view of the world

  • the key force for change is the scientific method and its emphasis on experiment


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Model Building in Science

Models are representations of natural phenomena and can take the form of:

  • Diagrams

  • Three-dimensional objects

  • Computer programs

  • Mathematical equations


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From

body

From

lungs

Right

atrium

Left

atrium

Right

ventricle

Left

ventricle

To lungs

To body


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The Culture of Science

Most scientists work in teams, which often include graduate and undergraduate students

Good communication is important in order to share results through seminars, publications, and websites

Results are subject to peer-review: other biologists review experiment; can only publish if passes peer-review


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Science, Technology, and Society

The goal of science is to understand natural phenomena

The goal of technology is to apply scientific knowledge for some specific purpose

Science and technology are interdependent

Biology is marked by “discoveries,” while technology is marked by “inventions”


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Example: the discovery of DNA by James Watson and Francis Crick allowed for advances in DNA technology such as testing for hereditary diseases

Ethical issues can arise from new technology, but have as much to do with politics, economics, and cultural values as with science and technology

The combination of science and technology has dramatic effects on society


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The end


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