how do we define life and
TRANSCRIPT
HOW DO WE DEFINE LIFE ANDWHAT DO WE KNOW ABOUT IT?
Please turn to page 86 in your notebook so we can finish these notes from the beginning of the unit.
What makes life different?
• Defining what it means to be a living thing has proved very difficult for biologists.
• The dynamism of life is due to four linked qualities, all instructed by deoxyribonucleic acid (DNA):• Metabolism:making or taking energy for survival.
• Living organisms need fuel to keep themselves going• Homeostasis: regulating internal functions to maintain health and
survive. • As the environment is always changing, living organisms adapt to new
information
BIG HISTORY PROJECT / UNIT 5 / LIFE
What makes life different?
• Reproduction: making copies of themselves. • Since all living organisms die, they need to reproduce to perpetuate
their species.• Adaptation: adjusting each generation to better survive in a changing
environment. • The theories of Charles Darwin and the nature of DNA are critical to our
understanding of life and how it works. • Members of each species compete for resources, mates, and survival:
those who survive pass on the traits that made them successful to their offspring.
Charles Darwin
• 19th century biologist• Published On the Origin of Species in 1859• His greatest achievement was to explain how life changes and
adapts.• He observed that slight changes were constantly occurring and
those that favored survival persisted.• Over time, this led to a more viable species.• He surmised that since environments were constantly changing,
biological change is an endless process.
Evidence for Evolutionary Change
• Darwin knew that fossils provided evidence of changes in living organisms over time, and today we can track such changes over 3.5 billion years.
• He also saw that there were subtle links between different species that showed that they were related.
Evidence for Evolutionary Change
• In the twentieth century more evidence emerged to support Darwin’s theories.
• Geologists realized that the Earth is old enough for such processes to have generated the huge variety we see around us
• Biologists have learned how reproduction works, and what causes the tiny errors that drive evolutionary change.
Evidence for Evolutionary Change
• We now know that the code for all living organisms is contained in huge molecules of DNA, billions of atoms in length, organized in a long double helix that contains and preserves the information needed to make new copies of each organism.
Now turn to page 96 in your notebook so we can finish these notes from the article on Friday.
Background on “The Race”Why was the understanding of the structure of DNA so important?
Biochemists believed that understanding its structure would reveal how the molecule coded the instructions for copying new organisms.
What were some important aspects of this scientific race?The concept of “diffraction” – the pattern of X-rays bounding off atoms“X-ray crystallography” – diffraction gave information about each atoms location in the molecule and therefore helps to understand the structure.
Background on “The Race”How important were the contributions of other scientists who didn’t win the race?
Linus Pauling – in the early 1950s he had already concluded that the general shape of DNA must be a helix, or spiral.Maurice Wilkins – shared Franklin’s X-ray diffraction image to Crick and Watson who used it to create their Nobel Prize-winning model
What did understanding the structure of DNA tell us about life?Once we understood the structure of DNA it was then possible to understand how DNA molecules copy one another. Occasional mistakes in copying enable evolution to occur and each organisms to be unique.
Crick, Watson, and FranklinYou are responsible for the bottom part of this assignment which was supposed to be completed in class last Friday.
It is very likely that details from this article will be on tomorrow’s formative assessment and next week’s unit test.
How do Earth and life interact?
You should have this notes handout on pages 94‐95 in your notebook.
Linking Astronomy, Geology, and Biology
There is a very close relationship between the history and evolution of the Solar System, the Earth, and life on Earth. The interconnected nature of our world is captured in the idea of the biosphere, which refers to the surface regions of the Earth that have been shaped by biological, geological, and astronomical forces.
Linking Astronomy, Geology, and Biology
Changes in the Earth’s orbit and the Sun’s emissions have shaped the Earth’s atmosphere, and so has the activity of living organisms. Additionally, living organisms have helped form important geological features including some rocks and layers of coal or oil.
AstronomyThe amount of sunlight that reaches different parts of the Earth’s surface is determined by the shape of the Earth’s orbit as well as its tilt; changes in these two factors are at least partly responsible for long‐term changes in the Earth’s climate, such as the appearance in the last few million years of regular ice ages.
AstronomyAsteroid impacts have also significantly affected the biosphere. Early in the Earth’s history such collisions were common, but they became rarer about 4 billion years ago.
AstronomyOne of the most spectacular impacts that has occurred since that time was when an asteroid landed about 65 million years ago near what is today Mexico’s Yucatán Peninsula. It caused vast tsunamis and raised huge clouds of dust that blocked out sunlight long enough to destroy most dinosaurs.
AstronomySudden changes like this often lead to the very rapid evolution of new species from those that survive; this process is known as an evolutionary radiation. For example, the disappearance of dinosaurs allowed mammals to flourish and diversify. Humans are a part of this mammalian radiation.
GeologyPlate tectonics has rearranged the Earth’s continents, created new oceans, and raised mountains. By changing ocean and wind currents, plate tectonics has transformed global climates. In addition, plate tectonics affects the diversity of living organisms.
GeologyWhen most continents are joined together, as they were about 200 million years ago, there are fewer species (less bio‐diversity) because species must compete within a single, huge arena. But when landmasses are separated as they are today, evolution can take its own course on each continent, island, and continental shelf, which leads to much greater diversity.
BiologyPhotosynthesis is one biological process which has shaped the biosphere: when organisms that were capable of photosynthesis began pumping oxygen into the atmosphere, it had a profound effect.
At first, this oxygen combined with elements such as iron and formed huge red bands of rust; after about 2 billion years, free oxygen began to appear in the atmosphere.
BiologyOxygen was poisonous to many species, so rising oxygen levels drove many living things to extinction.But some species (including most eukaryotes) evolved ways of using oxygen to extract energy. Eras with unusually high oxygen levels and low carbon dioxide levels seem to have been extremely cold.
BiologyThe formation of rocks from living organisms is another case where biological processes have shaped the biosphere.
Rocks such as limestone and chalk are formed from the fossils of dead organisms, particularly those with shells. Petroleum‐rich shale forms from ancient plant matter.
BiologyIn the last few hundred million years, the burial of once‐living organisms has created the huge reserves of coal, oil, and natural gas that we use today.
How and why have people misused Darwin’s ideas?