CLOZE-What is Life?

An Evolutionary
Framework for Biology
An Evolutionary Framework for Biology
• What is Life?
• Biological Evolution: Changes over ________ of Years
• Major Events in the History of Life on Earth
• Levels of Organization of Life
• The Evolutionary Tree of Life
• Biology is a Science
What is Life?
• Life can be defined as an organized ________ unit capable of ________ , ________ and ___________.
What is Life?
• An organism's metabolism is its total chemical activity and consists of thousands of individual chemical________
• These reactions must be ________ for an organism to function.
• ________ provide this control and coordination.
What is Life?
• The internal environment of an organism must remain within a given range of physical and chemical conditions for that organism to remain healthy.
• ________ is the maintenance of a relatively stable internal condition, such as temperature.
What is Life?
• Reproduction with ________ is a major characteristic of life.
• The combination of reproduction and errors in the ________ of the genetic material results in biological evolution.
• Variations in the physical environment have helped drive the diversification of life.
• The differences among living things that enable them to live in different kinds of environments and adopt different lifestyles are called ________
Biological Evolution:
Changes over Billions of Years
• Count George-Louis Leclerc de Buffon (1707–1788) wrote Natural History of Animals and suggested the possibility of________
• Buffon observed the similarity of different mammals' limbs and suggested that the limbs of mammals were inherited from a common ancestor.

Biological Evolution:
Changes over Billions of Years
• Jean Baptist de Lamarck, a student of Buffon, suggested a mechanism:
§ That with continued ________ some structures become larger from generation to generation, whereas others become smaller from________
• Though Lamarck made important contributions, this theory of acquired structures is not accepted by scientists today.
Biological Evolution: Changes over Billions of Years
• In 1858, both Charles Darwin and Alfred Russel Wallace independently developed and proposed the theory of evolution by ________ selection:
• The reproductive rates of all organisms are sufficiently ________ that populations would be enormous if ________ rates did not balance reproductive rates.
• Differences or variations among individuals influence how well those individuals ________ and reproduce in changing environments.
• Traits that increase the ________ that their bearers will survive and reproduce are passed on to the next generation.
• Darwin called the differential survival and reproductive success of individuals ________ selection.

Major Events in the History of Life on Earth
• Life arose from nonlife.
• Chemical evolution led to the appearance of life about 4 ________ years ago.
• Random inorganic chemical interactions eventually produced molecules that had the property of acting as ________ to form similar molecules.
Major Events in the History of Life on Earth
• Around 3.8 billion years ago certain molecules became enclosed in compartments, or cells.
• Cells capture energy and replicate themselves, two fundamental characteristics of life.
• For 2 billion years, all organisms were unicellular ________ confined to the oceans.
Major Events in the History of Life on Earth
• About 2.5 billion years ago some prokaryotes acquired the ability to________
• The energy of sunlight was captured, and oxygen was generated as a waste product.
• Oxygen increased in concentration in the atmosphere, making ________ metabolism possible.
Major Events in the History of Life on Earth
• Another effect of oxygen was O3 (ozone) accumulation in the upper atmosphere.
• Ozone has the property of preventing excess ________ light from the sun from reaching Earth.
• Around 800 million years ago, ozone accumulation shielded the landmass from radiation enough to allow the movement of organisms to ____.
Major Events in the History of Life on Earth
• Some prokaryotic cells became large enough to attach, engulf, and digest smaller cells.
• About 1.5 billion years ago, some cells had surviving smaller cells within them: These were early ________ cells.

Major Events in the History of Life on Earth
• Two developments made the evolution of ________ organisms possible:
§ The ability of a cell to change its structure and function to meet the challenges of a changing environment
§ The ability of cells to stick together after they have divided and to act in a coordinated manner
• Once organisms became multicellular, it became possible for certain cells to specialize.
Major Events in the History of Life on Earth
• Sexual recombination, the combining of genes from two cells, appeared early in the evolution of life.
• Sex increased the rate of evolution:
§ Organisms that exchange genetic information produce offspring that are ________ variable.
§ Because environments are constantly changing, organisms that produce variable offspring have an advantage over those that produce genetically ________ clones.
Levels of Organization of Life
• Biology can be visualized as a hierarchy of units that include molecules, cells, tissues, organs, organisms, populations, communities, and the biosphere.
• To understand organisms, biologists must study them at all levels of organization, from low to high.


The Evolutionary Tree of Life
• All organisms on Earth today descended from an original ________ organism that lived around 4 billion years ago.
• Major evolutionary events have led to more complex organisms with larger quantities of information and more complex mechanisms for using it.
• Genetically independent groups, called species, have evolved.
The Evolutionary Tree of Life
• The terms simple and complex refer to an organism's level of complexity.
• The terms ancestral and derived distinguish characteristics that appeared earlier in evolution from those that appeared later.
• All organisms alive today have survived because of appropriate adaptations to their environments.


The Evolutionary Tree of Life
• Biologists have assembled a provisional Tree of Life using data from a variety of sources, including the fossil record and modern techniques of DNA sequencing.
• Three major life domains form the hierarchical scheme: Archaea and Bacteria (prokaryotes), and Eukarya (eukaryotes).

The Evolutionary Tree of Life
• Each species is identified by two names:
§ The first, the genus name, refers to a group of species that share a recent common ancestor.
§ The second name, the species name, identifies a single species with the genus.
• For example, the scientific name of modern humans is Homo sapiens.
Biology is a Science
• There are five parts to the hypothesis-prediction (H–P) system:
§ Making observations
§ Asking questions
§ Forming hypotheses, or tentative ________ to the questions
§ Making predictions based on these hypotheses
§ Testing the predictions by making additional observations or conducting experiments
Biology is a Science
• If the results of continued testing support the hypothesis, it may come to be considered a theory.
• If the results do not support the hypothesis, it may be modified or abandoned.
Biology is a Science
• Most tests of hypotheses are of two types:
§ Controlled experiments
§ The comparative method
Biology is a Science
• The H–P method was used to investigate why amphibian populations are declining dramatically in many places.
• Step 1: Making observations:
§ Scientists observed that amphibian populations are declining seriously in some parts of the world, but not in others.
§ Observations also showed that the declines were greater in the mountains than in adjacent lowlands.
Biology is a Science
• Step 2: Asking questions:
§ Why are amphibian declines greater at high elevations?
§ Why are amphibians declining in some regions but not others?
Biology is a Science
• Steps 3 and 4: Formulating hypotheses and making predictions:
• To develop hypotheses, scientists identified environmental factors that change with elevation, such as summer levels of UV-B radiation.
• Hypothesis: Declines in the populations of some amphibian species are due to global increases in UV-B radiation.
• Prediction: Experimentally reducing UV-B over ponds where amphibian are developing should improve their survival.
Biology is a Science
• Step 5: Testing hypotheses:
• The responses of tadpoles of two species of frogs that live in Australian mountains were compared.
• One species, Littoria verreauxii, had disappeared from high elevations; the other, Crinia signifera, had not.
• Scientists predicted that L. verreauxii tadpoles would survive less well than C. signifera if exposed to UV-B radiation typical of high elevations. Experiments confirmed this observation.
• Individuals of both species survived well when raised in tanks with filters that blocked UV transmission.


Biology is a Science
• Another hypothesis to account for regional differences in amphibian population declines:
§ Adverse effects of habitat alteration by humans and agricultural pesticides
• Prediction:
§ Amphibian declines should be greater in areas exposed to pesticides than in areas not exposed.
• This has been tested using the comparative method.

Biology is a Science
• It is important to distinguish science from nonscience.
• Science begins with observations and the formulation of hypotheses that can be tested and that will be rejected if significant contrary evidence is found.
Biology is a Science
• The study of biology has major implications for human life.
• The development of genetics provides a means to control human disease and agricultural productivity, capabilities that also raise important ethical and policy issues.
• The study of biology also helps us to understand the human impact on the biosphere.
• Currently, biological science is positioned at the forefront of many ethical, ________ social, and ________ challenges and dilemmas.