Life: Chemical, Cellular, and Evolutionary Foundations. Chapter 1

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1 Life: Chemical, Cellular, and Evolutionary Foundations Chapter 1

2 Core Concepts 1. The scientific method is a deliberate way of asking and answering questions about the natural world. 2. Life works according to fundamental principles of chemistry and physics. 3. The fundamental unit of life is the cell. 4. Evolution explains the features that organisms share and those that set them apart. 5. Organisms interact with one another and with their physical environment, shaping ecological systems that sustain life. 6. In the 21 st century, humans have become major agents in ecology and evolution.

3 What is Biology? Biology: The science of how life works It is understood at many levels: -Molecular mechanisms within the cell -Integrated actions of many cells within an organ or body -Interactions among different organisms in nature Biologists: Scientists who study life, understand the processes from molecular level in a cell to integrated actions of cells in organs or body to interactions among different organisms in nature

4 A Humming Bird Visiting A Flower What motivates this behavior? -Is the bird feeding? -Does the bird choose this flower because of its color? -Does the flower benefit from the bird s behavior?

5 1.1 THE SCIENTIFIC METHOD A good hypothesis makes predictions about observations or experiments not yet made or run. These predictions can be tested. A hypothesis supported by a large body of experiments and observations, is a theory. In general conversation, the term theory is often synonymous with hypothesis. But in science, a theory is fact.

rock layers corresponding to the time of dinosaur extinction.

6 Let s put the Scientific Method into practice. Observation: Iridium, a common component of meteorites, was found in rock layers corresponding to the time of dinosaur extinction. Hypothesis: A large meteorite disrupted communities on land and in the sea, causing the extinction of dinosaurs.

7 Prediction: Independent evidence of a meteor should be found in rock layers corresponding to the time of the extinction, and should be rare or absent in older and younger layers. Further Observations: Conclusion: A giant meteor struck the Earth 65 million years ago, causing the extinction of dinosaurs.

8 1.2 CHEMICAL AND PHYSICAL PRINCIPLES CHARACTERISTICS OF LIVING ORGANISMS 1. Complex ( Structure and Function) 2. Ability to change in response to environment 3. Ability to reproduce 4. Capacity to evolve Living organisms are made up of CELLS, Cells are made up of chemical compounds. Living organisms need ENERGY to live.

9 COMPOSITION OF EARTH AND HUMAN BODY Living and nonliving worlds share the same chemical foundations and obey the same physical laws. There is nothing special about our chemical components when taken individually. The relative abundances of elements differ greatly. Earth s Crust oxygen, silicon, aluminum, iron, calcium. Organisms oxygen, carbon, hydrogen

10 1 st LAW OF THERMODYNAMICS Energy can neither be created nor destroyed, it can only be transformed from one form into another. All organisms obtain energy from the sun or from chemical compounds. From this energy, some is used to do work (moving, reproducing, and building cellular components) while the rest is dissipated as heat.

11 2 nd LAW OF THERMODYNAMICS The degree of disorder in the universe tends to increase. The amount of disorder in a system is the entropy of the system.

12 FRANCESCO REDI EXPERIMENTATION Living organisms come from other living organisms. Francesco Redi tested this hypothesis in the 1600s by proving that maggots come from flies laying their eggs.

13 FRANCESCO REDI EXPERIMENTATION In this experiment: Three jars with meat differed only in their covering (open jar, gauze-covered jar, and sealed jar). Redi observed that only the jar that was left open became covered in maggots because flies were allowed to lay their eggs on the meat These results support the hypothesis that living organisms come from other living organisms Life does not spontaneously arise from nonliving materials is the conclusion of this experiment.

14 LOUIS PASTEUR EXPERIMENTATION Pasteur tested the hypothesis that microorganisms can arise by spontaneous generation.

15 LOUIS PASTEUR EXPERIMENTATION In this experiment: Sterilized broth was filled in a straight-neck flask and in a swan-neck flask. Observations: The straight-neck flask allowed dust particles carrying microbes to fall into the sterile broth The swan-neck flask prevented dust from getting inside These results do not support the hypothesis that living organisms come from other living organisms Pasteur rejected the hypothesis that microbes arise spontaneously. Instead, exposure to microbes carried on airborne dust particles is necessary for microbial growth.

16 1.3 THE CELL The simplest self-replicating entity that can exist as an independent unit of life B A C T E R I A A L G A E Y E A S T

17 LIVING ORGANISMS Unicellular- a single cell (Bacteria, Yeast etc.) or Multicellular - an ensemble of many cells. (Cheetahs, Humans etc.)

CELL DIVERSITY: Most cells are tiny, not detected by the naked eye, yet there are some specialized cells that are quite large. a) Skin cells: 100 micron, or 0.

18 CELL DIVERSITY: Most cells are tiny, not detected by the naked eye, yet there are some specialized cells that are quite large. a) Skin cells: 100 micron, or 0.1 mm, in diameter b) Some nerve cells in the human body have axons that extend a meter in length c) Ostrich egg cell Each of these cell types contains a stable blueprint of information in a molecular form.

19 ESSENTIAL FEATURES OF A CELL 1. It has aa ability to store and transmit information (blueprint of information in molecular form, DNA) 2. It has a boundary that separates the interior of the cell from its external nonliving environment ( Plasma membrane) 3. It has the ability to harness energy from the environment. (Metabolism)

20 1. DNA STORES AND TRANSMITS INFORMATION Cells contain a stable blueprint of information in a molecular form, that is DNA. DNA is a double-stranded helix with each strand made up of a varying sequence of four different kinds of molecules connected end to end. It is the sequence of these molecules that encodes a cell s information. This information can also be replicated & passed from cell to cell/from one organism to its progeny.

21 1. DNA- STORES AND TRANSMITS INFORMATION THE CENTRAL DOGMA This is the basic flow of information in a cell. DNA is transcribed into RNA, RNA is translated into protein. A gene is the DNA sequence that corresponds to a specific protein product.

2. PLASMA MEMBRANE Membranes define cells and spaces within cells The plasma membrane separates the living material within the cell from the nonliving

22 2. PLASMA MEMBRANE Membranes define cells and spaces within cells The plasma membrane separates the living material within the cell from the nonliving environment around it. It controls the exchange of material between the cell and the environment. Some cells have internal membranes that divide the cell into compartments.

23 2. PLASMA MEMBRANE. Membranes within the cells differentiate the cells Not all cells have a nucleus, and are thus classified as CELLS Prokaryotes Do not have a nucleus Domain Bacteria and Archaea Eukaryotes Have a nucleus Domain Eukarya

24 3. Harnessing Energy: METABOLISM Energy from environment is converted into a form that can be used by cells. Energy comes from two sources: a) the sun b) chemical compounds Regardless of the source of energy, in all organisms chemical reactions break down macromolecules, releasing energy, and storing it in a chemical form, ATP Cells use ATP to carry out life processes.

25 3. METABOLISM The term metabolism describes chemical reactions that cells use to convert energy from one form to another by : i) Building molecules (anabolism) and ii) Break down of molecules (catabolism).

26 Aren t viruses smaller than cells? Are they the smallest living organisms? A virus is genetic material in need of a cell. 1. A virus can store and transmit information. (DNA or RNA) 2. A virus has a plasma membrane (protein coat). 3. A virus can harness energy from the environment. Cells can break down chemical compounds, releasing energy and converting it into a usable form (ATP). Viruses cannot; they require cells as hosts in order to read and use the information contained in their genetic material. They require cells as hosts in order to replicate.

27 VIRUS: Genetic Material in need of a cell Virus is - i) An agent that infects cells. ii) Smaller and simpler than a cell. iii) Has genetic material as DNA or RNA. iv) Has a protein coat as an envelope. It is not a cell as it cannot harness energy from the environment.

28 1.4 EVOLUTION Evolution is Change over time. Explains both: The features that ORGANISMS SHARE and Those that SET THEM APART.

29 Most of life s diversity, and so most of its deep evolutionary history, is microbial. ARCHAEA Change over time. BACTERIA Proposed position of root Time runs from the root to the branches. Change over time. EUKARYOTES Plants Animals All land plants lie on this branch. Animal diversity lies on this branch of the tree.

30 1.4 EVOLUTION The variation within a population of organisms can be inherited.(natural Selection) The variants best able to grow and reproduce in a particular environment will contribute disproportionately to the next generation. This leads to a change in the population over time, or Evolution

31 VARIATION CAN BE GENETIC OR ENVIRONMENTAL Variation Environmental For example, apples on a tree are exposed to different environmental factors (sunlight, shade, insects). Genetic Differences in individual DNA RNA Proteins causes differences in physical appearance, for example apples like Green Granny Smith, Yellow Golden Delicious, Scarlet Red Delicious

32 1.4 EVOLUTION The ultimate source of genetic variation is mutation. Organisms show a nested pattern of similarity, Humans more similar to primates, Primates more similar to mammals, Mammals more similar to vertebrates, and so on. Evolution can be demonstrated by laboratory experiments.

33 PHYLOGENETIC TREE IN PRIMATES

34 RELATEDNESS AMONG SPECIES Evolutionary theory predicts that new species arise by the divergence of populations through time from a common ancestor. As a result, closely related species are likely to resemble each other more closely than they do more distantly related species. Here, we can see a phylogenetic tree showing the evolutionary relationships among primates. The branches represent different groups of organisms, and at each node, you can see the most recent ancestor.

35 Tree of Life Most of life s diversity, and so most of its deep evolutionary history, is microbial. ARCHAEA BACTERIA EUKARYOTES Plants All land plants lie on this branch. Proposed position of root Time runs from the root to the branches. Animals Animal diversity lies on this branch of the tree.

36 Tree of Life 1.Today, three domains of life are recognized. 2. Both the bacteria and archaea lack a nucleus and are therefore prokaryotes, while the eukaryotes have a nucleus. 3. However, in spite of the similar cellular structure of the bacteria and the archaea, the eukarya and archaea are closely related. 4. Biologists call this full set of evolutionary relationships among organisms the Tree of Life.

37 Elena and Lenski demonstrate evolution through experimentation

38 Elena and Lenski demonstrate evolution through experimentation Elena and Lenski grew E. coli in liquid medium containing a poor food source, succinate. They hypothesized that, if a mutation occurred that increased the bacteria s ability to utilize the succinate, then those particular mutated bacteria would be able to reproduce at a faster rate than those that did not have the mutation. In the beginning of the experiment, the researchers froze some of the ancestral (starting bacterial) population Over 20,000 generations, they grew what was believed to be the evolving population on succinate. As the experiment progressed, they took samples of the evolving bacterial population at periodic intervals and grew them together with samples of the ancestral population. They compared the rate of growth of the two different populations. The bacteria over time did evolve an improved ability to use succinate as their food source.

39 1.5 ECOLOGICAL SYSTEMS Ecology: the study of how organisms interact with one another and with their environment

40 1.5 ECOLOGICAL SYSTEMS Anatomy, physiology, and behavior shape ecological systems. 1.The bee visits a flower for food. The bee chooses the flower based on its color, odor and the expectation of a meal. In turn, the bee pollinates the flower when it visits a neighboring flower for food. 2.The trees in a rain forest all require water and nutrients and compete for the supplies of these materials. 3.Plants provide the food for many animals. The leaf-cutter ants cut slices of leaves to take to their nests, the leaves will grow fungi that the ants eat. These interactions play an important role in evolution.

41 SO WHAT IS OUR ROLE IN EVOLUTION? Some species have benefited from human activity Our crowded and not always clean environments have increased the populations of roaches and rats. Agriculture has increased the abundance of grapes, corn, cows, and apple trees.

42 SO WHAT IS OUR ROLE IN EVOLUTION? Some species have not benefited from human activity Hunting, fishing, changes in land use, and other human activities have caused a decline or extinction of some species Some extinct species are: -Dodo, Passenger pigeon, Bali tiger, Dusky seaside sparrow In addition, white rhinos have diminished now.

43 WHY STUDY BIOLOGY? To understand the practical issues of life science Then, use these principles to - improve our lives - support lives of other living organisms - save the universe Solving biological problems requires an integrated understanding of life, Can be achieved by knowing molecular biology, cell biology, ecology. ALONG with chemistry, physics, engineering.

Biology 211 (2) Week 1 KEY!

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