CHAPTER 1 a View of Life

CHAPTER 1 A view of life.

Defining Life Characteristics of life • Life defies a simple, one-sentence definition, and so life is recognized by what living things have in common, or their life characteristics. Cellular Order

Response to the environment Evolutionary adaptation

Regulation (Homeostasis) Reproduction Energy processing Growth and (Metabolism) development Cellular Order Eukaryotic & Prokaryotic cells. Evolutionary adaptation Response to the environment Reproduction • Reproduction requires the accurate transmission of the blueprint for an organism’s body (chromosomes made of DNA) from parents to offspring. • Organisms can have one set of chromosomes or more than one set. Organisms with one set are said to be haploid (example: bacteria, fungi). Organisms with two sets are said to be diploid (example: humans). • Reproduction can be asexual (if it involves one single organism) or sexual (if it involves two organisms). Growth and development Energy processing (Metabolism) • All living organisms require a constant input of free energy (energy available to grow and do work). • Free energy is used to create ordered body structures. Living organisms do not violate the second law of thermodynamics (entropy increases with time) because creating order releases large amounts of energy into the environment. • To obtain this energy, organisms can be photosynthetic (free energy obtained from the sun, like plants or algae) or chemosynthetic (free energy obtained from inorganic chemicals, like humans).

Regulation ( Homeostasis) • Homeostasis refers to a body’s ability to maintain a stable internal environment adequate for survival of the organism in the face of changing environmental conditions. • In animals, sensory receptors in the body constantly monitor internal conditions and relay the information to a nervous system. Responses generated by the nervous system are carried out by motor effectors. • The nervous system maintains homeostasis through the use of positive and negative feedback. Information Information RECEPTOR affects affects RECEPTOR Body’s Body’s temperature CONTROL temperature STIMULUS sensors CENTER sensors STIMULUS Body temperature Body temperature rises above 37.2oC falls below 37.2oC (99oF) (99oF)

Control Control mechanism mechanism RESPONSE when body when body RESPONSE temperature temperature Decreased blood flow rises falls Increased blood flow to skin to skin Decreased sweating Increased sweating Shivering Stimulus removed Stimulus removed Homeostasis restored Homeostasis restored

Thermoregulatory EFFECTOR center in brain EFFECTOR Negative Sends Sends feedback Blood vessels Blood vessels Negative and sweat commands commands and sweat glands feedback glands in skin to to in skin Skeletal muscles

Thermoregulation: an example of negative feedback. • Response stops the stimulus restoring homeostasis.

• Ethylene gas promotes fruit ripening. As ripened cells in the fruit produce ethylene more cells ripen, releasing more ethylene, which causes more cells to ripen... Transmission of genetic information

Interaction with other living organisms Organizing Life Levels of organization Atoms

Molecules 1 µm

Organelles 10 µm

Cell

Cells Tissues 50 µm Organs and organ systems Organisms Populations Communities Ecosystems

Different desert ecosystems… ! DESERT BIOME The BIOSPHERE Emergent Properties • Emergent properties result from the arrangement and interaction of individual component parts within a system. • Emergent properties characterize both biological and nonbiological beings. – For example, a functioning bicycle emerges only when all of the necessary parts connect in the correct way. When bones, muscles & feathers team up to form wings, the property of FLIGHT emerges. Nucleus DNA

Nucleotide

Cell

DNA’s properties are the result of all its parts working together.

(a) DNA double helix (b) Single strand of DNA Classifying Life Putting everyone in their right place

• Taxonomy is the branch of biology that classifies living organisms. Hierarchical Classification. • The taxonomic groups from broad to narrow are domain, kingdom, phylum, class, order, family, genus, and species.

Sus scrofa domesticus, Potbelly pig. DOMAIN BACTERIA - Prokaryotic cells DOMAIN ARCHAEA - Prokaryotic cells Domain Eukarya The Eukaryote Kingdoms Species Genus Family Order Class Phylum Kingdom Domain

Ursus americanus (American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia AMERICAN BLACK BEAR CLASSIFICATION Eukarya Panthera tigris, tiger

Panthera onca, jaguar Panthera leo, lion

Panthera pardus, leopard • Wild cats found in genus Panthera. COMMON BLUEGREEN DRAGON CLASSIFICATION

Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Fantastica Order: Fairytalea Family: Dragonae Genus: Draco Species: verdizul

Draco silvanus, bluegreen dragon. Order Family Genus Species Panthera Felidae

Panthera pardus Taxidea Carnivora

Mustelidae Taxidea taxus Lutra Lutra lutra

Canis Canidae

Canis latrans

Canis lupus HUMAN CLASSIFICATION Homo sapiens is the only surviving member of the genus Homo. All others members have gone extinct. Process of Science Scientific method 1. Observe! 2. Make a hypothesis.

• 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. • 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 these hypotheses are testable. Observations

Question

Hypothesis #1: Hypothesis #2: Dead batteries Burnt-out bulb Hypothesis #1: Hypothesis #2: Dead batteries Burnt-out bulb

Prediction: Prediction: Replacing batteries Replacing bulb will fix problem will fix problem

Experimentation Experimentation

Test falsifies hypothesis Test does not falsify hypothesis 3. Test your hypothesis with a controlled! experiment. • The experimental / independent variable is the factor being researched. • The responding / dependent variable is the expected result resulting from exposing the experimental groups to the experimental variable. • A control group is a group who is not exposed to the experimental variable. Controls are used to confirm that changes occurring in the experimental groups are caused by the experimental variable. ! • A well-designed experiment... – uses as many samples as possible to maximize the accuracy of results and minimize natural variation (there will always be weirdos in populations...) – whenever possible, uses as much variability of samples as possible (ex: plant types, animals, chemicals etc...) – Produces results that are accurate and not ambiguous. – is repeatable anytime, anywhere, by anyone. – Minimizes unavoidable experimental error (and so only natural variability can account for unexpected results). EXAMPLE: Growing wheat with fertilizer and legumes

• Some test pots had 45 & 90 kg of nitrogen fertilizer added. • Other pots had a winter wheat / pigeon pea combination. • Legume plants have root nodules that house bacteria. These bacteria take nitrogen from the air and turn it into soil nitrogen, a natural fertilizer much needed by plants.

4. Analysis of results • Results can be quantitative if they involve a measurable quantity (length, mass, number of...) that requires specific units (seconds, meters, moles, milliliters...) • Results can be qualitative if they don’t require measurements. Usually opinions or impressions. • Quantitative results should be tabulated and graphed whenever possible! • The X axis normally shows the independent/experimental variable, and the Y axis normally shows the dependant/ responding variable. • Results: After three years growing, plants grown with pigeon pea produced much more biomass. • Plants grown with artificial fertilizers had an initial burst of growth followed by a decline due to the use-up of fertilizer. • Control plants used up all the soil nutrients after two years. ! 5.! Conclusion • Based on experimental results the hypothesis is accepted or rejected. • Hypotheses backed by large amounts of evidence and widely accepted by the scientific community may become theories that allow for predictions to be made.

• Example of theories: Gravity, Relativity, Plate Tectonics, Evolution, Big Bang, Atomic Theory, Germ Theory... Case Study #1 Mimicry in Snake Populations • Many poisonous species are brightly colored, which warns potential predators. • Mimics are harmless species that closely resemble poisonous species. • Behavioralist Henry Bates hypothesized that this mimicry evolved in harmless species as an evolutionary adaptation that reduces their chances of being eaten. • This hypothesis was tested with the poisonous eastern coral snake and its mimic the nonpoisonous scarlet kingsnake.

Micrurus fulvius Eastern coral snake (above) ! ! ! Lampropeltis triangulum Scarlet kingsnake (right) ! • Both species live in the Carolinas, but the kingsnake is also found in regions without poisonous coral snakes. Scarlet kingsnake (nonpoisonous) Key

Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake

North Carolina Eastern coral snake (poisonous) South Carolina

Scarlet kingsnake (nonpoisonous) ! • Hypothesis: Predators avoid the coral snake’s colors and will prey on other snakes (such as the common brown snake). • Prediction: the colorful kingsnake will be attacked less often in the regions where coral snakes are present, but more often in regions where coral snakes are absent (since kingsnakes stand out more).

Storeria dekayi North American Brown Snake Lampropeltis triangulum Scarlet kingsnake ! • To test this mimicry hypothesis, researchers built hundreds of model snakes: – An experimental group resembling kingsnakes. – A control group resembling plain brown snakes. • Equal numbers of both brown and kingsnake model types were placed at field sites, including areas without poisonous coral snakes.

Artificial kingsnake model placed under a branch. • After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks. • In areas where coral snakes were present brown snake models showed much more claw and bite marks than the kingsnake models. • The data fit the predictions of the mimicry hypothesis: the kingsnakes were attacked less frequently in the geographic region where coral snakes were found, at the expense of the brown snakes.

Brown artificial snake that has been attacked and damaged. RESULTS

100 Artificial kingsnakes 83% 84% Brown 80 artificial snakes 60

40 on artificial snakesartificial on

Percent of total attacks Percenttotal of 20 17% 16%

0 Coral snakes Coral snakes absent present Case Study #2 Mountain bluebird aggression

Sialia currucoides, mountain bluebird ! • Hypothesis: Male aggression against other bluebird pairs varies during the reproductive cycle (after the nest is built, after the first egg is laid, after hatching). ! • To test this aggression hypothesis, researchers... – placed dummy male & female bluebird models close to a few males’ nests. – placed a dummy male robin model close to a few males’ nests. This would act as a control group. • Researchers observed the males, counting the number of approaches (aggressive displays) the males performed towards their dummies.

• Male mountain bluebirds did not show aggression against the control male Robin dummies. • Aggression against male mountain bluebird dummies was more intense than against the female mountain bluebird dummies. • Aggression was most intense before the laying of the first egg.