Study Guide to Exam 1 BSC1005

elements of a good scientific study include:

Sample size, Control groups, Placebo effects, Randomization

Sample size

the number of times a measurement is replicated in data collection

Control groups

Groups of participants in a research experiment who do not receive the experimental treatment or intervention.

Placebo effects

The fact that subjects' expectations can lead them to experience some change even though they receive an empty, fake, or ineffectual treatment.

Randomization

a process of randomly assigning subjects to different treatment groups

observational studies

Researchers carefully and systematically observe and record behavior without interfering with behavior.

Randomized control studies

a study in which participants are allocated at random to receive one of several interventions, and one of these interventions is the standard of comparison or control

Bias

a prejudice in favor of something that is usually subconscious.

Pros and Cons of Randomized Controls

Pro: Very good detection of causation and reproducibility

Con: For health studies, the populations may not be like you.

Pros and Cons of Observational Studies

Pro: Big sample sizes are more likely to include people like you.

Con: Self selection and complex analysis make data less reliable

Confirmation bias

where one is more convinced by datathat supports preconceived notions, is likely one of themore prevalent types of bias in science.

Opinions

a belief or judgment that rests on grounds of insufficient fact for completed certainty

Facts

something that actually exists and can be proven true

Hypothesis

A testable prediction, often implied by a theory

Theory

A hypothesis that has been tested with a significant amount of data

Hypothesis Vs. Theory

a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena VS. a tested, well-substantiated, unifying explanation for a set of verified, proven factors.

When the Earth Cooled

approximately 4.5 billion years ago

When Life Arose on Earth

between 4.3 and 3.5 billion years ago

Conditions of Early Earth

There was liquid water, a lot of UV light, no oxygen, a lot of asteroid strikes, no organic molecules, a lot of lightning strikes, and a lots of other gases (methane,hydrogen sulfide, ammonia, carbondioxide, sulfur dioxide)

Life originated in 4 overlapping stages:

1. Nucleotides and amino acids produced prior to the existence of cells

2. Polymerization into larger molecules

3. Polymers became enclosed in membranes, forming protocells.

4. Origin of self-replicating molecules.

Reducing atmosphere hypothesis

Miller and Urey. 1950s. scientists proposed that the atmosphere on early Earth was rich in water vapor, hydrogen gas, methane, and ammonia. along with a lack of oxygen, produce a reducing atmosphere because methane and ammonia readily give up electrons to other molecules, thereby reducing them.

Extraterrestrial hypothesis

From floating space rocks and debris, Carbonaceous chondrite meteorites can contain a lot of organic material

Deep-sea vent hypothesis

Biologically important molecules may have been formed in the temperature gradient between extremely hot vent water and cold ocean water; Also supported by experiments

Polymers

A large compound formed from combinations of many monomers

Protocells

aggregate of pre-biotically produced molecules that acquired a boundary (e.g. lipid bilayer) that allowed it to maintain a distinct internal environment

Why RNA was the most likely candidate for the beginnings of early life

RNA likely was first (RNA world hypothesis)

○ RNA can store genetic information

○ And can replicate

○ And can do chemistry (which DNA can't)

Stromatolites

Large fossilized mounds of cyanobacteria; played a key role in the generation of an oxygenic atmosphere

Effects of The Great Oxygen Event (GOE)

Geological evidence shows O2 levels in oceans rose around 2 Gyr•

• Oxygen gets first bound in minerals, then saturated in the ocean, then allowed to accumulate in the atmosphere

• Resulted in a number of major changes to life on Earth

• Greatly expanded cycling of major elements

• Resulted in the formation of an ozone layer

• Encouraged evolution

• Allowed for endosymbiosis and "higher" life

Evolution

Heritable change in one or more characteristics of a population or species from one generation to the next

Natural Selection

The idea that the traits of the organisms that are best at surviving and reproducing will the be the ones that are most present in the next generation

Example of Natural Selection

EX. birds with adaptations (beak size/shape) that allow them to specialize in eating different foods

Natural selection leads to _______________

adaptations

Adaptations

changes in the traits of an organism that allow it to exploit its environment

Components of Natural Selection

Variation, Inheritance, Varying degrees of reproductive success