BIO 173 Exam #2 Review: Key Concepts in Biology

Mean (average)

the average; add all values and divide by the number of individuals

Variance

for every value, find the difference between it and the mean & square it. Divide the "sum of the squares" by sample size minus one (the "degrees of freedom")

Standard deviation

square root of variance

Normal curve

~68% of individual values fall within 1 SD of the mean; ~95% of individual values fall within 2 SD of the mean; ~99.7% of the individual values fall within 3 SD of the mean

T-score

a value that reflects how different two means are based on the difference between them and the standard deviations and sample sizes of the populations they are based on

P-value

The probability that two means could draw from the same population, given a T-score and sample size; or, the probability that the difference seen is due to random variation in sampling; or, the probability that two means are not significantly different.

Lower p-value means a greater likelihood that the difference is a true difference

We will take p<0.05 to be a significant result (i.e., a true difference)

Why we use statistics in biology

To look at differences between groups:

We can take group averages, but variation within the group may exceed the difference between groups

Can look at variation and makes an estimate for how likely it is for means to be significantly different given the range in each group

What we can do with significant results:

Make an interpretation, hypothesize a cause or mechanism

Implications of the result, what's next in the research

How to use T-score to get p-value

T-score is matrixed with combined degrees of freedom to get the p-value

Significant result

When the p-value is less than 0.05

What a significant result tells us

Greater likelihood that the difference is a true difference (i.e., only a 1% probability of unrepresentative sample)

Ecological diversity

the variation in both terrestrial and aquatic ecosystems

Community composition

the specific arrangement and diversity of species within a biological community

Competition

Interaction between organisms in which both require 1+ resources that are in limited supply. Both parties are negatively affected.

Interspecific Competition

-/-, in between members of different species

Intraspecific Competition

-/-, in between members of the same species

Interference

2 members compete by interacting directly with each other

Exploitative

2 members interact indirectly by fighting for resources

Mutualism

+/+

Commensalism

+/0

Amensalism

-/0

Neutralism

0/0

Predation/Parasitism

+/-

Independent variable

variable that is changed and affects the dependent variable. On the x-axis.

Dependent variable

variable that is affected by changes in the independent variable. On the y-axis.

Positive control

a variable that should have a specific effect

Negative control

a variable that should have no effect

Hypothesis testing

testing an observation to see if experiment results support that observation. Possible explanation that leads to a testable prediction and motivated experiments; based on cause and effect and observations. The hypothesis must be falsifiable.

Null hypothesis

a statement that assumes no relationship or no difference between 2 variables

De Wit Replacement Series

used to study interference in plants (see above). We change the concentration to see how they are interacting.

Interpreting a De Wit Series

below the 1:1 line = interspecific competition is stronger than intraspecific competition.

Monoculture

only having a single crop in a given area

Mixed culture

having multiple crops in a given area

Destructive Sampling

any procedure that causes a permanent change to a specimen. In our case, this means cutting the plant at the soil line.

Strengths of Plant Experiment

We had a lot of pots of the different plants and utilized a de Wit series well. Lots of replicates.

Weaknesses of Plant Experiment

The plants may have not been exact replicates of each other in terms of growing conditions. They weren't all in the exact same place of the greenhouse. No standardized version of measuring - caused errors in some data.

Evolution

Descent with modification and also a change in the genetic composition of a population over time. It refers to the pattern of evolutionary change over time and a process (the mechanisms that cause the observed changes).

Natural selection

The cause of adaptive evolution; individuals with certain inherited traits will survive AND reproduce at higher rates than others. In other words, change in population over time based on reproductive success and trait inheritance.

Adaptation

To adjust so that you can survive conditions.

Adaptive Evolution

Organisms that adapt better will evolve and pass these traits onto the future generations.

Speciation

Species change as time goes on and as organisms evolve and reproduce; lineages split and diverge.

A group within a species separates from other members of its species and develops its own unique characteristics. Could be due to the demands of a different environment.

Microevolution

Species change from one generation to the next.

Macroevolution

Radically new life-forms derive from older forms over time.

Unity of Life

organisms share many characteristics of their ancestors.

Diversity of Life

From descent with modification over long periods of time.

Phylogeny

the evolutionary history of a species or a group of species.

Evolutionary Tree

a hypothesis about evolutionary relationships. Shows patterns of descent, not phenotypic similarities. Branch points represent the common ancestor. Time proceeds from left to right. Root = oldest ancestor. Branch points (nodes) represent the common ancestor. Transitions = evolutionary modifications. Lineages that share more recent common ancestors are considered more closely related.

Shared Characteristics

Ancestral characteristic: originated in an ancestor; Derived characteristic: evolutionary novelty unique to a particular clade or species.

Classification

Define and describe organism; Arrange organisms into a classification scheme.

Kingdom Phylum Class Order Family Genus Species

"Kings Play Chess On Fine Green Sand"

Taxonomy

The scientific classification and naming of organisms. Common vs. scientific names. Does not reflect evolutionary history.

Dichotomous Key

Taxonomical key; a series of paired choices.

Biodiversity

The variety of life in the world or in a particular habitat or ecosystem. Life comes in many forms and there are a lot of different species.

Biodiversity: Habitat diversity

The difference between habitats, which can include grassland, forest, alpine, etc.

Biodiversity: Species diversity (richness)

number of species present.

Biodiversity: Species diversity (evenness)

relative proportion of species.

Biodiversity: Species diversity (as a whole)

Number and kind of species present. More even = more diverse (no dominant species).

Biodiversity: Genetic diversity

The collection of genes present within a species and between species.

Within a species: low diversity → species vulnerable

Between species: in the microbiome, diversity of genes more than diversity of species means many different foods can be digested

Importance of genetic diversity:

The importance of genetic diversity is that within species, low diversity makes the species vulnerable. Between species, diversity allows for different processes to occur.

Biogeography

The pattern of species distribution both worldwide and local. Includes history of species distribution. Continental drift is vital to understanding. Climate affects this both historically & locally. Earth has been hotter and cooler. Latitude and topography influence climate. Winds and currents change as land moves. Human-aided invasions can disrupt natural ecology.

Wallace's line

the clear difference in animal species assemblages over a relatively short distance between Indonesia/Borneo and Australia/New Guinea. It is due to the recent coming together of Eurasian and Australian tectonic plates.

Assemblage

Similar range for a variety of taxa.

Museum cultures

They provide a record of biodiversity and biogeography. The key to this is time, which allows us to detect change (environmental + climate change, loss of biodiversity, emergence of pathogens and disease).

Larger factors that influence the range of a species

Temperature, humidity, soil chemistry, pH, salinity, and oxygen levels.

Changes in biogeography from human activity

Disrupt natural ecology by introducing invasive species.

Descent with modification

Passing traits from parent to offspring, where modifications can occur, part of Darwin's theory of evolution.

Intellectual context

The circumstances that determine, specify, or clarify the meaning of an event.

Geology

The field that studies the earth's physical structure and substance, its history, and the processes that act on it.

Paleontology

The field that studies fossil animals and plants.

Heritable variation

Leads to differential reproduction leads to change in population over time (natural selection), which leads to speciation (common ancestry, shared lineage)

Causes of extinction

Overhunting/overharvesting, introduction of nonnative species, and habitat degradation/loss.

Ages of Life

Different geological era that are defined by geochemical features and the dominant plants and animals of the era (you figure this out by looking at the fossils)

- Atmospheric composition and temperature

- Level of biological complexity

- Developmental programs

- Dominance of species (marine vs. terrestrial, animal vs. plant)

- Events that mark an end of an era

Main stages: Archean (earth formed 4.6 billion years ago), Proterozoic, Paleozoic, Mesozoic, and Cenozoic.

Law of Succession

Animals that currently inhabit an area will show a resemblance to the fossils in the same area.

Transitional Forms

A species that is intermediate between two different species.

Homologous structures

Similar physical features in organisms that share a common ancestor, serving different functions. Examples are limbs of humans, cats, whales, and bats.

How Do We Move?

Animals have different length limbs, no limbs, fins, etc. at all adapted to the environment that they live in to help them move.

Convergent Evolution

Organisms that aren't closely related evolve similar features or behaviors as solutions to the same problems. The process can result in matching body shapes, color patterns or abilities.

Vestigial structures

Features of an organism that have lost much or all of their original function through evolution. Example is the human appendix.

Sexual dimorphism

Systematic difference in form between individuals of different sex in the same species. Example is that in some species the males are larger than the females.

Molecular homology

Compares similarities in the sequences of molecules to determine evolutionary relationships between organisms.

Natural Selection

Change in population over time based on who is able to reproduce and pass down their traits. Affects the entire population of a species and results in a large amount of biological diversity.

Artificial Selection

Only affects selected individuals, bringing desirable changes and traits, decreasing genetic diversity. Examples are wolves to domesticated dogs we have today.

Teeth analysis

Can indicate age, sex, health status, and diet of an individual.