BIO 112 Exam 1

Ecology

Interactions among organisms and between organisms and their environment. Affects which individuals survive and reproduce, which in turn results in changes in populations over time.

Evolution

Changes in populations of organisms over time. Affected by interactions with other organisms and the environment. Affects how organisms interact with each other and the environment.

7 characteristics of life

Cells and organization; energy use and metabolism; response to environmental changes; regulation and homeostasis; growth and development; reproduction; biological evolution

Cells and organization

Internal order. Cells are the smallest unit of life (yeast cells (only about 25 um across)). Basic building block for life (what types of cells do we have?).

Energy use and metabolism

Use energy to maintain internal order. Energy is used in chemical reactions ((called metabolism)(where do plants get energy? Where do we get energy?)).

Response to environmental changes

React to environmental changes. Promotes their survival (how do we respond to the environment?).

Regulation and homeostasis

Regulate cells/bodies. Maintain relatively constant internal environment. Homeostasis (not just temperature)

Growth and development

First: Make larger and/or more cells. Second: end up with a set of defined features/characteristics (how/when do humans grow and develop?)

Reproduction

Transmit genetic information to offspring

Biological evolution

Populations of organisms change over many generations. Results in traits that promote survival and reproduction

Scientists group life: Tree of Life

3 domains: bacteria, archaea, eukarya

Eukaryotic divided into:

Plants, animals, fungi, protists

Bacteria

Unicellular (one celled), prokaryotes, many environments, some pathogens

Archaea

Unicellular (one celled), prokaryotes, many are extremophiles

Eukarya

Unicellular (one celled) or multicellular, eukaryotes, plants, animals, fungi, protists

What is science?

A way of knowing; objective, fact/data based, empirical

The Nature of Science

Ways of Knowing used in society: Authority, Belief, Logic, Scientific Inquiry (provides knowledge based on empirical evidence)

Scientific Inquiry

Systematic, objective, fact/data based, empirical

Two general approaches to the Nature of Science

Discovery-based/descriptive, hypothesis-based

Scientific Method/Hypothesis Testing

Observation, hypothesis (a proposed explanation for an observation. Testable, falsifiable, specific), test the hypothesis (experiment), analyze results (summarize, apply statistics), reject or fail to reject a hypothesis (never “PROVE” a hypothesis

Hypothesis

Usually based on an observation. Specific, testable, falsifiable. A proposed explanation. Needs to be tested

Theory

Evolution (how populations change, how we get new specifies), general relativity (has to do with gravity), endosymbiotic theory (where chloroplasts and mitochondria came from). A broad explanation; tested many times; supported many times; makes accurate predictions.

Discovery-based science

Science affects you. Ex.: Drug companies screen thousands of compounds looking for activity. Genetic researchers search through genomes to discover new genes.

Empirical Thought

Relies on observation to form an idea/hypothesis

Evolution recall

A heritable (passed from parent to offspring) change of one or more characteristics in a population from one generation to the next

Darwin

Natural selection. “Fitness): reproductive fitness. Not the first to come up with ideas about organisms changing through time

Lamark

“Inheritance of acquired characteristics.” The proposed mechanism (HOW those species changed) was flawed

Lamarckianism

An early (and incorrect) idea about evolution

The evolution of Darwin’s Theory

Competition among individuals; weaker/less adapted individuals die; well-adapted individuals live, pass on traits. With hunger, starvation, disease only a fraction of any population can survive and reproduce. As landscape changed, organisms adapted or became extinct LONG periods of time are involved. Favorable variations preserved; unfavorable variations destroyed. Descent with modification. First to provide a clear mechanism of evolution.

Grassquit Finch

Sturdy, crushing beaks. Crush seeds and buds of many sizes

Vegetarian Finch

Buds — Vegetarian finches have crushing beaks to pull buds from branches

Tree Finches (Grasping)

Grasping beaks. Pick up insects from trees. Break wood apart to find insects.

Tree Finches (Probing)

Pointed, probing beaks. Search for insect in crevicesarW

Cactus Finches (Probing)

Seeds — Cactus finches have probing beaks to open cactus fruits and take out seeds

Mechanism underlying the changes over time

1. Genetic Variation

2. Natural Selection

Changing Earth

In order to survive, organisms must change. Individuals don’t evolve, populations evolve

Lyell

Geologist. “Uniformitarism.” Old Earthariational Theory.” Provided the foundational deep-time framework that made modern evolutionary biology and Charles Darwin’s theory of natural selection

Variational Theory

All organisms vary

Finches — Small population flies form mainland to island

Breed: Have lots of offspring, offspring vary in beak size.

Limited resources seeds on island are large —>

Birds with big beaks can eat, survive, reproduce

Offspring of larger-beaked birds —>

Tend to have large beaksariatV

Variation

Differences in beak size. Beak is a heritable trait

Natural Selection

Some individuals have traits more suited to the environment, they survive and reproduce

Some traits get passed on and others don’t…

Because some individuals are better able to survive and reproduce than others in a particular environment

Evolution by Natural Selection

The change in relative abundance (frequency) of heritable traits in a population over time. Due to the differential survival and reproduction of individuals within the population in response to environmental pressures

Observations support…

The theory of evolution

Lots of observations from multiple sources:

Fossil record, biogeography, convergent evolution, selective breeding, homologies (anatomical, developmental, molecular)

Fossils

Preserved remains of past life. Bones, shells, leaves, impressions of cells, footprints, burrows

How are fossils formed?

An organism dies, is buried rapidly, hard parts replaced by minerals

What do fossils tell us?

Provide a record of change, transitional forms (how did we get from fish to land vertebrates?)

Tiktaalik fills a gap

Transitional fossil; common misconception: fossil record is “spotty” or “chaotic”; does not record all past life, but it’s still very good to make and test predictions (like looking for a fossil of an intermediate between a fish and a tetrapod)

Fossil record

Documents changes over time. Changes coincide with changes in environment

Biogeography

Study of the geographic distribution of species (both extinct and living (where bio-logy is located on a map)). Provides examples of new species evolving from pre-existing species. Geographical distribution provides information/evidence about evolution.

Convergent evolution

Organisms have similar characteristics (analogous structures) even though they are not closely related. 2 different species from different lineages independently evolved similar characteristics because they occupy similar environments. Evidence of natural selection. given similar environmental conditions/limitations, organisms independently evolve similar, successful strategies (that their most recent common ancestor did not have). Suggests adaptation to the environment. Natural selection

Analogous structures = convergent traits = convergent evolution

Structure/trait that arose independently, two or more times…in species that are not closely related…because those species occupy similar environments (therefore experience similar selective pressures)

Selective breeding

AKA: artificial selection. Humans modify traits in domesticated plants/animals. Natural selection (selective force is nature. Environmental factors affect which individuals survive and reproduce). Artificial selection (selective force is humans. Human/farmer selects which individuals survive and reproduce). A human-driven form of natural selection. Shows changes in populations over time based on who survives and reproduces

Homology

A similarity that occurs between 2 organisms due to descent from a common ancestor. Contrast with analogous structure (a similarity that occurs between 2 organisms due to similar environmental pressures (evolved independently))

Analogues traits/structures

2 species with similar trait/structure. Trait/structure evolved independently in each species. Appear similar because species live in similar environments

Homologous traits/structures

2 species with similar trait/structure. Trait/structure inherited from a common ancestor. Similar because passed on from common ancestor

Homology

Anatomical, developmental, molecular

Anatomical Homologies

Forearms (grasping, walking, flying, swimming), similarities due to common ancestor, differences due to natural selection

Vestigial Structures (anatomical homologies)

Anatomical features with no current function that resemble structures of a common ancestor

Developmental Homologies

Similarities in embryonic development. Ontogeny recapitulates phylogeny.

Molecular Homologies

All living species use DNA to store info. (Almost) all living organisms use glycolysis to break down glucose. Given that all organisms have these features, the features developed early in the evolution of life.

How do you know if 2 traits are analogous or homologous?

Structure, relationship to other features, development, genes/proteins

Darwin’s Finches

Galapogos Islands

Peter and Rosemary Grant

Collected data on the Finches’ beaks

Molecular Biology Basics

DNA (double helix), built from nucleotides (sugar (deoxyribose), phosphate group, base (A, T, G, C), deoxyribonucleic acid

A, T, G, C Pairing

A with T, G with C

Why is DNA important?

Carries genetic code (sequence of A, T, G, C), unique for every person (except identical twins), codes for proteins, passes genetic information on from parent to offspring

What is DNA and where is it found?

Humans have 23 pairs of chromosomes and 46 total chromosomes. Single strand of DNA wrapped around proteins makes DNA shorter, more compact.

Nucleotides

Building blocks of DNA

1 DNA molecule wraps around proteins…

Forms chromosome2

3 chromosomes…

Contain all genetic information for humans. = genome

Genes

A sequence of DNA (a combination of A’s, T’s, G’s, C’s. Usually codes for a protein. Humans have 19,599 protein-coding genes (confirmed; possibly 2,188 more). Different versions of the same gene = alleles

Proteins

Macromolecules. Made up of amino acids (aa’s are the building blocks of proteins). Link aa’s in a certain order, get a protein of specific size, shape

What do proteins do?

Involved in gene expression (DNA polymerase, RNA polymerase), initiate movement (myosin in muscles), defense (antibodies), metabolism (breaking food down), cell communication (taste receptors in tongue), structure (collagen), transport (create channels for molecules to move in/out of cells)

How many copies of each gene do we have?

2 (1 from mom, 1 from dad) = diploid

Locus

The physical location of a gene on a chromosome

Recessive

Need 2 copies to show the trait

Dominant

Need 1 copy to show the trait

Genotype

Combination of 2 alleles. Homozygous Dominant (AA), Homozygous Recessive (aa), Heterozygous Recessive (aa)

Phenotype

Recessive, dominant, dominant

2 processes involve DNA replication

Mitosis, meiosisMi

Mitosis

Cell replication, end with 2 genetically identical cells, each with 2 copies of each chromosome, body cells (growth, wound healing, cell replacement)

Meiosis

Make sex cells = gametes, end with 4 genetically unique cells, each with 1 copy of each chromosome, occurs in gonads (testes, ovaries)

What is a population?

A group of individuals of the same species…occupying the same space/environment…that can interbreed

Microevolution

Changes in allele frequencies in a population from 1 generation to the next. “Micro” = small changes in allele frequencies over relatively short time spans

Macroevolution

Large changes in allele frequencies over geological time period. “Macro” = large change over long time spans. Result of microevolution occurring over and over again through time. Results in new species

Four-O’clock Plants

Flowers open from late afternoon onwards, have a strong, sweet-smelling fragrance, flowers are used in food coloring, leaves may be eaten cooked, seeds are poisonous

Color controlled by 2 alleles C^R and C^W (four-o’clock plants)

C^RC^R = Red Flowers. C^RC^W = Pink Flowers. C^WC^W = White Flowers. Incomplete dominance

Allele frequency

How often do I see allele C^W relative to all the alleles present?

Genotype frequency

How often do I see genotype C^WC^W relative to all the genotypes present?

Genotype frequency equation

Number of all individuals with specific genotype in population / Total number of individuals in a population

Allele frequency

Number of copies of a specific allele in population / Total number of all alleles for that gene in a population. p + q = 100%

Hardy-Weinberg equilibrium

Describes relationship between allele and genotype frequencies (in a population that is not evolving). p²+2pq+q² = 100%

p²

Homozygous dominant

q²

Homozygous recessive

2pq

Heterozygotes