Levels of Organization Flashcards
What are genes?
- Sections of DNA that code for a particular trait
- A specific sequence of nucleotides (nt) making up a DNA molecule
- Nt sequence “codes” for a specific trait similar to how 1s and 0s can be used for analogical reasoning
- Chromosomes are exceptionally long pieces of DNA that contain 100s and 1000s of genes
What’s in your genes?
- Humans have ~22k genes composed of coding DNA
- DNA is a polymer built of monomer subunits and is double-stranded and helical = “double helix”
- DNA quantity varies considerably among species
> Humans have ~3 billion base pairs (~3 Gbp)
+ Base pairs = nucleotides in one strand
+ That means we have 6 billion nucleotides total
> Humans have 23 pairs (sets) of chromosomes
+ Diploid (2n) - inherit one set from each parent
+ 23 from mom + 23 from dad = 46 total - Also have mtDNA we inherit exclusively from mom
Character
- A heritable feature (i.e. flower color)
- Similar to phenotype (physical appearance)
Trait
A variant of a character (ie: purple flower)
Locus (loci)
A specific location on a chromosome where a gene is located
Alleles
Different versions of the same genre (blue eyes vs brown eyes)
Genotype
The genetic makeup of an organism (PP, Pp, or pp)
Alleles
- alternative versions of the same gene
> inherited characters that account for variation
Gregor Mendel
- Austrian monk
- Failed teaching exams
- Sent to study various, random subjects, including botany and math
- Documented a particular mechanism of inheritance (completed dominance) with experiments using common garden peas
- Identified two fundamental laws of inheritance
> independent assortment
> segregation - discovered the basic principles of heredity
Mendel’s Experiments
- Mendel manually cross-pollinated plants to control mating
- Worked with thousands of plants over a period of eight years
- Analyzed seven characteristics
> seed shape and color
> flower color and position
> pod shape and color
> stem length
Complete Dominance (aka Mendelian Inheritance)
- Occurs when the phenotypes of the heterozygote and dominant homozygote are identical
> presence of a single dominant allele produces FULL dominant phenotype
+ like purple pea flowers
Codominance
- 2 dominant alleles affect the phenotype in separate, but distinguishable, ways
- Human blood type
Incomplete Dominance
- The phenotypes F_1 hybrids is somewhere between the phenotypes of the 2 parental varieties
- 3 phenotypes are seen usually
Dominant and recessive alleles do not really “interact” which can lead to…
…synthesis of different proteins that produce a phenotype
Frequency of dominant alleles
- are not necessarily more common than recessive alleles
> is population dependent
Ecology
- The study of the interactions between organisms and their biological and physical environment
- Environment:
> Biological = “biotic” or living things
> Physical = “abiotic” or non-living things
Natural History and Life History
Observational study of plants and animals in their natural environment and their reproduction
Environmental science
The study of the impact of humans on the environment and human impacts on them
Resource Management Sciences
- Management and husbandry (usually resources important for human use)
- Wildlife management
- Forestry
- Range management
- Fisheries biology
Life’s fundamental characteristic is having a […]
[high degree of order or organization]
Biological organization is based on a […]
[hierarchy of structural levels]
Novel properties emerge at each step upward in the […]
[biological hierarchy]
- A cell is more than a bag of molecules
- The whole is greater than the sum of its parts
[…] often encompasses several levels of organization
[Ecology]
Organismal Ecology
Interactions between individuals and their environment
- physiological ecology
- behavioral ecology
Population Ecology
Dynamics of a group of individuals of a single species
- Population genetics, demography
Community ecology
Interactions among groups of coexisting species
Ecosystem ecology
Interactions between ecological communities and their abiotic environment
Ecosphere or Biosphere
Sum of all Earth’s ecosystems
Ecological Networks
- Visual representation of interactions in an ecosystem
- Species are represented by nodes
- Connected by pairwise interactions (links)
- Can get very complex, quickly
[…] is key in ecology
[Interaction]
Proximate Causes
- Direct effects of external stimuli; direct, immediate causes
> e.g. climate, temperature, and photoperiod (day length)
Ultimate Causes
- Evolutionary factors that led to appearance of certain traits
> e.g. natural selective pressure from predation, sexual selection pressure by mate preference
Ecology-Evolution Connection
- Ecosystems are a product of evolution of species
- Adaptation and evolutionary fitness drive selection pressure
Ecological systems are often not in […]
[equilibrium]
- no “stable/permanent ecological homeostasis” or “balance of nature”
- both equilibrium and non-equilibrium ecological processes are important
Ecology is a […] science
[quantitative]
Evolution
- Defined as a hypothesis that has been repeatedly tested and not yet falsified
- Broad in scope and supported by a LARGE body of evidence
- Universally accepted among scientists, however, they can still be disproven
- Constantly being challenged, tested, and modified as new information as new information is obtained (and this is where their strengths are!)
First Hypothesis: All present life is related through […] from a common ancestor in past evolution
[“descent with modification”]
Second Hypothesis: […] (differential reproductive success) is an extremely important mechanism for evolution
[Natural selection]
Observation: […] variation exists in most species
[Heritable]
[…] is not THE only mechanism for evolution; however it was the first proposed and it is still the most explanatory hypothesis for why things change over time
[Natural selection]
Observation: All species produce more […] than the environment can support, meaning many, many […] die before maturity
[offspring] [offspring]
Inference #1: Differential reproductive success among individuals, those with “best” traits, help them […] and […] in their environment, thus, leave more offspring than others
[survive] [reproduce]
Inference #2: Those heritable, favorable traits, called […], accumulate over time, matching the species to its current environment
[adaptation]
Evolution via Natural Selection
Darwin (and Wallace) proposed natural selection as their mechanism for evolutionary adaptation of populations to their environment
Mechanisms that change allele frequencies:
- Genetic drift (or drift)
- Mutations
- Gene flow
- Non-random mating
Genetic Drift
- Random, can simply be considered a sampling error
- Change in frequencies resulting from a sharp decline or bottleneck in population size
- Founder effect: when only a few individuals form a large population move to a new area
Mutations
- Novel alleles arise by mutations, or any change in a DNA
- New “mutant” alleles change the frequencies in a population
- Can be spontaneous or induced by mutagens
Gene Flow
- Involves the movement of alleles into or out of a population
- Can be the movement of individual organisms or their gametes (egg/sperm, pollen)
- Organisms and gametes that enter a population may have new alleles or may bring in existing alleles but in different proportions that those already in a population
- Is usually a very strong mechanism of evolution
Random Mating
- For allele frequencies to stay the same, all alleles must have the same probability of entering the next generation
Non-Random Mating
- Can occur in two ways:
> Assortative mating: preference for mates with similar genotypes or phenotypes
> Disassortative mating: preferences for mates with different genotypes or phenotypes
Genetic mutations lead to […] among individuals in a population (new alleles/combos)
[variation]
Some individuals pass their […] on to their offspring
[alleles]
In each generation, certain individuals are more […] at surviving AND reproducing
[“successful”]
The individuals that are more “successful” at surviving AND reproducing have alleles/combos that confer adaptation to their […] environment
[current]
