Only $2.99/month

Biology 311D Final Exam Study Guide

Terms in this set (111)

- The pattern of inheriting characteristics that follows the laws formulated by Gregor Mendel
- Punnett Square: predict the ratio of offspring genotypes and phenotypes when given info about parental phenotypes and the dominance pattern
- Chiasma: the crossing over point where breaking of chromatids happen
- Phenotypes: appearance of genetic composition
- True Breeding Parents: homozygous, offspring are always going to have the same offspring bc of a homozygous dominant trait (P generation)
- F1 generation is the offspring of P generation, the offspring self/cross pollinated and made F2 generation
- Law of Segregation: 2 alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
- Diploid cell: an organism inherits 2 copies (2 alleles) of a gene, one from each parent
EX: if a cell is 2n=8...diploid
after S: 2n=8 (replicated)... diploid
after MI: n=4 (replicated)... haploid
after MII: N=4 (normal chromosomes)... haploid

- Gamete: sex cell, egg/sperm, gets only one of the 2 alleles that are present in somatic cells of the organism making the gamete
- Genotype: allele genetics of an organism\
- Law of Independent Assortment: 2 or more genes assort independently, each pair of alleles segregates independently of any other pair during gamete formation
- Allele: version of a gene

Mendelian genetics:
- meiosis explains laws of allele segregation: separation of homologs during anaphase 1 accounts for the segregation of the 2 alleles of a gene into separate gamete; each haploid gamete gets only one allele of each gene
- meiosis explains independent assortment: random arrangement of chromosome pairs at metaphase 1 accounts for independent assortment of the allele for 2 or more genes located on different homologous pairs. The destination of one allele is independent from one of the other alleles

- Sex-linked genetics: pattern of inheritance from that produced by genes located on autosomes
- Dominant alleles: both dominant homozygotes and heterozygotes show the disorder (ex: achondroplasia, Huntington's disease)
- Recessive alleles: disorder shows up only in people that are homozygous for the recessive allele (ex: Cystic fibrosis, sickle-cell disease)
- Complete dominance: the phenotypes of the heterozygote and the dominant homozygote in F1 hybrids are indistinguishable
- Incomplete dominance: F1 hybrids have a phenotype somewhere between those of the 2 parental varieties
- Co-dominance: the 2 alleles each affect the phenotype in separate, distinguishable ways
- Epistasis: the phenotypic expression of a gene at one locus alters that of a gene at a second locus
- Polygenic inheritance: when 2 or more genes have an additive effect on a single phenotypic character

homozygous recessive= aa, bb
homozygous dominant= AA
heterozygous= Aa, Bb
- Each allele codes for a version of a protein (allele NOT= gene NOT= allele)
- the enzyme that codes for the recessive gene is not functional
EX: albinism in humans occurs when both allele at a locus produce defective enzymes in the biochemical pathway leading to melanin
Natural Selection: process of differential survival and reproduction
- occurs when, due to genotype, some individuals have phenotypes better suited to their environment (better adapted)
- more likely to survive and reproduce
- over time, as better-suited individuals in each generation have offspring, the allele frequencies can change

Microevolution: allele frequencies changing from generation to generation
Population: group of individuals of the same species living in the same area that can interbreed and produce fertile offspring
- genetic makeup can be characterized by its gene pool, every copy of every type pf allele at every locus for all the members of a population

Directional Selection: shifts the overall makeup of the population by favoring variants that are at one extreme of the distribution
Disruptive Selection: favors variant at both ends of the distribution
Stabilizing Selection: removes extreme variants from the population and preserves intermediate types

Evolution
- Adaptation: an inherited characteristic that enhances an organism's survival and reproduction
- Darwin discussed descent with modification in which shared ancestry and an accumulation of difference over time resulted in a changing population
-Adaptive Evolution: evolution by natural selection; as long as there us genetic variation in a population, some members of the population will be better adapted for their environment and can pass that on to their offspring

INDIVIDUALS DO NOT EVOLVE: populations evolve over time as certain individuals live and reproduce or die

Allele Frequencies:
- for a gene/ locus with 2 alleles, "p" is often used to represent the frequency of 1 allele, while q represents the frequency of the other allele
- if a locus has more than 2 alleles, the frequencies of all of them must still add up to 100% or 1

Hardy-Weinburg Equation: p^2 + pq + q^2 =1

Genetic Drift
Gene flow
Describe the evolution of animals in the ocean from a single-celled common ancestor and how diversity in animals increased dramatically in the Cambrian (possibly due to evolution of predator and prey adaptations, or to the rise in O2 or to the evolution of new regulatory genes like Hox, or maybe all three!). Describe some features that allowed some lineages (like insects ortetrapods)to transition and diversify on land.
In general terms describe the trends of evolution in the hominin lineage and describe when and where our own species evolved.

Cambrian Explosion: Period of time during the Cambrian period (535-525 MYA) in which there was a rapid increase in the diversity of large animals
- most of the fossils recovered from the period belonged to bilaterians, whose members are bilaterally symmetric (like us) and have complete digestive traits

Hypothesis 1: Predators started acquiring adaptations for hunting, like claw, which led to prey species developing defenses, like hard shells (natural selection) - new predator/ prey relationships caused a decline in soft-blooded pre-Cambrian species
Hypothesis 2: Before the Cambrian explosion, there was a great increase in atmospheric oxygen
- this enabled animals w/ larger body sizes and higher metabolic rates to survive, and harmed those species who did not have these things
Hypothesis 3: the origin of Hox genes and other genetic changes that affected the regulation of development genes allowed for the evolution of new body forms

Hominin Evolution:
Hominin: the group of closely-related humans and extinct species
Describe the process of homeostasis, including the role of negative feedback.
Give brief examples of how the nervous system and endocrine system allow for coordination and control of animal bodies.

Tissues and organ systems need to work together in an animal's body meaning they need to be coordinated and controlled
1. Endocrine System: signaling molecules (hormones) released into the bloodstream by endocrine cells are carried to all locations in the body
- receptor cells respond to endocrine stimulus
- cell-surface receptors (for non lipid-soluble hormones) - hormones-receptors interaction will trigger changes at the plasma membrane that will be converted into a cellular response (signal transduction pathway)
- cytosolic receptors (lipid-soluble hormones) - hormone-receptor complex moves from the cytosol into the nucleus where it alters transcription of particular genes

2. Nervous System: nerve signal travels along neuron axons to the target cells (the ones that are connected with axons). It involves 2 types of signals:
1. Electrical Signal: change in voltage along axons
2. Chemical Signal: btwn neurons and neurons and target cells

Homeostasis: the capability of animals to maintain a relatively constant internal environment even when the external environment changes significantly
- animals that control their internal state and keep it constant independently from external fluctuations are called regulator (vs conformer - they change their internal state in accordance w/ the external environment)
- internal physical and chemical properties are generally maintained w/in a range of values or around a specific value (set point)
- set points and normal ranges for homeostasis are usually stable, however there can be changes associated to life stage (change in hormone balance during puberty) and some fluctuate cyclically (female hormone responsible flor menstrual cycle)

Negative Feedback: occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances
Ex: insulin released if blood sugar rises. insulin triggers liver to take up glucose
Compare and contrast the pathways by which animals and plants respond to external stimuli.
Describe innate and adaptive immunity, including the role of B cells and T cells recognizing unique pathogens and responding to them (and "remembering" them) after clonal selection.

"Etiolation" - morphological adaptations from growing in the dark
- common in plants that sprout underground
- small leaves
- focus on elongation of stems

"De-etiolation" - greening response once shoot reaches sunlight
- leaves expand
- stem elongation slows down
- roots start to elongate
- shoots and leaves produce chlorophyll

Animals Response to Stimuli:
Neurons: specialized cell for transmitting electrical signal (membrane potential)
- inside neuron has negative charge, K+ ions
- outside neuron has positive charge, Na+ ions
- difference between inside and outside charge is the resting potential
Depolarization of membrane: when this charge difference is reduced

Innate Immunity:
Cellular Innate Defenses
- toll- like receptors (TLRs) - toll describes characteristics fragments found on many pathogens
- Ex: TLR 3 binds dsDNA of viruses, TLR 4 binds lipopoly saccharides on bacteria
Phagocytic cells
- Neutrophils - infected tissue signals, then neutrophils move from blood to engulf pathogen
- Macrophages - larger phagocytic cells

Adaptive Immunity:
Pathogen - specific recognition also immune "memory"
- Lymphocytes (type of white blood cell) - Tcells and B cells
Antigen: any substance that elicits a B or T cell response
- B or T cells binds to an antigen via its antigen receptor
- recognizes the bacterial or viral protein
T cells: Lymphocytes migrate from bone marrow to the thymus, mature into T cells
B cells: Lymphocytes stay in bone marrow and mature into B cells
Explain interspecific interactions and trophic levels. Explain how atrophic cascade can occur if a keystone species is removed from an ecosystem
Use the concept of an ecological niche to explain "competitive exclusion" and "resource partitioning".

Interspecific Interactions:
Competition: 2 members of different species compete for the same limiting resource (-/-)
- Competitive Exclusion: 2 species competing for the same resource can't permanently coexist in the same place
- Resource Partitioning: as long as at least 1 significant difference btwn 2 niches arises, 2 species w/ similar niches will be able to coexist
Exploitation: 1 species benefits by feeding on another species (+/-)
- predation: killing and eating a member of a different species
- parasitism: 1 organism gets nourishment from another organism that is harmed in the process
Positive Interactions: at least one organism benefits and neither is harmed (+/+) or (+/0)
- includes mutualism (both benefits) and commensalism (one benefits)

Trophic Levels: describes the feeding relationships of its organisms, most commonly represented by a food chain or groups of food chains called a food web
- both describe the transfer of energy from the primary producers all the way up to tertiary and quaternary consumers
- less energy is available as you move through the trophic levels- that's why plants are more numerous than carnivores- you don't see oceans overrun w/ giant sperm whales

Keystone species removed/ disappeared from the ecosystem=
- no other species would be able to fill its ecological niche
- the ecosystem would be forced to radically change, allowing new and possibly invasive species to populate the habitat.
Biological Diversity - variety of life on Earth

THREE LEVELS OF BIODIVERSITY:
Genetic Diversity: genetic variation w/in a population and between populations; extinction of a population decreases the genetic diversity of a species > less variation for adaptations and evolution

Species Diversity: number of species in an ecosystem or across the biosphere; interest in endangered species and threatened species (likely to become endangered in near future)

Ecosystem Diversity: variety of ecosystem on Earth; the local extinction of one species can have a negative impact on other species in the ecosystem

- human activities impact biodiversity and the effects can be local, regional, global

HUMAN ACTIVITIES IMPOACT ECOSYSTEMS -

Habitat loss:
- reduction or disappearance of natural habitats because of agriculture, urbanization, forestry, mining, pollution
- it can occur as:
- habitat destruction: a habitat is destroyed and not able to support its native species
- habitat fragmentation: a habitat is split into smaller pieces limiting capability of species to move and reducing their ranges
- it can lead to species displacement or species extinction if no alternative habitat is available or a species is not able to move

Overharvesting:
- harvesting of wild species at rates that exceed ability of populations to rebound or species reproductive rate
- outcome of exponential increase in human population and in the use of sophisticated tools
- can cause extinction of a local population or extinction of the whole species

Introduced Species:
- intentionally or accidentally (by ships, airplanes) introduction of non-native species in a new area by humans
- can spread rapidly because not subject to same parasitism or predation pressure at native species
- competition for resources with native species or predation on native species may lead to reduction/extinction of the latter

Nutrient Enrichment:
- addition of nutrients in the environment as a result of farming and agricultural activities (waste products and fertilizers)
- Negative effects on ecosystems when nutrient levels exceed the critical load - amount of nutrients that can be used by organisms w/out damages on ecosystems
- can cause extinction of a local population or extinction of the whole species

Toxin release:
- introduction in the environment of chemical compounds (synthetic compounds, pharmaceuticals)
- can have negative effects on organisms (endocrine system disruptor)
- accumulate in organisms' tissues and undergo biological magnification (increases of toxin concentrations as we move up in the trophic chain)

Global Change:
- changes in the Earth's ecosystems and processes that govern the biospheres functioning
- result of many human activities such as emission of greenhouse gases, deforestation, introduction of toxins, pollution, etc... that affect the biosphere at a global scale
*Climate Change: one of the ongoing global changes: its the result of emission of greenhouse gases in the atmosphere and deforestation
- increase in global temperature
- changes in wind and rain patterns
- increase in severe weather events (drought, storms)
- melting of ice
- ocean acidification

EFFECTS ON CLIMATE CHANGE:
Cellular level:
- alteration of key cellular process (enzymatic rates, cell division)
Organism level:
- heat stress on plants and animals: physiological and metabolic effects
- low resistance to diseases and pathogens
- shift in timing of migration. reproduction, blooming
Population level:
- effects on survival and reproductive success
- changes in population's size
Community and ecosystem level:
- shift in geographical ranges of species
- habitat loss (ex: melting of ice in Artic regions)
- disruption of food webs and ecosystem's dynamics

CONSERVATION EFFORTS -
- efforts with the goal of protecting ecosystems and species diversity and maintaining/restoring habitats
- balance between science, technology, economy and society
-applied to different levels - form single species to ecosystems

Population Conservation: aims at safeguarding small populations or declining populations
- Small-population approach focuses on the processes that bring a small population to extinction ("extinction vortex"): efforts aim at increasing genetic diversity of a population
- Declining-population approach studies the environmental factors that cause the decline of a population and aims at restoring the species habitat

Ecosystem Conservation: aims at protecting communities and their physical environment
- Movement Corridors: connections between fragmented habitats
- allow species to cross barriers made by humans
- increase species dispersal and reduce inbreeding
- Protected Areas: areas of ecological and natural value, often hotspots of biodiversity
- zoned reserves: region with pristine areas surrounded by areas subject to human activities which don't harm core protected areas

IMPORTANCE OF BIODIVERSITY CONSERVATION:
- moral value: Earth is our home and we're connected to nature and species surrounding us
- interest in protecting single species w/ economical or medical value
- Ecosystems sustain human's life
- purify air and water
- detoxify and decompose wastes
- provide food, fuels, energy, and materials used in daily life
- cycle nutrients and maintain the soil
- regulate climate
- Ecosystem Services: all the processes mediated by ecosystems and the benefits that humans receive from the nature
- couldn't live without them