Test 1 Flashcards
Natural Selection
reproduction of individuals with favorable traits that survive environmental change due to those traits.
3 principles that result in natural selection
most characteristics of organisms are inherited
more offspring are produced than are able to survive, so resources for survival and reproduction are limited causing competition
Offspring vary among each other in regard to their characteristics and those variations are inherited.
genetic diversity comes from two mechanism, _______ and __________
mutation and sexual reproduction
adaptation
a heritable trait that helps an organism’s survival and reproduction in its present environment
divergent evolution
two groups of the same species evolve different traits within those groups in order to accommodate for differing environmental and social pressures.
convergent evolution
similar phenotypes evolve independently in distantly related species due to similar environments
homology
similarity that exists in species due to common ancestry. Includes genetic homology (similar DNA, RNA nucleotide sequences), developmental homology (similar embryotic stages), and structural homology (similar adult form)
phylogenetic tree
branching diagram that depicts ancestor-descendant relationships among taxa
Evidence for evolution
- Life on earth is ancient
- Fossil record shows a change in life over time, including extinctions
- Transitional features document change in traits through time
- Vestigial traits are common.
- Characteristics of populations vary within species and are observed changing.
- Similar species are found in the same geographic area.
- Related species share genetic, developmental, and structural homologies
- Formation of new species from preexisting species can be observed today.
species
individual organisms that interbreed to produce fertile, viable offspring
gene pool
collection of all the gene variants in the species
speciation
formation of 2 species from 1. Can occur in 2 mechanisms: allopatric speciation or sympatric speciation.
Sympatric speciation
Sympatric speciation occurs without a physical barrier to gene flow. This is more common in plant species and usually caused by changes in chromosome numbers
Allopatric speciation
geographic separation of a species causing divergence. Two categories: dispersal and vicariance
Dispersal allopatric speciation
when a few members of a species move to a new area
Vicariance allopatric speciation
a natural situation arises that physically divides organisms of the same species.
Inferences Darwin made
all species have reproductive potential for exponential population growth, but populations tend to remain stable de to limited resources. Since there is natural variation among species and that variation is heritable, adaptation will occur
The modern sythesis
combines darwin’s natural selection with mendels hereditary patterns, as well as particulate transfer (chromosomes) and structure of DNA molecules.
gene pool
total number of alleles for any gene in a population (number of individuals in population x2)
Hardy-Weinburg Theorem
demonstrates that allele frequencies do not change through meiosis alone, only shuffles alleles, doesn’t change proportions. This does not happen in nature. It is a null hypothesis. Assumes no natural selection, large population size, isolated populations, random mating, and no mutation.
Allele frequency
percentage that A and a occurs to add to 100%
micro-evolution
population-scale changes in allele frequencies. Can include natural selection, genetic drift, gene flow, selective mating, and mutation
genetic drift
random changes in allele frequency from gen. to gen. b/c reproductive events are samples of the parent population. This is more pronounced in smaller and more segregated populations as shown through bottleneck and founder effects
founder effect
when a small group of individuals break off from a larger population. These small groups often do not represent full allele distribution.
bottleneck effect
large percent of species dies off leaving reduced allele frequency.
gene flow
mixing of alleles between populations through immigration and emigration
directional selection
phenotypes at one extreme of the range are most successful. (pattern, color, form, metabolic process)
diversifying selection
multiple, but not all, phenotypes are successful. Patchy environments. Population begins to fragment and new species begin to diverge
stabilizing selection
intermediate phenotypes are most successful. (homogenous environments, stable conditions) Range of variation is reduced
preservation of natural variation
diploidy, balanced polymorphism, neutral variation
diploidy
2 alleles for every gene. Even if aa is eliminated, Aa is preserved
balanced polymorphism
heterozygote advantage (sickle cell anemia), frequency dependent selection (when the fitness of a genotype depends on its frequency), and phenotypic variation(multiple morphotypes favored by patchy environment)
neutral variation
genetic variation that has no apparent effect on fitness.
population
a localized group of individuals of one species
fitness
reproductive success (amount of healthy, successful offspring)
Biological species (basic standard definition)
defined by natural reproductive isolation. Individuals that can produce successful offspring are considered the same species. However, cant be used to classify extinct animals and has fuzzy boundaries during divergence.
Morphological species (first way to separate species)
defined by differences in form. however, it doesn’t always work due to convergent evolution and natural phenotypic variation. Only way to classify extinct species.
Phylogenic species
species defined based on evolutionary history. Struggles when there is a lack of fossil record and imperfect agreement on interpretation.
Pre-zygotic barriers
prevent formation of zygote such as: habitat isolation, behavioral isolation, temporal isolation (timing), structural isolation, and chemical isolation.
Post-zygotic barriers
prevent successful development of offspring. Hybrids either do not develop properly, cant reproduce due to lack of sexual maturity or viable gametes, or hybrid lineages fail over time.
How is speciation, genetic drift, and gene flow affected in a small population
speciation is likely to occur more rapidly, more genetic drift, less gene flow.
How does sympatric speciation occur
mutation or selection pressures, errors in meiosis leading to polyploidy, or successful hybrids (mostly plants)
polyploidy
one cause of sympatric speciation when a normally diploid cell acquires one or more additional sets of chromosomes.
endemic species
restricted in distribution to a particular place, generally because they evolved in that place. (only exist in one place)
adaptive raditation
diversification of a group of organisms into forms filling different ecological niches.
macroevolution
large phenotypic changes that result from small changes in regulatory genes
taxonomic hierarchy
domain kingdom division (phylum) class order family genus species/epithet
human taxonomic classification
Domain- eukarya kingdom- animal phylum-chordates class-mammals order-primates family-hominoids genus-homo species- sapiens
what caused humans to diverge from other primates
bi-pedalism and large brain
Carolus Linnaeus
founder of modern taxonomy (defined kingdoms and morphological similarities)
Linnaeus’ taxonomic hierarchy
kingdom (only recognized 2 kingdoms), division, class, order, family, genus, species
5 kingdom system
outdated, developed in 1960s. includes monera, protist, plants, animals, and fungi.
3 domain classification system
used today; divides life into archaea, bacteria, and eukaryote. Kingdoms are defined by monophyletic lineage
features unique to plants
chloroplasts, carbs stored as starch, cell wall of cellulose, cell division by formation of cell plate, plasmodesmata, large central vacuole
4 major groups of plants
mosses, ferns, gymnosperms, and angiosperms.
angiosperms
flowering plants. 90% of earths modern flora.
primary vs. secondary
primary wall is produced first and mostly made of cellulose. secondary walls are interior to primary, are produced later, and are lignified and rigid.
five major plant cell types
parenchyma, collenchyma, sclerenchyma, xylem elements, phloem elements.
Parenchyma
thin primary wall, no secondary wall. Is bulk of plant body and is responsible for many metabolic and storage functions.
Collenchyma
thick primary wall, no secondary wall. Supports growing tissues.
Sclerenchyma
thick lignified secondary wall. Support mature plant parts, often dead at maturity.
Collenchyma vs. Sclerenchyma
both provide structural support and have thick walls. Collenchyma has a thick primary wall with no lignin while Sclerenchyma has thick secondary wall and is lignified.
xylem elements
lignified secondary walls, always dead at maturity (open). function to transport water and nutrients to support the plant. Includes tracheids and vessel elements.
phloem elements
sieve tube members and companion cells. lacks nucleus and ribosomes. function to transport products of metabolism.
4 plant tissue systems
epidermis, vascular, ground, meristem.
epidermis tissue
covers outer surface of all plant. Shoot surfaces (above ground) covered with waxy cuticle. Contains stomata and is usually 1 cell layer
vascular tissue
transports water, solute, and metabolic products. Provides structural support. Includes xylem, phloem, parenchyma, sclerenchyma.
ground tissue
bulk of plant body (pith, cortex, and mesophyll) mostly parenchyma and provides metabolic, structural and storage functions
meristem tissue
actively dividing cells that generate all other cell types. Causes indeterminate growth.
4 classes of angiosperms
paleoherbs, magnoliids, eudicots, monocots
what 2 classes make up about 3% of total angiosperms
paleoherbs and magnoliids
monocot examples
grass, iris, orchids, palms
eudicots examples
broadleaf trees and shrubs, fruits and vegetables, herbaceous flowering plants.
characteristics of monocots
flower parts in mult. of 3, parallel leaf venation, single cotyledon, vascular bundles in a ring in the roots, and vascular bundles in complex arrangement in the stem.
characteristics of eudicots
flower parts in mult. of 4/5, netted leaf venation, 2 cotyledons, vascular tissues in a solid core in the roots, vascular bundles in a ring around stem.
stomata
pores to allow for gas exchange and transpiration
indeterminate primary growth
elongation of stems and roots
indeterminate secondary growth
trees expansion in diameter
why cant leaves and flowers repair damage
they dont exhibit indeterminate growth.
where does dedifferentiation most often occur
in stems and roots to repair damage
auxin-mediated cell expansion
Plant cells elongate irreversibly only when load-bearing bonds in the walls are cleaved. Auxin causes the elongation of stem and coleoptile cells by promoting wall loosening via cleavage of these bonds
apical meristems
cause elongation of roots and stems
axillary meristems
allows for branching
lateral meristems
responsible for secondary growth, or increase in stem diameter. called cambiums
root cap
protects meristem, determines geotropism, and secretes mucigel to enhance nutrient uptake and ease movement. Constantly sheds cells
root hairs
form as the epidermis fully differentiates. increases surface area
primary shoot growth
elongation from the tip
secondary xylem is
wood, annual growth rings are accumulating rings of secondary xylem
bark
all tissues external to vascular cambium. Inner bark functions as secondary phloem and outer bark varies through maturity
cork cambium
meristematic tissue that divides to produce cork cells (cells filled with waxy, waterproof suberin)
