Exam 4 Flashcards
phylogenetic trees can be based on:
morphological traits, DNA, protein sequences
Occam’s Razor
the simplest solution is probably the best one (parsimony)
monophyletic group
group in which all species share the same common ancestor and all of the descendants of that ancestor are in the group
paraphyletic group
group in which all species share the same common ancestor but do not include all species descended from that common ancestor
why use phylogenies?
management (fungicides, rotate crop species, bury plant debris), treatment of disease, forensics, species recognition and biodiversity
asexual reproduction: mitotic
simple life cycles where policy stays the same (possibly with asexual reproductive structures), eukaryotic organisms only go through mitosis and no meiosis or fertilization
sexual reproduction: meiotic
complex life cycles with haploid (N) and diploid (2N) stages and specialized reproductive cells, gametic and sporic life cycles
sexual reproduction: sporic life cycle
all land plants and some algae, meiosis and fertilization, mitosis in both the haploid and diploid stages (N and 2N)
sexual reproduction: gametic life cycle
most animals and some algae, meiosis and fertilization, no mitosis in the haploid stage, all cells except gametes are diploid (mostly 2N), mitosis: 2N
parts of a flower
ather (stamen) - male parts
perianth - attracts pollinators
stigma (pistil) - female parts
hermaphroditic
flowers with both stamens and pistils
not hermaphrodites
some flowers have either stamens of pistils
both on one plant: monoecious
on separate plants: dioecious
costs of self pollination
inbreeding depression, reduction in fitness due to expression of rare, deleterious recessive alleles in homozygotes
benefits of self pollination
reproductive assurance
mechanisms to avoid inbreeding
self incompatibility (pollen can be blocked at the stigma surface and during growth to ovule), timing of pollen shedding or stigma receptivity, flower shape, dioecy
wind pollination
how most plants are pollinated, a lot of energy to produce enough pollen for wind pollination
animal pollination
most flowering plants are animal pollinated, attract multiple pollinators, and are generalists
pollinators are typically seeking a reward
nectar (sugar/amino acids), oils (provide fat), pollen (high protein)
pollinators are attracted by:
scent (sweet odor, pheromone mimics, dung/rotting meat odor) and floral pigments
pollination syndrome
floral traits associated with particular pollinators, can sometimes be used to predict pollinator from plant
bees
blue, yellow, or white flowers, good color vision and sense of smell, open during daytime, nectar: small volumes and concentrated
nectar feeding flies
light colored, open flowers
carrion flowers
prefers flowers that look and smell like rotting fish
butterflies
blue, purple, deep pink, orange red flowers, good color vision and sense of smell, nectar: often in narrow deep tubes
bats
light or dingy colored flowers, color blind, good sense of smell, active at night, open at night, plentiful nectar and pollen
moths
dull or white flowers, good sense of smell, active at night, less nectar in deep tubes
disperse seeds to:
reduce competition and inbreeding
seed dispersal mechanisms
water dispersed, wind dispersed, animal dispersed, seed hoarding, stick to fur
seed dispersal cues
color change and odor
convergent evolution
adaptation to similar environments can cause unrelated species to evolve similar traits
coevolution between animals and plants
adaptation to similar pollinators or plants can cause unrelated species to evolve similar traits
plants and non-animals coevolve
hosts and parasites can coevolve
ecology
the study of the distribution and abundance of organisms and the interactions that determine distribution and abundance
ecologists try to:
predict what will happen to an organism, population, community, or ecosystem and control the situation, minimize the effect of locust plagues by predicting when they are about to occur and taking appropriate action, predict which conservation policies are most likely to prevent species extinction and preserve biodiversity
scales in ecology
population, community, ecosystem, biome
carrying capacity
max number of organisms that an environment can support, population growth flattens when resources become limiting
possible fates of growing populations
exhaust resources: population crashes, nutrients added: carrying capacity fluctuates, richer medium: carrying capacity increases
predator prey cycles
prey population booms due to low predator frequencies, predation population grows due to abundant prey, prey population crashes due to predation, predator population crashes due to lack of resources, cyclical because resources recover
population growth rate
r (population growth rate) = b (birth rate) - d (death rate)
habitat
where an organism lives
ecological niche
a summary of an organism’s requirements in order to practice its way of life, includes ecological role of a species in a community
most common limiting factors in plants
temperature and moisture
mutualism
both organisms benefit, +/+
competition
both organisms cost, +/-
predation
+/-
parasitism
+/-
commensalism
positive effect on one species but no effect on the other, +/0
plant responses to competition
rapid growth: taller, deeper roots, tolerance of low resource availability, allopath: produce chemicals to affect competitors
Gause’s Law (competitive exclusion principle)
two species competing for the exact same resources cannot stably coexist
plant responses to herbivory
physical defenses: thorns and spines, chemical defenses: tannins and alkaloids, insect mutualists, rapid growth, meristem position
parasites
live in or on members of another species (hosts), absorb nutrients/energy from hosts
hemiparasites
green (photosynthetic) plants absorb water and nutrients from hosts
holoparasites
non-green plants absorb energy and nutrients from host
epiphytic plants
plants that grow on other plants, not parasitic
community ecology
the study of interacting populations of the species living within a particular area through time
succession
the process of change in the species structure of an ecological community over time
primary succession
on non-vegetated land (on bare rock), after glacial retreat, volcanic eruption
secondary succession
on previously vegetated land (soil present), abandoned farmland, after deforestation
energy
flows through ecosystems, entering as light and leaving as heat, nutrients cycle through ecosystems
food chain
description of the flow of energy through an ecosystem
trophic level
species grouped on the basis of what they eat, efficiency of energy transfer: about 10%
nitrogen cycle
most abundant element in the atmosphere, all life forms need nitrogen to make protein, DNA, and ATP
biodiversity
genetic diversity (less inbreeding, disease resistance), species diversity (measure that combines richness and evenness), ecosystem diversity
species richness
the number of species in a given area
species evenness
the proportions of species in an area
ecosystem services
soil formation and enrichment, water purification, oxygen production, carbon sequestration, temperature control, pollination (both crops and wild)
reasons to care about biodiversity
need genetic diversity to respond to future change, natural products (medicines, fertilizers, pesticides)
functional groups
set of species that fills a particular role, more more species present the more roles are filled
biomes
broad regions of similar ecosystems defined by climatic conditions
equator receives more solar energy than the poles due to:
angle of sun’s rays, distance light travels through atmosphere
climate changes: past ice ages
ancient air bubbles in ice (ice cores) help reconstruct past levels of carbon dioxide and therefore temperature, climate is constantly changing
centers of origin of major crops
farming arose independently in several centers around the world, approximately 8-10,000 years ago, occur in areas of high biodiversity
domestication
evolutionary process resulting in crop plants with useful traits from the wild form, driven by artificial selection for desirable traits, high fitness = agriculturally beneficial traits
domestication syndrome
set of traits that most domesticated animals share (good behavior, floppy ears, interesting coat colors, size, short/curly tails, tolerance of people), convergent evolution
useful crop traits
large seeds, high nutrient content, dry storage, pest or disease resistance, stress reliance, loss of: seed dispersal, self incompatibility, and seed dormancy
increased agricultural production worldwide as a result of:
plant breeding: improved crop yields, easy harvesting
development of inorganic fertilizers, fungicides, herbicides, and pesticides
monoculture
crops more susceptible to disease
genetic engineering
techniques to cut up and join together genetic material, especially DNA, from one species and introduce into an organism to change one or more its characteristics
genetically modified crop traits
herbicide resistance, insect pest resistance, virus resistance, nutrient enrichment, fungus resistance
herbicide resistance
reduces plowing, reduces soil erosion, reduces loss of beneficial microbes
insect pest resistance
Bt toxin affects only moths and beetles
virus resistance
only known resistance to papaya ringspot virus
improved nutrition
a low cost way to provide vitamin A supplements that prevent blindness and disease
environmental risks of GM crops
herbicide resistance, insect pest resistance, virus resistance, food safety, broader socio-economic issues
gene escape
geographic overlap, flowering time overlap, pollination, hybrid viability or fertility
sustainable agriculture
maintain mutualistic microbes and reduce soil erosion (decreasing plowing, use legumes as cover crops), use recycled fertilizers, intercropping (different crops in different rows), precision agriculture (GPS and drones) for pest control, crop and landscape diversity for better resilience to extremes in weather, pests, and market conditions
how can we be so far past stable carrying capacities?
exploitation of non-renewable resources (reliance on fossil fuels in agriculture, release of extra CO2 into the atmosphere), energy harnessed from the sun more than 100 million years ago
human impacts
extraction and burning of fossil fuels, deforestation, pollution (fertilizers, pesticides and herbicides, plastics, oil spills), fragmentation of native ecosystems, overexploitation of wildlife, invasive species
greenhouse gases
trap heat in Earth’s atmosphere, CO2, H2O vapor, methane (CH4)
consequences of climate change
hotter average temps, rising seas, more water in moist tropics and high latitudes, droughts in semi-arid low latitudes and mid-latitudes, extreme weather, species extinctions, changes in distribution of cereal crops, changes in disease distributions, direct effects of extreme weather
weed control
as carbon levels increase weed growth rate increases, stronger in weeds than in crops, herbicides become much less effective
invasive species
weedy species that heavily colonize or overwhelms a habitat, loss of biodiversity, increased carbon levels favor them in natural habitats, competitive advantage as atmospheric CO2 increases
causes of high extinction rates
overhunting, loss of keystone species, habitat destruction, habitat fragmentation
results in: inbreeding, genetic drift, possible extinction
