Unit 4 Flashcards
What is taxonomy?
the branch of science concerned with
classification, especially of organisms; systematics.
What is phylogenetics?
the study of evolutionary relationships among species
What is a clade?
A group of related organisms on a phylogeny
What do shared characters suggest?
A common ancestor with that character
What can characters be based on?
morphological traits (e.g. seeds, backbones), DNA, protein sequences
How do scientists infer evolutionary relationships from character information?
Occam’s Razor: the simplest solution is probably the best one
*aka the concept of parsimony
Phylogenetic trees can be based on:
DNA, protein sequences, morphology
What is a monophyletic group?
Group in which all species share the
same common ancestor, and all of the descendants of that ancestor are in the group
What is a paraphyletic group?
Group in which all species share the
same common ancestor, but do not include all species descended from that common ancestor
In taxonomy and phylogenetics, it is ideal that…
All groups at all levels
should be clades (monophyletic), and this hierarchy should reflect evolutionary relationships
Phylograms are drawn to what scale?
A genetic distance scale.
Why use phylogenies?
Asexual reproduction is…
-creating an exact replication of yourself somewhere else
- Mitotic (mitosis only, never does meiois)
-Simple life cycles where ploidy stays the same, possibly with asexual reproductive structures
- Eukaryotic organisms: plants, fungi and some animals (mitosis only, no meiosis, no fertilization)
Sexual reproduction is…
- creating offspring that is not identical
-Meiotic - Complex life cycles with haploid (N) and diploid (2N) stages and specialized reproductive cells
- Sexual life cycle: gametic e.g. animals (mitosis: 2N), sporic e.g. plants (mitosis: N & 2N)
-reducing your genes, makes haploid cell that then combines with someone else’s cell to make a new diploid cell
- if a plant has a flower, it undergoes sexual reproduction
What are the female parts of a flower called?
A pistil
What are the male parts of a flower called?
A stamen
What are flowers with both stamens and pistils called?
hermaphroditic
Monoecious plants have…
Both a stamen and pistil
Dioecious plants have…
A stamen and pistil on separate plants
Pollination is…
Transfer of pollen from anther to stigma
Pollination can occur…
-within a flower
-between flowers on the same plant
-between flowers on different plants
Mechanisms to avoid inbreeding include…
- self incompatibility
- Timing of pollen shedding or stigma receptivity
- Flower shape
- Dioecy
Explain self incompatibility.
Pollen can be blocked:
- at the stigma surface
- during growth to ovule
*Plants can recognize their own pollen based on genetic similarity
Most flowering plants are…
- animal pollinated
- attract multiple pollinators
- generalists
What is a generalist?
Pollinators that visit multiple plant species.
What is a specialist?
Pollinators that visit a specific plant species.
What kinds of rewards do pollinators seek?
- Nectar (sugar/amino acids)
- Oils (provide fat)
- Pollen (high protein)
Pollinators are attracted by…
*Scent
- Sweet odor
- Pheromone mimics
- Dung/rotting meat odor
*Floral pigments
What does UV coloration encourage?
directs insects to nectar (and pollen)
What do landing pads encourage?
walk around, pollinate
What does restricted access prevent?
nectar robbing, ensures pollination
Define pollination syndrome.
Floral traits associated with particular pollinators. Can sometimes be used to predict pollinator from plant.
Pollination syndrome for bees and bee pollinated flowers:
-Good color vision (into UV); red blind
- Flowers typically: blue, yellow or white
- May have visible nectar guides (spots)
- Often irregular (bilateral)
- Good sense of smell
- Often fragrant
- Open during daytime
- Nectar: small volumes, concentrated
Birds and bird-pollinated flowers:
- Good color vision; especially red
- Flowers often red
- Poor sense of smell
- Little or no scent
- Open during daytime
- Nectar: large volumes, dilute
Nectar-feeding flies:
- Prefer light colored, open flowers
Carrion Flies:
- Prefer flowers that look and smell
like rotting flesh
Butterflies:
- Good color vision
- Flowers: blue, purple, deep pink,
orange red - Good sense of smell
- Often fragrant
-** Feed with tubular proboscis** - Nectar: often in narrow deep tubes
- Require landing platform
Bats:
- Color blind
- Flowers: light or dingy colors
- Good sense of smell
- Strong odors
- Active at night
- Open at night
- Plentiful nectar and pollen
- Open shape, easy access
Moths:
- Dull or white flowers
- Good sense of smell
- Active at night
- Long proboscis, deep tubes
- Less nectar, landing platform
Why disperse seeds?
- To reduce competition
- To reduce inbreeding
Some seed dispersal methods include…
- Water-dispersed (e.g. coconuts)
- Wind dispersed (non-targeted)
- Animal dispersed
Animal dispersal is beneficial because it is…
- predictable and targeted
Mechanisms of animal dispersal include…
- Feed on fruits, seeds pass
- Seed hoarding (e.g. squirrels)
- Stick to fur (or socks!)
Seed dispersal cues include…
- Color change
- Odor
*These methods encourage the dispersal of mature seeds
Define Ecology
The study of the distribution and abundance of organisms and the interactions that determine distribution and abundance
Define population
All the individuals of a given species
present in an area
Define community
All the populations present in a
given area
Define ecosystem
the community together with the
abiotic environment in which it is set
Define biome
broad regions of similar ecosystems
defined by climatic conditions
Carrying capacity:
- Max # of organisms: that an environment can support
- Population growth flattens: when resources become limiting
What happens when you exhaust resources?
population crashes
What happens when nutrients are added?
carrying capacity fluctuates
What happens when there’s a richer medium?
carrying capacity increases
In a closed system…
there are fixed limits
Formula for population growth…
r (population growth rate) = b (population birth rate) - d (population death rate)
If the population value is r > 0
Positive, the population is growing
If the population value is r = 0
No change
If the population value r < 0
Negative, the population is decreasing
Define habitat…
where an organism lives
Define 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 (interaction with other species))
The most common limiting factor in plants is…
temperature and moisture
Define mutualism
both organisms benefit (eg plants and pollinators)
Define predation/parasitism
-one organism benefits, the other is hurt
-eg.) Herbivory: Consumption of
plants by animals
Define commensalism
positive effect on one species, but …
no effect on the other species
Define competition
Both organisms cost
-Results in a reduction of reproduction or survival
Examples of mutualism
-Pollination
-Seed dispersal
-Herbivory
-Defense
Describe plant and microbe mutualism
-Fungi and bacteria in soil provide nutrients to plants
-Plants need nitrogen, phosphorus:
Proteins, DNA, ATP
-example: Mycorrhizae (root fungi)
- = fungi that live on or in the
roots of plants
- carbon source for fungus is:
sugars from plant
- expand the root system:
provide nutrients to plant
Plant responses to competition…
-Rapid growth: taller, deeper roots, etc. (= resource pre-emption)
-Tolerance of: low resource availability
-Allelopathy: produce chemicals à affect competitors
-Rhododendron understory:
lack of herbaceous plants
-Adaptations to prevent:
overlapping needs
Describe Gauze’s Law (competitive exclusion principle)
Two species competing for the exact same resources cannot stably coexist
What are some plant responses to herbivory
-Physical defenses: thorns, spines, etc.
-Chemical defenses: e.g., tannins, alkaloids
-Also: insect mutualists, rapid growth, meristem position
What are some characteristics of plants as predators?
- Plant carnivory has evolved many times independently
- Traps are usually modified leaves
- Examples: passive pitcher plants, active fly traps
parasitism in plants…
-Parasites: live in or on members of another species (hosts), absorb nutrients/energy from hosts
- Parasites of plants (e.g. viruses, fungi)
- Plant as parasites
Define hemiparasites
green (photosynthetic) plants… absorb water and nutrient from hosts
Define holoparasites
non-green plants…absorb energy and nutrients from host.
Define epiphytic plants…
plants that grow… on other plants
Epiphytic plants get moisture and nutrients from…
air, rain, debris
Are epiphytic plants parasitic?
No
Define community ecology…
The study of interacting populations of the species living within a particular area through time
Define succession…
The process of change in the species structure of an ecological community over time.
Define primary succession…
on non-vegetated land (on bare
rock) e.g. after glacial retreat, volcanic eruption
Define secondary succession…
on previously vegetated land (soil
present) e.g. abandoned farmland, after deforestation
Describe the process of primary succession when glaciers retreat.
1.) Retreating glaciers expose bare rock
2.) Pioneer species like lichen
and moss create the first soil
3.) Pioneer plants
*Climax community: stable,
(self perpetuating) stage
Describe the process of secondary succession in the tropics.
1.) Pioneer species colonize first
Good dispersers, rapid growth
*Climax community: stable,
(self perpetuating) stage
*Shade tolerant, slow growing
Define food chain…
description of the flow of energy through an ecosystem
Define trophic level…
species grouped on the basis of what they eat
Larger numbers of organisms are usually at ________ trophic levels.
lower
There is more _______ at lower trophic levels.
biomass
*rodents need much more than their weight in acorns for sustenance. Owls need more than their weight in rodents
What is the efficiency of energy transfer between trophic levels?
~10%
A food web is…
a more complex and complete
representation of: trophic (feeding) structure
Define a keystone species…
Species that have far-reaching effects on ecosystems
Why do trophic cascades happen?
A keystone species is lost.
How does energy cycle through ecosystems
Energy enters as light and leaves as heat
Describe the nitrogen cycle…
- most abundant element in atmosphere
- not in a form that plants or animals can use
Human effects on the nitrogen cycle include…
- Fertilizers
- Nitrogen pollution
How does matter cycle through ecosystems?
through biotic and abiotic pools
What predicts how hot past global temperatures were?
Carbon dioxide (CO2) levels
Define species richness…
the number of species in a given area
Define species evenness…
the proportions of species in an area
Define species diversity…
measure that combines richness and evenness
Ecosystem services require high levels of biodiversity for sustaining stable communities. Some of these services include…
- 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)
Species diversity is needed for…
ecosystem resilience
Functional groups are…
- Set of species that fills a particular role e.g. photosynthesis or nitrogen fixation
- The more species present, the more roles are filled
What is a biome?
broad regions of similar ecosystems defined by climatic conditions. Ecosystems in the same biome may contain different communities of species.
Climate determines locations of _____.
biomes
Why does the equator receive more solar energy?
- angle of sun’s rays
- distance light travels through
atmosphere
What causes seasons?
the tilt of the earths axis
*the sun’s solar radiation strikes the Earth at different angles depending on latitude and season
______ affect levels of precipitation.
Air currents
Plant and animal diversity tends to be _______ at low latitudes (near the equator)
higher
Diversity also tends to be higher with more __________.
precipitation
Where did farming arise?
Farming arose independently in several centers around the world. There are at least 10 different centers of origin for today’s most economically important crops.
Farming began around _______ years ago.
10,000
_____________ is an evolutionary process resulting in crop plants with useful traits that differ from the wild form
Domestication
Domestication is driven by ______ _______ for desirable traits
artificial selection
*High fitness = agriculturally beneficial traits
Define domestication syndrome…
Set of traits that most domesticated animals share
eg.) Most domesticated animals: a reduced fear of people, not biting, floppy ears, interesting coat colors, size
Some useful crop traits include…
- Large seeds, high nutrient content, dry storage
- Loss of: seed dispersal, self incompatibility, seed dormancy
- Pest or disease resistance
- Stress resistance e.g. salt or drought tolerance
__________ plants have larger cells and tend to be larger plants.
Polyploid
The _______ ____________ (1930’s to 1960’s) was an Increased agricultural production worldwide.
Green Revolution
The Green Revolution was a result of…
- Plant breeding: improved crop yields, easy harvesting
- Development of inorganic fertilizers, fungicides, herbicides and pesticide
One example of monoculture and disease in the US is…
In the 1970s, 90% of the corn crop in the USA was hybrid corn. Southern corn leaf blight destroyed 15% of US corn.
Increased agricultural production worldwide from the 1970’s to now is a result of…
- Plant breeding: improved crop yields e.g. disease
resistant dwarf wheat and rice in tropical countries - Development of inorganic fertilizers, fungicides and
pesticide
Now, crops are crossed with wild relatives to…
Increase disease resistance & yields in different climates
Not all traits can be easily achieved via breeding- Why?
There may not be heritable (genetic) variation for a trait
Some examples of genetically modified crop traits include…
- Herbicide resistance: RoundUp Ready
- Insect pest resistance: Bt corn
- Virus resistance: Papaya
- Nutrient enrichment: Golden Rice
- Fungus resistance: American chestnut
Most common early types of genetically modified crops are…
- HT = herbicide tolerant
- Bt = insect resistant
What does herbicide resistance help with?
reduces ploughing, reduces soil erosion, reduces loss of beneficial microbes
What does insect pest resistance help with?
Bt toxin affects only moths and beetles. No sprays: affects only insects that eat the crop
Environmental risks of herbicide resistance and insect pest resistance include…
Herbicide resistance:
- Spread of transgene: natural crosses spread herbicide resistance to wild relatives or neighbor’s crops
- Herbicide resistance evolves in weeds
Insect pest (Bt) resistance:
- Effects on other insects
- Spread of transgene: natural crosses spread pest
resistance to weeds or neighbor’s crops
Other risks:
Food safety (e.g. new allergens) (no evidence),
Broader socio-economic issues: e.g. food price & availability
Define transgene…
gene from the DNA of one organism & introduced
into the DNA of another organism by artificial techniques
What is the problem with transgenes.
- GM crops may hybridize with wild relatives, leading to the escape of transgenes into the wild
- Many crops flower at the same time as their wild relatives
- Transgene escape is almost inevitable
For genes to escape you need four things…
- Geographic overlap
- Flowering time overlap
- Pollination
- Hybrid viability or fertility
What are some characteristics of sustainable agriculture?
Utilize farm landscapes that resemble natural ecosystems:
- Maintain mutualistic microbes and reduce soil erosion:
decrease ploughing, use legumes as cover crops
- Use recycled fertilizers (compost, manure)
- ‘Intercropping’ (different crops in different rows)
- Soy or alfalfa to provide nitrogen for corn or cotton
- Onions mask scent of carrots, keep pests away
- Crop and landscape diversity for better resilience to
extremes in weather, pests and market conditions
– Precision agriculture (e.g. GPS data and drones) for
pest control, yield increase
