Exam 1 Flashcards
What type of animal is a “biological indicator”?
Amphibians
Why are amphibians biological indicators?
-Permeable skin; pollutants can pass through
-eggs have no protective shell
-they spend part of their life on land and part in water (exposure to many elements)
Ecology Definition
scientific study of how organisms affect, and are affected by, other organisms and their environment
Johnson Study on Pacific Tree Frogs
-Johnson suggested that a parasite causes deformities in the tree frogs
-Deformities in these frogs occurred only in ponds that also had an aquatic snail, an intermediate host of the parasite
-All frogs with deformed limbs had Ribeiroia cysts
Controlled Experiment
experimental groups are compared with a control group that lacks the factor being tested
What kind of experiment did Johnson et al. (tree frog parasites) run?
Controlled experiment
-There was a control group and 3 experimental groups
-As the number of parasites increases, fewer of the tadpoles survived and those who did had deformities
Kiesecker 2002
Hypotheses: pesticides decreases the ability of frogs to resist infection by parasites
-Six ponds, all with Ribeiroia, three with pesticides
-Wood frog tadpoles were placed in 6 cages in each pond; 3 had mesh size that allowed parasites to enter
Was there a cause found for a higher rate of Ribeiroia cyst formation in frogs that were raised in the presence of pesticides (Kiesecker 2002)?
They found that the tadpoles had fewer white blood cells (indicating a suppressed immune system) and a higher rate of Ribeiroia cysts
What are some environmental factors from fertilizers?
-Fertilizer runoff increases algal growth in ponds
-Snails that harbor Ribeiroia parasites eat algae
-Greater number of snails result in greater numbers of Ribeiroia parasites
What is the difference in Ecology and Environmental Science?
-Ecology refers to a scientific endeavor, NOT environmental activism
-Environmental Science incorporates concepts from the natural sciences (including ecology) and the social sciences and focuses on how people affect the environment and how to address environmental problems
What were the early ecological views?
There is a balance of nature in which natural systems are stable and tend to return to an original state after disturbance; each species plays a distinct role in that balance
Spatial Scales
-Small: soil microorganisms
-Large: atmospheric pollutants
Temporal Scales
-Short: leaf response to sunlight
-Long: species change over geologic time
Population
a group of individuals of a single species that live in a particular area and interact with one another
Community
an association of populations of different species living in the same area at the same time
Ecosystem
a community of organisms plus their physical environment
Landscapes
areas with substantial differences, typically including multiple ecosystems
Biosphere
all living organisms on earth plus the environments in which they live
Evolution
-change in genetic characteristics of a population over time
Descent with Modification
organisms gradually accumulate differences from their ancestors
Adaptation
a characteristic that improves the survival or reproduction
Natural Selection
individuals with certain adaptations tend to survive and reproduce at a higher rate than other individuals
Producers
use energy from an external source to produce their own food (autotrophs)
Net primary production
energy captured by producers minus amount lost as heat in cellular respiration
Consumers
get energy by eating other organisms or their remains
-heterotrophs
Nutrient Cycle
-Energy captured by producers is eventually lost from the ecosystem as metabolic heat
-Energy moves through ecosystems in one direction only-it can’t be recycled
-But nutrients are continuously recycled from the physical environment to organisms and back again
Methods to answer Ecological Questions
-observational studies in the field
-controlled experiments in the lab
-field experiments
-quantitative models
Example of Observational Field Study
Johnson et al. (1999); pacific tree frogs
-surveyed ponds to relate frog deformities with the presence of the parasite’s host snail
Example of Controlled Experiment
Johnson et. al (1999); tested their observations in the lab
Example of a Field Experiment
Kiesecker (2002); compared frogs from three ponds containing pesticides with frogs from three ponds that had no pesticides
Climate Change
A directional change in climate (such as warming and/or precipitation) that occurs over 30 years or longer
Replication
performing each treatment more than once; reduces possibility that results are due to a variable that was not measured or controlled in the study
How should you assign treatments in an experiment and why?
-assign treatments at random
-limits the effects of unmeasured variables
Stuart et. al (2004)
-analyzed studies on 435 amphibian species
-habitat loss was the primary cause for 183 species; overexploitation for 50 species
-the cause for the remaining 207 species was poorly understood
Skerrat et al. (2007)
-argued that some amphibian declines may be due to pathogens, such as chytrid fungus that causes a lethal skin disease and has spread rapidly in recent years
-There is some resistance in wild populations
-Climate change may also have an impact
Relyea (2003)
found that in 2/6 amphibian species, pesticides were up to 46 times more lethal if tadpoles sensed presence of a predator
Genes
made of DNA; specify (encode) protein structure; can have two or more forms called alleles
Genotype
genetic makeup of an individual; represented by letters
Evolution of a Gene
change in allele frequencies (proportions) in a population over time
How does descent with modification work?
Change through Natural Selection
-individuals with certain heritable traits survive and reproduce more successfully than other individuals
Does the population evolve in natural selection or do individuals evolve?
Population evolves through reproduction
Key Processes of Evolutionary Change
Mutation, Natural Selection, Genetic Drift, and Gene flow
Mutation
source of new alleles
Mechanisms that cause allele frequencies to change over time
natural selection, genetic drift, gene flow
Phenotype
Observable characteristics that are influenced by the genotype
Recombination
offspring have combinations of alleles that differ from their parents, producing different genotypes within a population
What provides the raw material for evolution?
Mutation
How often do mutations occur?
every 10,000-1,000,000 copies of a gene
Directional Selection
individuals at one phenotypic extreme are favored
Stabilizing Selection
individuals with an intermediate phenotype are favored
Disruptive Selection
individuals at both phenotypic extremes are favored
Genetic Drift
occurs when chance events determine which alleles are passed to the next generation
What is the effect of genetic drift drift on small populations?
- allele frequencies fluctuate at random; some may disappear, others may become fixed
- genetic variation of the population is reduced
- frequency of harmful alleles can increase if they have only mildly deleterious effects
- chance events may lead to allele fixation in one population and loss from another population
Loss of genetic variation…?
reduces the ability of the population to respond to changing environmental conditions
Increase of harmful alleles..?
can reduce survival and reproduction
What species was found to have fixation of harmful alleles due to loss of habitat?
Greater prairie chicken in Illinois
Gene Flow
alleles move between populations via movement of individuals or gametes
Effects of Gene Flow
-populations become more similar
-new alleles can be introduced into a population (acts similarly to mutation)
Gene Flow Example
Mosquitos with allele for insecticide resistance arose by mutation in Africa or Asia. They were transported by winds and humans to new locations. This increase the allele frequency in new populations
Adaptations
features of organisms that improve their ability to survive and reproduce
Natural Selection is not a _____ process.
random
Adaptive Evolutions
traits that confer advantages tend to increase in frequency over time
Example of Adaptive Evolution
-Carroll and Boyd (1992)
-feeding is most efficient if beak size matches fruit size in soapberry bugs
Clines
patterns of change in a characteristic over a geographic region
Phenotypic Plasticity
one genotype produces different phenotypes in different environments; may result in a continuous range of sizes or discrete types called morphs
What can occur if natural selection forces are strong enough to overcome gene flow?
adaptive evolution
________ can promote or limit adaptation.
Gene Flow
What are constraints on evolution?
lack of genetic variation, evolutionary history, ecological trade-offs
Lack of genetic information
if there is no beneficial allele, adaptive evolution at that gene cannot occur
Evolutionary History
natural selection on traits that already exist ; organisms have certain characteristics and lack others because of ancestry
Ecological tradeoffs
the ability to perform one function may reduce ability to perform another function
What is adaptive evolution driven by?
ecological interaction-organisms interacting with one another and with their environment
Speciation
process by which one species splits into two or more species
Why does speciation occur?
when a barrier prevents gene flow between 2 or more populations of a species (barriers can be geographic or ecological)
What is the key step of reproductive barriers?
reproductive barriers
What is the by-product of natural selection?
reproductive barriers
Evolutionary tree
branching diagram that represents the evolutionary history of a group
How old are the oldest multicellular fossils?
2.1 billion years old (red algae)
How many mass extinction events have occurred?
5
What followed each mass extinction event?
adaptive radiation: increased diversity of the surviving groups
Coevolution
reciprocal evolutionary change in interacting species
What are the characteristics of life history?
-age and size at sexual maturity
-amount and timing of reproduction
–survival and mortality rates
Life History strategy of a species
the overall pattern in average timing and nature of life history events
What is life history shaped by?
how the organism allocates energy and resources between growth, reproduction, and survival
What does natural selection favor in individuals?
ones whose life history traits result in their having a better chance of surviving and reproducing (fitness)
Allocation
the relative amounts of energy or resources that an organism devotes to different functions
Asexual Reproduction
simple cell division (binary fission): all prokaryotes and many protists
Isogamy
gametes are equal in size
Anisogamy
most multicellular organisms produce gametes of different sizes; the egg is usually much larger and contains nutritional material
Disadvantages to Sexual Reproduction
-an individual transmits only half of its genome to the next generation
-population growth rate is only half that of the asexually reproducing species
-recombination and chromosome assortment during meiosis can break up favorable gene combinations
Benefits of Sexual Reproduction
recombination promotes genetic variation and better ability of populations to respond to environmental challenges
Complex Life Cycles
at least 2 stages with different body forms that live in different habitats and eat different foods
Metamorphosis
abrupt transition between larval and juvenile stages
Alternation of Generations
a multicellular diploid sporophyte alternates with a multicellular haploid gametophyte
Direct Developmental
the fertilized egg develops into a juvenile without passing through a larval stage
What is the trade-off between size and number of offspring?
the larger the investment in each individual offspring, the fewer offspring can be produced
Lack Clutch Size
maximum number of offspring a parent can successfully raise to maturity
Lack Clutch Size Experiment
-David lack (1947)
noticed bird’s clutch size increases with latitude; longer daylight hours may allow parents more time to forage and feed more offspring
Nager et al 2000
experimental manipulation of clutch size in lesser black-backed gulls showed that in larger clutches, offspring have less chance of survival
What are resources invested in when there is no parental care?
propagules (eggs, spores, or seeds)
-size of the propagule is a trade-off with the number produced
-in plants, seed size is negatively correlated with number of seeds produced
Allocating resources to reproduction decreases….
an individual’s growth rate, survival rate, or potential for future reproduction
By allocating resources to reproduction instead of growth, an individual….
will reproduce at a smaller size
Parental Investment
-provisioning eggs or embryos, yolk and protective coverings for eggs, nutrient-rich endosperm in plant seeds
-Parental Care: invest time and energy to feed and protect offspring
Dispersal
movement of organisms or propagules from their birthplace
Dispersal ability has evolutionary significance (Hansen 1987)
fossil marine snail species with swimming larvae had larger geographic ranges and tended to go extinct less often than species that developed directly into crawling juveniles
Dormancy
state of suspended growth and development in which an organism can survive unfavorable conditions
Ecological niche
habitat and resource requirements that an organism needs to grow, survive, and reproduce
Niche Shift
size or age specific changes in an organisms ecological function or habitat
What is the optimal condition for an organism to undergo a niche shift?
when they reach a size at which conditions are more favorable in the adult habitat than in the larval habitat
Dahlgren and Eggleston 2000 study
found that smaller juveniles are very vulnerable to predators in the rocky habitats, but larger ones were not ; niche shift was timed to maximize growth and survival
If the larval habitat is favorable, metamorphosis may be….
delayed or eliminated
How many times do Semelparous species reproduce?
once
How many times do iteroparous species reproduce?
multiple times
r-Selection
selection for high population growth rates; an advantage in newly disturbed habitats and uncrowded conditions
K-selection
selection for lower growth rates in populations that are at or near K, the carrying capacity
-advantage in crowded conditions, efficient reproduction is favored
r-Selected species
-“Live fast, die young”
-short life spans, rapid development, early maturation, low parental investment, high reproduction rates
K-selected species
-“Slow and steady”
-long lived, develop slowly, late maturation, invest heavily in each offspring, low reproduction rates
Barby 2002 Study
compared three butterfly species. The one in drier, less predictable habitats had more r-selected characteristics. The ones found in more predictable wet forest habitats had k-selected characteristics
Stress
any abiotic factor that limits growth
Disturbance
any process that destroys plant biomass
Low stress/low disturbance habitats
competitive plants with superior ability to acquire light, minerals, water, and space have an advantage
low stress/ high disturbance habitats
plants with short life span and rapid growth rates, such as ruderals are favored. They can exploit habitats after disturbance has removed competitors
High stress/low disturbance habitats
stress tolerant plants may have slow growth rates, evergreen foliage, slow rates of water and nutrient use, low palatability to herbivores, and ability to respond to temporarily favorable environments
