topic 1 Flashcards
define ecology
ecology is the study of interactions between organisms and their environment that determine their distribution and abundance
ecology is inter deciplinary. describe its hierarchical organization
each level has its own set of properties
largest to smallest: ecosphere, biome, landscape, ecosystem, community, pop, organism etc
define population
• A group of interacting individuals (possibly interbeeding) individuals of the same species that occupy a given area (at a given time)
○ HAVE TO BE INTERACTING!!
define pop ecology
The study of the abundance, distribution, and other population characteristics of organisms (the things we measure and study)
how is abundance measured
• Abundance ( usually N or n)
○ Population size: # of individuals
○ Population density: # of individuals per unit area (or volume)
Biomass density: biomass per unit area or volume (tonnes fish/ m^3)
why is abundance important
This is really important as it determines whether a species is common or rare, safe harvest levels. It also influences how populations evolve
what is spatial distribution? types?
arrangement in space
○
○ Has to do with the probability of finding an individual in any given spot
uniform, random, clumpex
what are vital rates? what does it influence? how can it vary?
Vital rates: birth rate (fecundity), death rate (mortality)
influences abundance
varies with age = age structure important
describe age structure
• Age structure
○ Number of individuals in different age categories
○ Often separated by sex
Shape of age structure graph can tell us a lot
describe stage structure
○ Population broken down by size, developmental stage, etc.
○ Ex. Balsam fir trees based on trunk size or insect that goes through stages
describe sex ratio
○ Influences growth rate of pop.
Not all populations have straightforward sex ratios (asexual hermaphroditic, etc)
describe geographic range
Where a species is found, larger range than spatial
define evolution. how does it occur? what does it require?
• Change in the properties of populations over the course of generation
• Occurs via natural selection (adaptive evolution), but also by other processes
• May be slight or substantial
• Individual organisms do not evolve - pop.s do
Requires variation within a population
how can genetic variation occur?
• Can occur between and within populations
• Variation in genotypes (genetic makeup of organism)
Variation in phenotype (genes and environment); physical, physiological, or behavioural traits
how is pop level variation contained
• Population level genetic variation contained within gene pool
what is the gene pool? what does it measure?
• Sum of genetic info (alleles) across all individuals in a population (total genetic variation)
• Measures of total genetic variation: allele, phenotype, or genotype frequency
Basic level at which evolution occurs, e.g., the gene poor changing over time
3 ways genetic variation is generated
- Mutation
- Sexual recombination
- Immigration / gene flow
- Mutation
describe + define mutation
• Any heritable alteration of genetic material
• Change in nucleotide sequence
○ Often random process - cell division copying errors
○ Radiation, viruses, UV rays, etc
• Often a change from one allelic form to another
• May be harmful, neutral, or beneficial
Effect depends on the environment
describe sexual recomb
- 1/2 alleles from each parent
- Alleles dealt at random
- Changes from generation to generation in large populations
describe immigration/ gene flow
• Movement of individuals into a population
• leads to gene flow
Only contributes to genetic variation in the population if immigrants reproduce
describe natural selection - who came up with it
• Charles darwin and alfred wallace 1858 - came up with the theory, both independently proposed the theory
* Organisms well adapted to their environment transmit heritable genetic characteristics to subsequent generations * Favors traits (adaptations) that result in an organism leaving more descendants (higher fitness) * Adaptive evolution maximizes fitness of individuals overtime
describe fitness
• Proportionate genetic contribution that an individual makes to future generations
• Depends on individual survival and reproduction (and that of the descendants)
• Different strategies to optimize fitness
Relative term: same species
requirements for natural selection
- Variation in reproductive success
- Variation in traits / phenotype
- Correlation between traits and reproductive success
- Heritability of those traits
If any of these are violated no natural selection will occur on that trait
ex. pepper moth
3 modes of selection? know the graphs
stabilizing, directional, diversifying
describe stabilizing selection
eliminates extreme variants from pop - trend towards reduced phenotypic variation and maintains status quo
describe directional selection
shifts makeup of the pop by favoring variants of one extreme.
diversifying selection describe
favors variants of opposite extremes over intermediate individuals
what does the speed of selection depend on
• Signficant variation, depends on:
○ Strength of selection
○ Population size - large populations typically have higher genetic variation = more likely that natural selection will act on it
limitations to adaptation
• Adaptations are limited by: ○ Mutations and gene flow ○ Constantly changing environments ○ Historical evolutionary constraints ○ Each trait represents a trade off with costs and benefits
what is net result of selection
Net result of selection over time: organisms become better adapted to their environment
adaptation trade off - describe clutch size in birds - what is favored vs reality?
• Varies in different birds
• Optimal clutch size
• Natural selection should favor birds that leave the most descendants (not necessarily those who lay the most eggs)
• Many birds lay fewer th • Ovulation stops before max - trade offs - putting all their energy into making eggs - cannot feed and protect them all
• No organism has unlimited energy or resources
• All activities have benefits and costs
an their physiological max
what are trade offs?
reproduction mazimized within constraints of other energy requirements (ex. feeding young, protect from enemies, defend territory)
what is lack’s hypothesis on clutch size
• Clutch size in birds that feed their young in the nest) was adapted by natural selection to correspond to the greatest number of young for which the parents can provide adequate food
If the number of offspring is too high, the offspring quality will decline (inadequate food) - reduces overall fitness
look at graph for cost-benefit model. which clutch size is optimal for max profit/fitness
ok. clutch size w/ max. difference between benefits and cost is optimal for individual profit max
how was lack’s hypothesis tested by pettifor in 1993?
• Blue tit - 11 eggs in nature
• Prediction: fitness maximized at 11 eggs/clutch due to reductions in offspring quality at higher clutch sizes
• Pettifor artificially manipulated broods
○ Added or subtracted chicks
○ Counted number of offspring surviving
Support for lack’s hypothesis
deviation from lack’s hypothesis?
additional fitness trade offs beside offspring quality: adult survival + future reproduction
many species have a normal clutch smaller than most preductive based on # of offspring surviving
benefits and costs of increased clutch
Increased clutch size
Benefits: more descendants (+ fitness)
Costs:
— Energy to make eggs (can affect future
survival/reproduction)
— Energy to feed additional offspring ( can affect offspring
quality (Lack’s hypothesis) & future survival/reproduction)
other processes that lead to variation in gene pool?
- Mutation and gene flow
- Genetic drift - chance variation in allele or genotype frequencies from generation to generation (pronounced in small populations)
describe genetic differentiation. how does it occur? results in?
• Genetic variation among subpopulations of the same species
○ widely distributed species experience a range of environmental conditions leading to genetic differentiation
○ Greater distance = greater differentiation
Results in variation in particular characteristics that represent different adaptations
what can genetic differentiation occur as?
- Geographic variation and resulting genetic differentiation within a subpopulations of a species can occur as:
- Clines
- Ecotypes
- Geographic isolates
describe clines
• Gradual change over a geographic region
• Continuous variation in a trait or genotypic frequency
• Associated with particular environmental gradients - temp, precip
• Usually gene flow between populations along the gradient
•
ex. different in height of yarrow pops - common garden
• Common garden environment used to test if its genetics or environment - is the trait retained in a common environment
Often due to both factors
look into cline more
ok
describe ecotypes
• Marked discontinuity in traits
• Reflect abrupt changes in environment
ex. morphs of snail shells - H morph in crevices on cliff face = smaller, thin shell
M morph on boulders on shore = larger, thick shell
describe geographic isolation
• Populations isolated due to geographical features
• Low gene flow between populations (little immigration and emigration)
• Degree of isolate depends on geography - rarely complete
May lead to specialization
ex. 2 spotted owl sub species showing genetic and morphological differences - living in diff locations
