Unit 2 (2/5-xxx)
Environmental Bio 🎉
___(I. Mitchell)
Population ecology: how populations interact with their environment
Includes birth, death rates, and immigration and emigration
How do population sizes change through timeÂ
Population: # of organisms of the same species that live in a particular area at the same time, with the ability to interbreed
How populations grow
3 common patterns of growth (show their potential if there are no limitations (their unlimited ability)
Arithmetic
Growth isn't constant
Not realistic long-term
The growth increases constantly over time; the same # individuals are added at each generation.
Exponential (J-shaped growth)
Growth accelerates with each generation
Not realistic long-term
Growth whose rate becomes ever more rapid in proportion to the growing total number or size often when resources are available in a new environmentÂ
Both are unrealistic because of the presence of diseases, predators, etc.. ( THEY DO NOT FACTOR IN ENVIRONMENTAL CHANGE AND LIMITATIONS)
Population growth rate
(percentage of population that is new divided by time)
% change per year
Doubling time: the length of time required for the population to double in size
Quick estimate=(70/population growth rate)
About 10% accurate
Steps to double time:Â
take 70 âž—the percentageÂ
Add that to the current year.
How to calculate the net number (how much does it grow after you take out the losses)
(net number of new individuals)
growth rate= (Birth + immigration) - (Death + Emigration)
Birth
Reproduction
Death
Mortality
Immigration
# enteringÂ
Emigration
# leavingÂ
Exponential Growth Formula: (take from slideshows)Â
Population Growth rates vary by species
The smaller the organism, m the faster they grow, and the smaller their growth rate
Growth with limits (takes the “s” shaped curve)
Populations cannot grow forever
There are limits to growth
Carrying capacity: the maximum number of organisms the environment can support
Competition reduces the reproduction rate
Range of tolerance also affects reproduction rates
Environmental resistance: Factors affecting population growth
As resources deplete, birth rates decrease, and deaths increase Â
A more realistic pattern of growth
Logistic growth: occurs when resources are limited,d thereby setting a maximum number an environment can supportÂ
Fast when the population is small, slower as the population is large
Range of tolerance: range between minimum and maximum values for survival
Temp
Space
Chemical
(often Abiotic)
Habit and Niche
The range of tolerance for various factors determines…:
Habitat: the complex environment organism depends on for survival
The location you can describe
Temperature, humidity, living elements like food and nutrients
Ecological Niche: the role an organism fills and performs in the ecosystem
What it does
Various activities the organism performs and how it does it
The complex includes all interactions
Biotic and abiotic in the ecosystem
Trick:
Species: its name
Habitat: its address
Niche: its career or how it makes a livingÂ
Survivorship: the probability of an organism dying during a particular interval
Species survival varies widelyÂ
Type 1: most die old
Type 2: Young and old people die equally
Type3: most die young
Can organize exceed their carrying capacity
What does it mean
Organisms can temporarily exceed their carrying capacity because, many times,s they produce more offspring than the environment can support
Who lives and who dies is based on who can get the most resourcesÂ
EVOLUTION:
Inherited changes in a population over time (individuals don't evolve; the population does)
Genetic change in a population
Across generations (the offspring, reproduction)
Descent with modification (Charles Darwin)
Is the major unifying concept in biology
Population evolve in response to ecological pressures; an understanding of evolution and ecology helps understand why organisms are the way they areÂ
Ecological pressure
Individuals do not evolve
There are different ways population evolve
Adaptive evolution: species become better suited to their environment over time (natural selection)
The only adaptive evolution
Non-adaptive evolution: species do not become better suited to their environment
Artificial selection
Genetic drift
Other mechanismÂ
All evolution starts with mutation, the ultimate source of natural variations.
Mutations: random changes in DNA
Artificial selection: the process by which humans use animal and plant breeding to selectively develop particular traits by choosing which animal or plant makes and females will sexually reproduce and have offspring together
Form of differential reproduction: when some individuals in a population have more offspring than others due to their traits
Solely based on which traits humans deem desirableÂ
These traits make them less suited to live on their own-adaptive evolution
Non-random evolution (people influence)
Natural selection: Certain members of a population may be better suited to their environment; therefore, they are more likely to survive and produce offspring that inherit the beneficial traits
Nature must also be able to influence differential reproductionÂ
It is also of differential reproduction
Fitness Biological : biological in terms of evolution
The ability of organisms to produce viable offspring
Measured inability to have grand offspring
Differential reproduction is influenced by fitness
EX: Mules cannot produce offspring, and so has no Fitness
Fitness is influenced by the ability to survive and reproduce in the environment
Adaptations: Inherited structures, functions, and behavior, that increase the ability to survive and reproduce in the environment (traits)
Most Fit leave more offspring; their adaptation becomes more common
Less fit have fewer offspring; their adaptation becomes less common
The population changes over timeÂ
Natural selection steps:
1. There is variation in the trait within the population
2. The trait is determined by genetics and hence heritable
DNA encodes for that trait
3. Individuals with certain variants of the trait have higher fitness
4. There is competition for survival and reproduction between individuals within a population
Disclaimer: Survival and reproduction of the fittestÂ
Those that are better able to compete within this struggle for existence = have higher survival and pass on to offspring rates
Adaptive evolution
Non-random evolution (environmental influenceÂ
EX: Darwin’s fished
Galapagos Island
14 species occupy a variety of different niches
Adaptive radiation: when several species evolve from a single ancestral species to occupy new niches
Evolution is not always slow and gradualÂ
The trait is only as beneficial as its current environment
Three types of natural selection
Directional: one end of the range of variation favored
Stabilizing: middle range of variation favored
Disruptive: both extreme ends of the variation are favored over the average traits.Â
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Genetic drift is completely random.
A change in the frequency of an inherited trait that is caused by a chance eventÂ
Non-adaptive evolution (not caused by fitness)
Do not become more suited for their environment
Random evolution (not caused by adaptive traits)
Founder effect: type of genetic driftÂ
A change in the frequency of an inherited trait that is caused by a small subset of the population
EVOLUTION OF SPECIES
Population may change or split into different species since they become isolated from each other and follow different evolutionary pathways.Â
Evolution is not linear.
Linear progression andreplacementss falseÂ
Involved diversification
Branch points
Productive isolation: members of one species do not interbreed with members of other species ( breeding barriers)
Isolation keeps groups separate while they may be evolving into separate species
Isolation keeps groups separated after they have evolved into separate speciesÂ
A hybrid between two species are often sterile, like the mule
Types of reproductive isolation
Geographic isolatioSeparateded by space
Keeping to their known environments
Temporal isolation
TimeÂ
Matting at different times
Behavioral isolation
Courtships
singing, dancing, body postureÂ
Every species has a titsown courtship
Only recognize the song of the same species
Structural isolation
Different structures for different species
Human effects on evolution and extinction
Humans affect evolution in waysÂ
Artificial selection
Humans cause a lot of extinction
The flipside of evolution and speciation is extinction
Dying out or extermination of a species
Note: wasnt feeling good on the 14th and 17th, notes are incomplete
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Mass extinction:Â
In a short period, planet-wide
Background Extinction:
The average rate of extinction between mass extinction events; is always occurring.Â
Species that cannot evolve and adapt to a changinenvironmentnt are designed to go extinct.Â
We are possibly in a 6th major extinction event, which humans may causeÂ
Pre- agreiculutral Period
Begin 100,000 years
Demographic Transition Model
Pretransiuiona
Birth and death =high rate
Limited resources,
Deaseae spread fast
2/17Â
The more developed nations have lower birthrates
Lower birth rates correlate to higher GDP
Age structure
Determined by survuvirship and age-specific bith rate
Age structure pyramid
Graphically display age structure
Shape indicates rate of population growth
Population of 8.1 billion people on the planetÂ
9 million in 15 years
Rapid population growth in the last 250
Source of many of our environmental issues
Rate of consumption
Everyone doesn't use the same amount of resocers
Everyone doesn't has the same access to resources
Varies by country and their national economy tremendously
Human population growth is exponential
Ecological footprint: area of land needed to supply resources consumed by peopleÂ
Includes: cropland, grazing, forests, fisheries, carbon footprint, but-up land, water, and waste disposal
Suitability vs caring capacity
Caring capacity is the size ofthe population environment that can supportÂ
As population approach
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Human resources use
Biocapacity: area and quality of land available to supply resources
Population whose ecological footprint exceeds their capacity must have good imported
Ecological debtors
Populations whose biocapacity exceeds their ecological footprint may export goods: ecological creditors
Wealthy nations rely on the resources of the creditorsÂ
Community Ecology:
Definition: examines how organisms in a community interact with each other and their environment
The study of the organization and functioning…
Community: a group or association of population of two or more different species occupying the same geographical area and in a particle timeÂ
In a community, multiple species coexist and interact (biotic interactions)
Six categories of how they interact with each other
Competition (Biological)
2 or more groups in question must use the same resource
The resource must be in short supply
The fitness (biological fitness)Â of each group is reduced when they occur together
No matter what both parties lose fitnessbecuse when they spend time competing, it's not spent on reproducing resting, or getting food ( competing is a limiting factor when it comes to fitness)
This causes more energy and time to be spent gaining fewer resources than they normally would (this is a disadvantage to all involved)
Any 2 species (even plants) can competeÂ
ALL OF THE TYPES OF COMPETITION CAN BE STACKED ( A SITUATION CAN HAVE MORE THAN ONE TYPE)
Exploitative competition: competitors consume or use the same limiting resourceÂ
But they are NOT FIGHTING FOR IT
NO AGGRESSION
Interference competition: competitors deny each other access to the limiting resources
Active competition
Interspecific competition: competition between two different speciesÂ
Intraspecific competition: competition between members of the same species
Stackables (the ones we will focus on in this class) :Â
Interspefic Explotiative
Intraspecific Interference
Intrasecic Explotitative
Interspecific Interference
Competicve exculasion principle
2 species that directly compete for resources cannot coexistÂ
Can drive one or the other into extinction
No two species can coexist using the same resources
Ecological Niche: the role an organism fills within its habitat
Fundamental niche: complete range of areas in which an organism could exist (wide range)
Realized niche: range in which an organism exists due to competition (small range)d
Analogy:Â
Fundamental niche-any career in this world (what do you want to be when you grow up)
Realized niche-what you grow up to do, not everyone can be the president because of competition, so they settle
Cant be president but can be vice presidentÂ
Niche differentiation: a smaller subset of realized niche. Going to different subsets of the resource
Species survive by dividing and sharing resources
Herbivory
Adapted to feed on plant material
Specilized digestive systems
Coevolution of herbivores and plants
Plants evolve ani0herbivory chemicals and mechanical defenses
Herbivores evolve the ability to detoxify plant chemicalsÂ
Perdition
Parasitism
Mutualism
CommensalismÂ
Biotic Interactions slide
(-) they are receiving harm from the other individualÂ
A is receiving harm from B
(+) they are receiving benefits from the other
A is receiving benefit form b
(0) no consequence of significant from the other
A does not affect B or B does not affect A
Coevolution: when two or more species reciprocally affect each other’s evolution through the process of natural selection
Species a and B
A eats b
A is going to evolve to be a better predator to eat b
B is not helpes, b can evolve to be harder to catch
Influences a to be an even better predatorÂ
(see the cycle ;) )