Final Unit 2
Unit 2
Population ecology: how populations interact with their environment
Includes birth, death rates, and immigration and emigration
How do population sizes change through time
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 environment
Both are unrealistic because of the presence of diseases, predators, etc..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:
take 70 ➗the percentage
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)
Exponential Growth Formula: (take from slideshows)
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
A more realistic pattern of growth
Logistic growth: occurs when resources are limited,d thereby setting a maximum number an environment can support
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
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
Survivorship: the probability of an organism dying during a particular interval
Species survival varies widely
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 resources
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 are
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 mechanism
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 desirable
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 reproduction
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
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)
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
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.
Genetic drift is completely random.
A change in the frequency of an inherited trait that is caused by a chance event
Non-adaptive evolution (not caused by fitness)
Random evolution (not caused by adaptive traits)
Founder effect: type of genetic drift
A change in the frequency of an inherited trait that is caused by a small subset of the population
Productive isolation: members of one species do not interbreed with members of other species ( breeding barriers)
A hybrid between two species are often sterile, like the mule
Types of reproductive isolation
Geographic isolation: Separateded by space
Keeping to their known environments
Temporal isolation
Time
Matting at different times
Behavioral isolation
Courtships
singing, dancing, body posture
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
The flipside of evolution and speciation is extinction
Mass extinction:
In a short period, planet-wide
Background Extinction:
The average rate of extinction between mass extinction events; is always occurring.
Species that cannot evolve and adapt to a changing environment are designed to go extinct.
We are possibly in a 6th major extinction event, which humans may cause
Pre- agricultural Period
Demographic Transition Model
The more developed nations have lower birthrates
Lower birth rates correlate to higher GDP
Age structure
Determined by survivorship and age-specific birth rate
Population of 8.1 billion people on the planet
9 million in 15 years
Human population growth is exponential
Ecological footprint: area of land needed to supply resources consumed by people
Includes: cropland, grazing, forests, fisheries, carbon footprint, but-up land, water, and waste disposal
Suitability vs caring capacity
Carrying capacity is the size of the population that an environment that can support
Human resources use
Biocapacity: area and quality of land available to supply resources
Population whose ecological footprint exceeds their capacity must have goods imported
Ecological debtors
Populations whose biocapacity exceeds their ecological footprint may export goods: ecological creditors
Community Ecology:
Definition: examines how organisms in a community interact with each other and their environment
Community: a group or association of population of two or more different species occupying the same geographical area and in a particle time
Six categories of how they interact with each other
Competition (Biological)
The fitness (biological fitness) of each group is reduced when they occur together
No matter what both parties lose fitness because when they spend time competing( competing is a limiting factor when it comes to fitness)
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 resource
NO AGGRESSION
Interference competition: competitors deny each other access to the limiting resources
Active competition
Interspecific competition: competition between two different species
Intraspecific competition: competition between members of the same species
Stackables (the ones we will focus on in this class) :
Interspefic Explotiative
Intraspecific Interference
Intrasecic Explotitative
Interspecific Interference
Competitive exclusion principle
2 species that directly compete for resources cannot coexist
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)
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
Specialized digestive systems
Coevolution of herbivores and plants
Plants evolve herbivory chemicals and mechanical defenses
Herbivores evolve the ability to detoxify plant chemicals
Predation
Parasitism
Mutualism
Commensalism
Coevolution: when two or more species reciprocally affect each other’s evolution through the process of natural selection
Unit 3
Ecosystem: A biological community of interacting organisms and their physical environment
Energy: The qualitative property that must be transferred to an object to perform work on, or heat the object.
It flows through ecosystems (transforms)
Energy is finite; it moves and flows.
Photosynthesis: the process of using light energy to convert carbon dioxide (inorganic carbon) to carbohydrates (organic carbon)
Plants and algae
Light to food conversion
Cellular respiration: the process of breaking down the chemical bonds in food molecules (organic carbon) to harvest energy and release carbon dioxide (inorganic carbon)
Food chain: a hierarchical series of organisms, each dependent on the lower level as a source of food
Primary producers/1st trophic level
Transform energy from the sun
Primary consumers/2nd trophic level
Herbivores
Secondary consumers/3rd trophic level
Predators (carnivores)
Tertiary consumers/4th trophic level
Predators (carnivores)
Decomposers Feed on nonliving organic matter
Feces/dead organisms
Food web: the natural interconnection of food chains and a graphical representation of what