Populations and Communities Flashcards
Population
A group of organisms of the same species living in the same area and time that are able to interbreed with each other
Isolation Types and Descriptions
Geographic - Physical barriers that prevent interbreeding
Temporal - Differences in breeding seasons
Behavioural - Differences in mating rituals prevent interbreeding
Difficulties with Population Counting
Populations are too large to count every individual
Many organisms are mobile which makes it difficult to count them
Some organisms live in hard-to-reach places making it difficult to count them
Time and resource-heavy
Random Sampling
Studying a small part of the habitat to select a representative sample from a population to ensure everyone has an equal chance of being chosen to increase accuracy
Used when the area looks reasonably uniform and large
Quadrat Sampling Formula
Total Number of Individuals Counted / Number of Quadrats * Total Area
Standard Deviation in Quadrat Sampling
High standard deviation means greater variability in number of individuals per quadrat suggesting a less precise distribution
Low standard deviation indicates that the number of individuals per quadrat is consistent suggesting a precise and even distribution
High standard deviation indicates that resources are unevenly distributed and that species has specific habitat preferences which leads to clumped distributions in favored areas
Lincoln Index
Sample of organisms are captured from population
Organisms are marked in a way that doesn’t harm or affect behaviour
Organisms are released back into habitat
Another sample or organisms gets recaptured after some time and some will be marked from previous sample
M*N/R
Advantages and Disadvantages of Quadrat Sampling
Simple and inexpensive
Suitable for sessile organisms
Less harmful to most species
Not effective for motile organisms
Underestimates population size
Potential for error if quadrats aren’t placed or sized properly
Advantages and Disadvantages of CMRR
Suitable for motile organisms
Provides estimates of population size, survival and movement
Can be used in a wide range of habitats
More complex and time-consuming
Can disrupt population
Needs assumptions to work
Carrying Capacity and Limiting Factors
Maximum population size of a species that an environment can support over time
Environmental factors taht restrict the growth, distribution or abundance of a population or organism within an ecosystem
Density Independent and Density Dependent Factors
Affects members of a population regardless of population density (Flood, Fire, Temperature)
Affects members of a population due to its density (Competition, Resource Availability, Disease, Breeding Areas, Predation)
Population Growth Curve
Lag Phase: Period of slow initial growth as organisms adjust to environment
Exponential Phase: Populations rapidly increase due to abundance in resources and lack of competition and predation
Transition Phase: Limiting factors start to affect population size and restrict growth
Stationary Phase: Population size reached carrying capacity which slows growth rate due to limited resources
Intraspecific Competition and Reasons
When individuals of the same species compete for the same resources. This limits population growth and influences the distribution and behaviour of an individual within a population
Reasons include limited resources, increased population density and variation
Intraspecific Cooperation and Benefits
When individuals of the same species work together to achieve a common goal
Improved foraging - Individuals work together to gather and capture food
Enhanced Defense - Groups provide better protection against predators
Increased Reproductive Success - Individuals can protect offspring that aren’t their own which increases survival rate
Resource Sharing - All members of a group have enough to eat
Protection from Environment - Groups can better withstand harsh conditions
Intraspecific Competition VS Cooperation
Individuals of the same species compete for limited resources
Individuals of the same species work together for a mutual benefit
Can decrease individual fitness due to the loss of competing
Can increase individual fitness through shared benefits and reduced risks
Drives natural selection
Promotes the evolution of social behaviours
Community
A group of populations of organisms that live together and interact within a defined area
Interspecific Relationship within Communities
Herbivory - Organism consumes plant
Predation - Organisms kills and consumes another organism
Interspecific Competition - Organisms of different species compete for same resources
Mutualism - Organisms of different species interact in a way that benefits both
Parasitism - Organism lives on and harms another organisms
Pathogenicity - Infectious pathogen causes disease in a host
Root Nodules and Rhizobium
Root nodules provide a protected environment with low oxygen levels which is optimum for bacteria, as well as providing bacteria with the energy they need to survive and carry out nitrogen fixation
Rhizobium converts nitrogen gas into ammonia which the plant can use. This increased nitrogen availability allows the legume to grow faster which gives it an edge in competition with other plants
Mycorrhizae and Fungi
Orchid plant provides fungus with sugars which serves as the primary energy source for it, fueling its growth and metabolic activities
Fungus forms extensive network of hyphae to increase orchid’s ability to absorb water and essential minerals from soil. Fungus also breaks down organic matter which supplies the orchid with additional carbon compounds
Zooxanthellae and Corals
The coral’s tissue provides a protected environment for the algae which shields them, and their location and structure ensures the algae receives adequate sunlight for photosynthesis with its waste products providing algae with nutrients (Nitrogen)
Zooxanthellae provides coral sugars through photosynthesis which is crucial for growth and formation of calcium carbonate skeleton, along with oxygen and providing coral its color
Interspecific Competition VS Interspecific Cooperation
Different species compete for the same resources
Different species interact in a mutual manner
Negative for both species involved as it reduces resource availability
Positive for both species involved as it increases chance of survival and reproduction
Endemic VS Invasive Species
Naturally occurring in a specific location
Introduced to new location by humans
Regulated by density-dependent factors
Lack natural controls in new environment
Plays a balanced role in native ecosystem
Disrupts balance of ecosystem, outcompetes native species and causes ecological damage
Tests for Interspecific Competition
Labratory Experiments
Field Observations
Field Manipulation
Labratory Experiments
Field Observations
Field Manipulation
