2.1 - Species And Populations Flashcards
What is a species
A species is a group of organisms sharing common characteristics that interbreed to produce fertile offspring
Members of the same species share a gene pool, meaning that they can breed and produce offspring with similar traits
What is a habitat
A habitat is the environment in which a species normally lives
What can habitats be characterised as
Abiotic or biotic factors
How do organisms adapt to their habitat
Organisms adapt to their habitat through natural selection, in order to survive and reproduce successfully
What is a niche
A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds
How many species can occupy a niche
A niche can only be occupied by one species, meaning that every individual species has its own unique niche
What happens is 2 species try to occupy the same niche
If two species try to occupy the same niche, they will compete with each other for the same resources
One of the species will be more successful and out-compete the other species until only one species is left and the other is either forced to occupy a new, slightly different niche or to go extinct from the habitat or ecosystem altogethe
Define fundamental niche
The full range of conditions and resources in which a species could survive and reproduce
Define realised niche
The actual conditions and resources in which a species exists due to biotic interactions
Define abiotic factor
The non-living, physical factors that influence ecosystems and the communities of organisms within them are termed abiotic factors
What are some examples of abiotic factors
Temperature
Sunlight
pH
Salinity
Precipitation
What can changes in abiotic factos do to organisms
Changes in abiotic factors can affect the survival and reproduction of organisms, and the overall functioning of ecosystems
How can light intensity affect a community
Light is needed by plants for photosynthesis. More light leads to an increase in the rate of photosynthesis and an increase in plant growth rates.
How can temperature affect a community
Affects the rate of photosynthesis in plants. Also affects the rate of metabolism, growth and reproduction of organisms. Certain species have adapted to specific temperature ranges and cannot survive outside of those ranges.
How can moisture and precipitation levels affect a community
Determines the amount of water available to organisms, which can impact their survival, growth and reproduction. Some species are adapted to areas with high precipitation, while others are adapted to arid environments.
How can soil and mineral content affect a community
Different species of plants are adapted to different soil pH levels and nutrient concentration levels.
how can wind intensity affect a community
Wind speed affects the transpiration rate in plants. Transpiration affects the rate of photosynthesis as it ensures water and mineral ions are transported to the leaves.
How does carbon dioxide levels for plants affect a community
CO2 is required for photosynthesis in plants. CO2 concentration affects the rate of photosynthesis.
How does water chemistry affect a community
Affects the health and survival of aquatic organisms, particularly those that are sensitive to changes in pH, salinity, and dissolved oxygen levels. Some aquatic animals, such as fish, can only survive in water with high oxygen concentrations.
What are biotic factors
The living, biological factors that influence ecosystems and the communities of organisms within them are termed biotic factors
In other words, biotic factors are the interactions between the organisms within a community
What are some examples of biotic factos
Competition
Predation
Herbivory
Parasitism
Mutualism
Disease
What does biotic factors affect in a community
These biotic interactions mean that each species in an ecosystem has an influence on the population dynamics of the other species
What is a population
A population is a group of organisms of the same species living in the same area at the same time
Populations can be characterised by their size, density, distribution, age structure, and growth rate
What is a carrying capacity
The carrying capacity of a habitat or ecosystem is the maximum number of individuals of a particular species (i.e. the maximum population size) that can be sustained in a given area over a given time period
What is infraspecific competition
competition between members of the same species
What is interspecific competition
competition between members of different species
How does intrasepcific competition affect a population
Intraspecific competition can lower the carrying capacity of a population due to a decrease in food availability caused by high population density
What does interspecific competition do to a population
Interspecific competition occurs between species with similar niches, causing a decrease in the carrying capacity of one or both species
What predation
- When one animal eats another
- This lowers the carrying capacity of the prey species
- This can have negative feedback effects, lowering the carrying capacity of the predator species due to a decrease in prey numbers
What herbivory
When an organism (known as a herbivore) feeds on a plant
The carrying capacity of herbivore species is affected by the quantity of plants they feed on
An area with more plant resources will have a higher carrying capacity for herbivore species
This can also have negative feedback effects - the carrying capacity of the herbivore species may decrease if herbivory rates are too high and the plant population decreases too much
What is parasitism
- Parasites are organisms that are adapted to live very closely with another species, known as the host species
- A parasitic relationship is one in which the parasitic organism benefits from the host organism
- The parasite lives either in or on the body of the host species and gains resources (i.e. what it needs in order to survive) from the host, including food, shelter and a suitable location to reproduce (where offspring can feed and grow)
- However, the host does not benefit from this relationship and parasites often harm the host in some way
- This can lower the host’s carrying capacity
What is mutualism
- mutualistic relationship between species is one in which both species benefit
- This increases the carrying capacity of both species in the relationship
- An example of a mutualistic relationship is the one that exists between bees and many species of flowering plants
- Bees gain nectar (i.e. food to provide them with energy) from flowers
- When bees visit flowers, pollen is transferred to their bodies
- As bees visit multiple different flowers, they spread the pollen to these flowers, pollinating them
- In this way, the flowers gain help in reproducing
What is a disease
- Pathogens (bacteria, viruses, fungi, and protozoa) are organisms that cause diseases
- These diseases lower the carrying capacity of the species that the pathogens infect
- Changes in the incidence of diseases can cause populations to fluctuate around their carrying capacity
What is a limiting factor
Limiting factors restrict the growth of a population (prevent it from increasing further)
- Plant populations have several limiting factors, including light, nutrients, water, carbon dioxide, and temperature
- Animal populations have several limiting factors, including space, food, mates, nesting sites, and water
How will limiting factors affect the growth of a population
Limiting factors will slow the growth of a population as it approaches the carrying capacity of the system
What are s and j curves
S and J population curves describe a generalised response of populations to a particular set of conditions (abiotic and biotic)
What is a s population curve
- For most populations, when population growth is plotted against time, an S-population curve is produced
- An S-population curve describes the growth pattern of a population in a resource-limited environment
- The S-population curve has four distinct phases
What are the 4 stages of the s population curve
- Lag phase
- Exponential growth
- Transitional phase
- Plateau phase
What is the lag phase
The initial growth is slow when the population is small
What is the exponential growth phase
With low or reduced limiting factors, the population expands exponentially into the habitat
What is the transitional phase
As the population grows, there is increased competition between individuals for the same limiting factors or resources - this competition results in a lower rate of population increase
What is the plateau phase
The population reaches its carrying capacity and fluctuates around a set point determined by the limiting factors - changes in limiting factors cause the population size to increase and decrease (these increases and decreases around the carrying capacity are controlled by negative feedback mechanisms)
What is a j population curve
- For some populations, when population growth is plotted against time, a J-population curve is produced
- A J-population curve describes the growth pattern of a population in an environment with unlimited resources
- The J-population curve has three distinct phases
What are the 3 phases of a j curve
- The lag phase
- The exponential growth phase
- The crash phase
What is the lag phase
The initial growth is slow when the population is small
What is the exponential growth phase
- Population growth accelerates exponentially as the number of individuals increases
- The curve takes a J-shape due to exponential growth, as resources are not limiting the growth of the population
- The population will continue to grow until a limiting factor such as disease or predation occurs
What is the crash phase
At this point, if there has been a significant population overshoot (the population has increased far beyond the natural carrying capacity), there may be a sudden decrease in the population, known as a population crash
Compare s curves and j curves
- Both curves show how populations grow and reach a carrying capacity
- The S-curve occurs in a limited environment, while the J-curve occurs in an unlimited environment
- The S-curve represents logistic growth, while the J-curve represents exponential growth
- The S-curve eventually levels off at the carrying capacity, while the J-curve continues to increase until a limiting factor is encountered
- The S-curve is more common in nature, while the J-curve is less common and is often observed in laboratory conditions
