4.1 Species, communities and ecosystems Flashcards
Species
A group of genetically similar living organisms that are able to interbreed and produce fertile offspring
Gene pool
A collection of genes found in a population. All members of a species have a common gene pool
Fertile offspring
Those which can interbreed and pass on their genes to another generation
Why aren’t mules considered a species?
They are infertile possibly because they have odd number of chromosomes (64 from horse and 62 from donkey comes to 63 in mules)
Population
A group of members of the same species living together in the same place at the same time
Communities
Groups of different populations living and interacting in a particular area
Ecosystem
A community and its abiotic environment
Habitat
The environment in which a species normally lives
Abiotic factors
Non-living factors like salinity, wind speed, type of soil, pH of water
Biotic factors
Living factors like plants and animals
What is the order of grouping? i.e. Species
Species Population Community Ecosystem Biome Biosphere
Autotrophs
Organisms that are capable of making their own complex organic molecules from carbon dioxide and water eg. Plants
Heterotrophs
Organisms that obtain their organic compounds by feeding on other organisms
Are bacteria, protoctista and fungi auto or heterotrophic?
Protoctista and bacteria can be both while fungi is heterotrophic
What do you call organisms which feed both autotrophically and heterotrophically?
Mixotrophs
Give an example of a mixotroph
Euglena and venus flytraps. Both undergo photosynthesis and endocytosis
What are the 3 type of heterotrophs?
- Consumers
- Detritivores
- Saprotrophs
Consumers
Organisms that gain nutrients by feeding on other organisms using ingestion or absorption
How do consumers like Paramecium take in their food?
Through endocytosis. They digest it in food vacuoles using lysosomes
Why are parasites considered consumers?
They rely on host to break down food for them and then they absorb it through their skin.
How can consumers be further divided?
Primary/secondary consumers, herbivores and carnivores etc.
Detritivores
Organisms that gain nutrients by feeding on dead organic material (detritus) and breaking it into smaller organic molecules
Example of detritivores
Earthworms, woodlice, dung beetles
What does it mean when we say detritivores use ‘internal digestion’?
It is the process by which it digests food inside of its body, usually with the aid of a digestive tract
How are detritivores important to the environment?
They are important for recycling nutrients and returning them to the soil for autotrophs to use
Examples of detritus
Hair, skin cells, faeces, feathers, remains of decaying bodies
Saprotrophs
Organisms that get their nutrients by secreting enzymes into their environment to break down organic debris around them
What is external digestion?
The process by which organisms break down external nutrients outside and then absorb them in
Why are saprotrophs not consumers?
They do not ingest food
Why is nutrient cycling important?
To sustain ecological stability
Main difference between saprotrophs and detritivores
Saprotrophs perform external digestion while detritivores perform internal digestion
Symbiosis
Means “living together” and it refers to the outcomes of interactions between populations
Mutualism
Symbiotic relationship which benefits both organisms
Example of mutualism: Spider crabs and algae
The algae lives on the crab’s back. This camouflages the crab from predators while algae gets a place to live
Commensalism
A symbiotic relationship where one organism benefits and the other is unaffected
Example of commensalism
Birds building their nest in a tree
Parasitism
Symbiotic relationship where one organism benefits and other is harmed
Example of parasitism
Mosquitos and humans. Mosquitos depend on human blood while humans are uncomfortable and can even contract diseases
Communities and their interactions are complex. Briefly outline how introduction of wolves to a park of deer can change ecosystem (even changing the course of river)
- Large amounts of deer= less vegetation=more soil erosion
- Wolves reintroduced= reduction of deer and hence change in behaviour (eg. avoiding certain parts of park)
- Vegetation regrew, soil stabilized and banks stopped collapsing= change in course of river
Predator-prey relationship
One in which one organism hunts and feeds on another
Why are abiotic environments like Antarctica impossible to live in except for few organisms?
Temperatures can be too low (-80C in Antarctica) or too high and there may be harsh conditions like no light for upto 6 months. Organisms that do survive have to have special adaptations
What elements do organisms need to make complex compounds?
Carbon sources, P + N for nucleic acids, S for proteins and so many more. (Eg. Mg for bones and selenium for enzymes)
Why are coral reefs and tropical jungles ideal?
They have ample food resources and sufficient inorganic nutrients
How do self-sustaining environments remain sustainable?
- Continuous energy availability
- Nutrient cycling
- Recycling of waste (eg. breaking down toxic molecules)
Photoautotrophs vs. chemoautotrophs
One uses energy from sun for photosynthesis while other relies on chemical energy to make organic compounds
How does nutrient cycling help food chain?
It moves organic molecules and mineral through the food chain and back into soil where it can be re-entered through reuptake in plants
Mesocosm
Tool used to model ecosystems in order to monitor and evaluate variables and their effects. Energy enters and leaves but matter doesn’t
What do mesocosms evaluate?
Evaluates how organisms and communities might react to environmental change through manipulation of environmental variables
Advantages of a mesocosm
- Treatments are easily replicated
- Effect of many environmental factors can be tested
- Direct and indirect effects can be studied
- Contamination influence can be studied and evaluated
- Constants can be controlled to see effect on one factor at a time
- Sustainability can be tested
Chi squared tests
A form of statistical analysis that determines how likely an observed distribution is due to chance
How does chi squared tests help evaluation?
They help better understand communities and whether two populations are associated and dependent upon each other or not
What type of hypothesis does chi-squared tests test?
“Goodness of fit”
Ecological frequency
Number of times a plant species occurs in a given number of quadrats. Usually expressed as a percentage
Expected frequency
Number of quadrats a population is expected to occupy in an area
Degrees of freedom
Number of rows minus one into number of columns minus one.
What is the common p value accepted for implication that variables are dependent?
It is commonly accepted that p value should be less then 0.05 for it to imply variables are dependent
Limitations of chi squared tests
○ Can only be used for categorical data
○ Data must be raw data counts, not percentages or continuous data
○ Not valid if sample size is small value, eg. One organism
○ Cannot tell you what the association between the variables is
What is quadrat used for and what shape can they be?
Can also use a quadrat to see how many organisms fall in a part of the grid. Quadrat can be of any size or shape but usually a square
Why is random sampling necessary?
Random sampling is necessary to obtain data that is random and unbiased and where every organism or subject has equal chance of being part of sample
Formula for chi squared tests is: X^2=Σ * (O−E) 2 /E What does each variable mean?
- X^2 is test statistic
- Σ Is the sum of (i.e. using formula for all values in table)
- O= observed frequencies
- E= Expected frequencies
