ECOLOGY 4.1: Species, Communities and Ecosystems

SPECIES

 a group of organisms that can potentially interbreed with one another and produce fertile offspring

WHY CANT SPECIES TOO CLOSELY RELATED PRODUCE FERTILE OFFSPRING?

When species are too closely related, they may produce offspring with genetic abnormalities that can lead to infertility or reduced fitness. This is because closely related species have similar genetic material, which can result in errors during meiosis and fertilisation. Why? because both parents have different numbers of chromosomes. Even if the chromosome numbers happen to be the same, the DNA is usually too different and so fertilization of gametes is not possible.​ Eg: Liger or mule

POPULATION

a group of organisms of the same species that live in a particular area at the same time

WHAT IS REPRODUCTIVE ISOLATION?

Reproductive isolation prevents interbreeding and gene flow between different species or populations.

can occur due to:

* Geographical barriers​
* Temporal isolation (mating seasons don’t coincide)​
* Ecological isolation (live in different habitats, eat different food, etc)​
* Behavioural isolation (don’t know the other’s mating ritual)​

If these organisms would still be able to functionally interbreed then they are still considered the same specie. But, R.I often leads to **speciation** - the isolated organisms evolve until they form a new species that is unable to breed with the original specie

COMMUNITY

groups of populations living and interacting in the same area 

ECOSYSTEM

a community and its abiotic factors

ABIOTIC FACTORS

non-living factors Eg: pH, salinity, windspeed etc

BIOTIC FACTORS

living factors in an ecosystem Eg: plants and animals

AUTOTROPHIC

organisms that are capable of making their own organic compounds from carbon dioxide and other simple compounds​

HETEROTROPHIC

organisms that obtain organic compounds from feeding on other organisms. ​

MIXOTROPHIC

can feed both autotrophically and heterotrophically​

WHAT IS AUTOTROPHIC IN THE FOOD CHAIN?

 producers

WHAR ARE HETEROTROPHIC IN THE FOOD CHAIN?

​consumers by ingestion . They can range from apex predators such as sharks and lions, to *Paramecium* that take in their food by endocytosis.​

INGESTION

is the taking in of a substance (solid or liquid food, medication, toxic substances, etc)​

DIGESTION

breaking down food once it has been ingested​

ASSIMILATION

the absorption of nutrients and transport to the cells of an individual.

EGESTION

waste or undigested material that leaves the body​

HERBIVORES:

feeds on only plants. primary consumers.

CARNIVORE

feeds on only animals. secondary consumers -

OMNIVORE

feeds on both plants and animals. secondary consumers -

DETRITIVORES

* obtain their nutrients from detritus: waste or other organic debris.​


* skin and hair shed from humans, feathers from birds, leaves and flowers from plants, faeces, dead or decaying organisms.​
* obtain these nutrients via **internal digestion**: they have an internal digestive tract wherein their food is broken down.​ ESSENTIAL FOR NUTRIENT CYCLING
* Eg: dung beetles and earthworms

SAPROTROPHS

* obtain their nutrients from dead organisms through **external digestion**.​
* Eg: Fungi and bacteria ​
* Often called **decomposers** as they break down dead and decaying matter​
* secrete digestive enzymes on decaying organic matter and break it down into simple organic compounds. ESSENTIAL FOR NUTRIENT CYCLING
* These are then absorbed by the saprotrophs for nutrition and by the soil to be recycled by plants.​

TYPES OF RELATIONSHIPS BETWEEN POPULATIONS IN A COMMUNITY?

* **Mutualism/ symbiotic relationship:** where both organisms benefit​
* **Commensalism**: where one organism benefits and the other is unaffected​
* **Parasitism:** where one organism benefits and the other is harmed​

WHAT IS AN EXAMPLE OF A MUTUALISM/ SYMBIOTIC RELATIONSHIP?

spider crab and algae. Algae get a place to live on the back of the spider crab and the spider crab gets camouflage from predators.​

WHAT IS AN EXAMPLE OF A COMMENSALISM RELATIONSHIP?

a birds nest in a tree. The bird has a safe place to build its nest and the tree neither benefits nor is harmed by the nesT

WHAT IS AN EXAMPLE OF A PARASITISM RELATIONSHIP?

mosquito and humans. Mosquitoes feed off human blood but cause itchy bites and sometimes spread  disease in humans.

EXAMPLES OF ABIOTIC FACTORS?

* Rainfall​


* Temperature​
* pH of water/soil​
* Wind​
* Humidity

HOW DOES NUTRIENT CYCLING WORK AND PRODUCE A SUSTAINED ECOSYSTEM?

* Autotrophs synthesize organic compounds from simple, inorganic nutrients they obtain from the abiotic environment.​
* Nutrients are transferred from one organism to the next through the food chain.​


* Nutrients are released back into the abiotic environment via decomposition and other processes (e.g. respiration) and recycled by other living organisms.​
* Nutrient cycling is essential for maintenance of a healthy ecosystem.​
* If conditions are sustainable, these nutrients can be recycled almost indefinitely.​

HOW DO AUTOTROPHS SUPPLY FOR THEIR ENVIRONMENT?

* energy cannot be recycled in an ecosystem so it must be constantly supplied. ​
* For most ecosystems, this energy comes from the Sun. 
* **Photoautotrophs** synthesize organic compounds (glucose) from sunlight which lay the foundations for an ecosystem. ​
* Some ecosystems, e.g. those in the deep ocean, cannot rely on sunlight for energy. Instead, **chemoautotrophs** synthesize organic compounds using chemical energy.​
* As long as an ecosystem has sufficient energy and nutrient cycling, it can sustain itself for a very long time.
* However, human activities that use resources faster than they can be replenished are threatening many different ecosystems, including some that have existed for millions of years.​

HOW DO AUTOTROPHS OBTAIN INORGANIC NUTRIENTS FROM THEIR ENVIRONMENT?

* Living organisms require a supply of various chemical elements like carbon, hydrogen, oxygen, nitrogen and phosphorous etc.
* Autotrophs obtain these from their abiotic environment (i.e. gases in the atmosphere (CO2, O2), soil (nitrates, phosphates), water (Mg2+. K+)).​
* Heterotrophs obtain their nutrients from the carbon compounds in the food they consume. They also obtain some (e.g. sodium, potassium and calcium) from the abiotic environment.​

HOW DO QUADRATS WORK?

* useful tools for sampling areas of interest when investigating ecosystems.


* can vary from 10cm2 to 1m2: the size chosen will depend on the organisms being counted.
* usually square but can come in a number of shapes. ​