Chapter 4.1 Species, communities, and ecosystems Flashcards Preview

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Flashcards in Chapter 4.1 Species, communities, and ecosystems Deck (28):


groups of organisms that can potentially interbreed to produce fertile offspring. Members of a species may be reproductively isolated in separate populations. Members of the same species have a common gene pool



organisms capable of making their own organic molecules as a source of food. Synthesize their organic molecules from simple inorganic substances --> photosynthesis. They can take light energy from Sun, combine it with inorganic substances and obtain a source of chemical energy in the form of organic compounds. --> PRODUCERS. Can make food by using carbon dioxide, water and sunlight. They start the food chain



organisms that cannot make their own food from inorganic matter, and must obtain organic molecules from other organisms --> get chemical energy from autotrophs or other heterotrophs --> CONSUMERS. They take energy-rich compounds such as sugars, proteins and lipids synthesized by other organisms. (Vitamin D excluded)



heterotrophs that feed on living organisms by ingestion



heterotrophs that obtain organic nutrients from detritus by internal digestion



heterotrophs that obtain organic nutrients from dead organisms by external digestion



formed by populations of different species living together and interacting with each other. It forms an ecosystem by its interactions with the abiotic (non-living) environment. Interacting can mean 1 population feeding on another, or being eaten, or one provides vital substance for another (symbiotic bacteria)



obtain inorganic nutrients from the abiotic environment


Nutrient cycling

this maintains the supply of inorganic nutrients. Ecosystems must recycle the carbon, nitrogen and other elements and compounds necessary for life to exist. Organisms must find what they need within the materials available in their own habitat. They absorb valuable minerals and organic compounds and use them to build their cells.



a community of living organisms in conjunction with the nonliving components of their environment. Abiotic (non-living like water, air and rocks) measurements are taken of an environment, they include temperature, pH, light levels and relative humidity in the air. have the potential to be sustainable over long periods of time. --> way to measure this is random sampling (quadrat)


Interdependence of living organisms

1980: major volcanic catastrophe at Mount Saint Helens in US. Little was left of the forest and rivers that had existed on and around. Within months of the eradication of the ecosystem, life was back. Seeds germinated in the fertile volcanic ash. Gradually insects, birds and small mammals moved in, and grassland and shrub ecosystem has reappeared a couple decades later


What is a species?

-interbreed and produce fertile offspring
-members of same species have a common gene pool
- species is the basic unit for classifying organisms:
1. similar physiological and morphological characteristics that can be observed and measured
2. can interbreed to produce fertile offspring
3. genetically distinct from other species
4. have a common phylogeny (family tree)


Special cases for species

Hybrids: 2 separate but similar species mate and produce successful hybrid offspring. Horse and Zebra --> Zebroids. Don't have the same number of chromosomes --> infertile



Two different but similar species mate and produce offspring. Horse and Donkey --> Mule. However, mules cannot mate to make more mules, no new species has been created because they are infertile. Called an interspecific hybrid


Isolated Populations

If a group from a species is separated from the rest of the species, it might evolve differently. Mice have crossed oceans after going on board ships looking for food, and a new population develops on new territory. Compared with the original population on the mainland, an island population of mice may end up with different frequencies of certain alleles for a trait such as fur colour. Over time this may lead to speciation, a new species is formed from an old one.


Examples of Autotrophs

cyanobacteria, algae, grass, trees


Examples of Heterotrophs

zooplankton, sheep, fish, insects



Some organisms eat non-living organic matter, they eat dead leaves, faeces, and carcasses. Earthworms, woodlice and dung beetles are examples.



Organisms that live on or in non-living organic matter, secreting digestive enzymes and absorbing the products of digestion. --> DECOMPOSERS, they break down waste material. ex: mushrooms secrete energy molecules into dead tissue of tree trunk, absorb simpler energy rich carbon compounds that are released by action of the enzymes, slowly over time tree trunk decomposes as the molecule inside the wood are liberated and reused
Decomposers recycle nutrients so that they are available to other organisms, play a major role in the formation of soil (humus) made of organic debris and nutrients released by decomposers.


Symbiotic Bacteria

help certain plants get nitrogen while the bacteria grow in the plant root nodules, one species gets protection from another as in the case of aphids being protected by ants from attacks by predators.


Random Sampling

Quadrat is a square of particular dimension made of rigid material, a table of random numbers from 1 to 99. Counting species in that area


Systematic sampling techniques

Using a transect, a line traced from one environment to another such as from a grassland into a woodland. Laying down a quadrat and then counting the organisms found within each one.


Chi squared test: critical value p 797

X2 calculated reject Ho
X2 calculated > X2 critical --> accept Ho


Sustainability of ecosystems

Due to recycling of nutrients, ecosystems can continue to be productive, producers take simple inorganic compounds (CO2) and convert them into energy rich sugars (glucose). Those simple sugars can be transformed into complex carbohydrates to make cellulose, to build up plant cell walls. Other nutrients can be added to form complex organic molecules such as lipids and proteins.
Consumers will then eat producers, digesting the complex organic compounds into simpler building block (amino acids and sugars) for growth and energy. When those consumers die, their cells and tissues are broken down by decomposer and the minerals are returned to the soil. Producers can once again absorb the nutrients from the soil and grow new sources of food.


Nitrogen Cycle

Nitrogen is extremely important to living organism, as it is one of the elements needed in nucleotides and amino acids, building blocks of life. Nitrogen starts the cycle in gas form in the atmosphere (N2). Plants and animals are incapable of using nitrogen gas bust some bacteria are able to transform it into nitrates in a process called nitrogen fixation. These usable nitrates are absorbed by plant roots and so the plants pass on nitrogen-rich nutrients when they are consumed by animals. Both plants and animals return the nitrogen to the soil in different ways (urine, faeces). When plants and animals die, nitrogen compounds are returned to the ground by decomposition



Place where an organism or a biological population normally lives or occurs.


Products of Autotrophs for Humans

fruits and vegetables


Products of Heterotrophs for Humans

meat, eggs, honey and dairy products