Chapter 8: Types of Aquatic Organisms

Systematics

classifies organisms and determines their evolutionary relationship

Phylogeny

Evolutionary history of a species

Taxonomy

Classifying and naming organisms

What are the three domains of life? Which domain(s) include prokaryotic organisms? Which domain is most closely related to Domain Eukarya?

• Eukarya, Archaea, Bacteria

  • Archaea and Bacteria include prokaryotes

• Most closely related to Eukarya is Archaea

Prokaryotes reproduce asexually but can still exchange genetic material.

What process allows this exchange?

Horizontal Gene Transfer (HGT)

• Define speciation. Does the process of evolution always lead to speciation? Explain.

• Speciation – process in which one species split into two or more species

• The process of evolution does NOT always lead to speciation because speciation requires reproductive isolation and genetic divergence.

What is the definition of a species under the biological species concept? Under this concept, what is required for the formation of a new species? Explain.

Biological species concept – defines a species as a group of populations whose members have

1. potential to interbreed with one another

2. produce viable, fertile offspring

What are some limitations to the biological species concept?

Does not work on

• Asexual

• Dead organisms (fossils)

Why are genetic methods commonly used to identify prokaryotic species instead of morphological characteristics?

Prokaryotes lack physical diversity for identification

What are Operational Taxonomic Units (OTUs), and how are they used to classify microorganisms?

Sequences that classify microorganisms based on genetic similarities

Give some examples of how biochemical or molecular traits can be used to classify organisms.

• DNA and RNA sequences

• Amino acid sequences

What types of genetic material can be used in molecular analyses to identify and classify organisms?

• DNA

• rRNA

• mRNA

Why is ribosomal RNA (rRNA) commonly used for identifying and comparing species?

Ribosomal RNA is highly conserved

What is the difference between conserved regions and variable regions in rRNA, and why are they important for classification?

• Highly conserved regions are essential to function and remain the same

• Variable regions are not essential and change more rapidly

Allows for identification of unknown bacteria in mixed samples

Why are conserved regions useful for primer binding, while variable regions are useful for identifying species differences?

• Conserved regions (sequences don’t change) and scientists can design a universal primer to DNA of almost any organism

• Variable regions are located in conserved segments and have unique patterns to determine species

What is environmental DNA (eDNA), and how is it used to determine the presence or absence of a species in an environment?

Environmental DNA (eDNA) refers to the genetic material shed by organisms into their environment

• It can include cells, tissues, or water products from a species that reveal that a species is present

What are some practical applications of eDNA?

• Identify invasive/endangered/rare species

• Identify disease-causing or water-quality impairing organisms

Prokaryotes are often described as “highly evolved.” What does this mean in this context?

They are highly successful at evolving and adapting and have done so for 3.5 billion years

What is the endosymbiotic theory? What evidence supports this theory?

Endosymbiotic theory proposes that mitochondria and chloroplasts evolved from endosymbiotic prokaryotes living inside a host eukaryotic cell.

• Evidence: Mitochondria and chloroplast have similarities to bacteria – enveloped in double membrane, contain own DNA, free ribosomes, and grow and reproduce independently

What is the difference in how the different algal groups (green, red, and SAR clade algae) evolved the ability to carry out photosynthesis? Distinguish between primary and secondary endosymbiosis.

• Primary endosymbiosis (traditional) – a eukaryotic cell engulfed a bacteria cell (taking in a bacteria cell directly – red, green algae)

• Secondary endosymbiosis – engulfed a red or green algal cell to carry out photosynthesis

Why do some organisms need oxygen? Explain the difference between aerobic and anaerobic organisms.

Oxygen serves as the last electron acceptor

• Aerobic – require oxygen to survive

• Anaerobic – do not require oxygen

How are organisms classified nutritionally? What two factors are used?

Classified upon how they obtain energy and carbon

What carbon source do autotrophs use?

Carbon dioxide (CO2)

How do photoautotrophs differ from chemoautotrophs?

• Photoautotrophs obtain energy from light

• Chemoautotrophs obtain energy from chemicals (sulfur, ammonia, iron)

What are functional feeding groups? How do dominant functional feeding groups change from headwaters to downstream waters?

Functional feeding groups are classification based on how organisms obtain food

• The trend moves from Shredders/Gatherers (headwaters) to Scrapers(mid-stream) and finally to Collector-filterers (downstream).

What type of organic matter do shredders consume, and where are they most abundant?

Shredders consume CPOM (coarse) – leaves and wood

• Abundant at the bottom of headwaters

What type of organic matter do collectors and filterers consume, and where are they most abundant?

• Consume live/dead drifting organisms

• Dominant in downstream waters

What is a biofilm? What types of organisms are typically found in a biofilm? Where are biofilms commonly found in aquatic ecosystems?

• Biofilm – microbial community that includes bacteria, unicellular organisms, protists, fungi, algae

  • Biofilms are commonly found on any substrate

What do grazers (scrapers) feed on? What type of mouthparts do grazers use?

• Biofilm

• Rasping mouthparts (specialized mandibles, radula)

What are interspecific interactions? Describe how the following interactions affect both species (+, -, 0) for competition, mutualism, commensalism, amensalism, neutralism, and exploitation.

Competition (-/-): costly for both species

Mutualism (+/+): both species benefit

Commensalism (+/0): one species benefits, the other is unaffected

Amensalism (-/0): one species is harmed, the other is unaffected

Neutralism (0/0): neither species affected (rare)

Exploitation (+/-): one species benefits, the other is harmed

What types of interactions are included under exploitation.

Predation: one animal kills and eats another

Herbivory: animal eats a part of a plant

Parasitism: parasite lives on host without immediately killing it

What is the competitive exclusion principle?

Competitive exclusion principle – states that if two species have an ecological niche that is too similar, the two species cannot coexist in the same place

Can two species with identical ecological niches coexist long-term? Explain why or why not.

No, because it is statistically impossible for two different species to be exactly equal in their ability to acquire resources, even a tiny advantage will allow one species to take over