Bacteria, Protists, Fungus, and Animal Diversity

Groups to know: Domain Bacteria, Domain Archea. Which is more closely related to Domain Eukarya? Which is the outgroup?

Domain Archaea is more closely related to Domain Eukarya based on molecular and genetic similarities such as similar RNA polymerases, histone-like proteins, and shared metabolic pathways.

Domain Bacteria is the outgroup as it diverged earlier from the ancestor of all 3 descendants and lacks the commonalities of Archaea and Eukarya.

What do scientists believe was the genetic material in the most ancient organisms?

Scientists believe that DNA was the genetic material in the most ancient organisms.

What energy and carbon sources are used by prokaryotes?

Photoautotrophs:

• Energy Source: Light

• Carbon Source: CO2, HCO2-

Chemoautotrophs:

• Energy Source: Inorganic Chemicals

• Carbon Source: Co2, HCO3-

Photoheterotrophs:

• Energy Source: Light

• Carbon Source: Organic Compounds

Chemoheterotrophs:

• Energy Source: Organic Compounds

• Carbon Source: Organic Compounds

Approximately when did photosynthesis evolve in bacteria? How did this change the composition of Earth’s atmosphere?

Photosynthesis evolved in bacteria around approximately 2.7 billion years ago. This changed the composition of Earth’s atmosphere through oxygen production (which is when the oxygen produced dissolved in the surrounding water and then began to gas out and enter the atmosphere), formation of iron oxide(from oxygen reacting with iron in water), and oxygen revolution (oxygen levels increased gradually and rapidly)

Define and distinguish between conjugation, transformation, and transduction. Why are these important processes?

Conjugation: direct transfer of DNA between two prokaryotic cells that are temporarily joined. It is through cell to cell contact using a pilus in which a donor cell transfers plasmid DNA to a recipient which spread antibiotic resistant genes.

Transformation: uptake of foreign DNA from the environment by a prokaryotic cell. In other words, a cell takes up DNA fragments from its surroundings and incorporates them into its own genome through homologous recombination.

Transduction: transfer of DNA from 1 bacterium to another via bacteriophages. During this phage, bacterial DNA is package into a phage particle and transferred to a new host cell

These are important processes because they facilitate the spread of genetic traits, increase genetic diversity, and promote bacterial variation and can spread beneficial genes.

Groups to know: Domain Eukarya. You do not need to know the groups within eukarya.

They encompass all organisms with membrane bound organelles, nucleus and linear chromosomal DNA.

It includes animals, protists, fungi and plants. It contains larger and more complex cells that undergo mitosis and meiosis, autotrophic/heterotrophic, and have evolved from archaea-like ancestors.

Are protists eukaryotic or prokaryotic organisms?

Eukaryotic organisms because they have membrane-bound organelles and a nucleus.

What was the role of endosymbiosis in the rise of the eukaryotes?

Endosymbiosis is when one organism lives within another. It explains how eukaryotic cells developed through prokaryotic ones.

Mitochondria formation: A larger archael-like host cell engulfed an oxygen bacteria(also known as a protobacterium). Instead of digesting it like a parasitic relationship, the host and bacterium provided a mutualistic relationship in which the bacterium provided ATP and the host provided protection and nutrients. This bacterium evolved later into the mitochondrion.

Chloroplast formation: some eukaryotic cells engulfed a photosynthetic cyanobacterium which lead to the evolution of chloroplasts in algae and plants.

Are the plants, animals, and fungi a sister taxon to the protists? Why or why not?

No, they are not because protists are not a single, monophyletic group but rather an paraphyletic group. Protists include multiple lineages that do not share a single common ancestor exclusive to them and so protists are not a true clade (monophyletic group). Animals and fungi share a more recent common ancestor with chonaoflagellates which is a type part of protist.

Did complex multicellularity arise once or several times among the eukaryotes?

Complex multicellularity across several times independently among eukaryotes. These lineages included animals, plants, fungi, and red/brown algae. Because different eukaryotic groups evolved muticellularity independently, it is an example of convergent evolution.

Groups to know: Kingdom Fungi; Divisions Ascomycota & Basidiomycota.

Kingdom Fungi is eukaryotic, heterotrophic, mostly multicellular, and can reproduce sexually/asexually. They can be decomposers, mutualists, or pathogens.

Ascomycota:

• produced spores in sac-like structures called asci.

• Examples; Yeast, morels and truffles

Basidiomycota:

• produces spores on club-shaped structures called basidia.

• Examples: mushrooms, puff balls, and shelf fungi

Are fungi more closely related to plants or animals?

Fungi are more closely related to animals. They evolved from a flagellated ancestor and the lineage is part of a larger group called opisthokonts, which includes animals and their fungi relatives. In this clade, fungi are more closely related to certain single celled protists than animals. DNA sequence data indicates that fungi, animals and protist form a monophyletic group which means that they all descend from a common ancestor.

What is the nutritional mode of fungi?

Fungi are heterotrophs and so feed by absorption which grows on or near their food source and secrete hydrolytic enzymes into their surroundings. These enzymes break down complex molecules into smaller compounds which fungi then absorb into their own cells. This process is known as external digestion.

What is the role of the fungal hyphae?

Fungal hyphae are thin filaments that play a crucial role in the life and function of fungi in 2 ways:

• Structure and Growth is when hyphae form an interwoven mass called mycelium, penetrating the surface on which fungi grow. This structure maximizes the surface area for nutrient absorption.

• Nutrient Absorption: Hyphae secrete hydrolytic enzymes that decompose complex organic materials into simple compounds. These simpler compounds are then absorbed by the hyphae which makes nutrient uptake more efficient.

Do fungi reproduce sexually or asexually (this is a trick question)?

Fungi reproduce asexually and sexually.

Asexual Reproduction: This is through producing haploid spores through mitosis. These spores can then rapidly colonize new food sources.

• Penciliium is an example of this

• Yeast can reproduce asexually by cell budding or division.

Sexual Reproduction:

• Plasmogamy: fusion of cytoplasm from two parent mycelia

• Karyogamy: Fusion of nuclei to form a diploid zygote.

• Meiosis: produces genetically diverse haploid spores

What is the difference between plasmogamy and karyogamy?

Plasmogamy: the fusion of the cytoplasm from two parent mycelia which results in a heterokaryotic stage in which cells contain two or more genetically distinct nuclei. This initates the sexual reproduction process.

Karyogamy: This is the fusion of haploid nuclei from the two parent mycelia which results in a diploid nucleus which then transitions into the formation of diploid cells, meiosis, and eventually completion of spores that germinate into new mycelia.

Why are fungi important in ecosystems?

Fungi are important because they serve as:

Decomposers

• break down dead material

• secrete enzymes that decompose complex molecules into simpler ones which are later absorbed by the fungi

• This decomposition recycles essential nutrients back into the ecosystem

Mutualists

• fungi form beneficial relationships with other plants

• Mycorrhizal fungi form an association with plant roots to enhance water and nutrient absorption.

Pathogen

• some fungi are parasitic and can cause diseases in plants and animals which can influence population dynamics and ecosystem health.

What are lichens and mycorrhizae composed of?

A lichen is a symbotic association between a photosynthetic microorganism and a fungus.

• it is usually unicellular or filamentous green algae or cyanobacteria

• It is most often an ascomyete but can also be a glomeromycete or basidiomycete

• The fungus forms the bulk of the lichen’s mass and gives it shape while photosynthetic cells are embedded within the fungal hyphae.

• It can reproduce asexually

Mycorrhizae

• symbiotic associations between fungi and plant roots.

• Ectomycorrhizae:

  • form a dense sheath over the roof surface

  • Hyphae: extend into the soil and root cortex but doesn’t penetrate the root cells.

• Endomycorrhizae:

  • do not form a mantle but penetrate root cells

  • Forms arbuscules within root cortex cells which facilitates nutrient exchange.

Groups to know (know their characteristics):

• Kingdom Animalia – Metazoa vs. Eumetazoa – Bilaterians –

Deuterostomes – Chordates – Vertebrates – Amniotes – Mammals –

Monotremes – Marsupials – Eutherians/Placentals – Primates

• Bony fishes, lobe-finned fishes, amphibians

Kingdom Animalia

• Metazoa

  • all animals, including sponges

• Eumetazoa

  • animals with true tissues excluding sponges.

Bilaterians

• Animals with bilateral symmetry and three germ layers

• Deuterostomia, Lophotrochozoa, Ecdysozoa

Deuterostomes

• a major lineage of Bilaterians

• during embryonic development, the anus forms before the mouth

• Hemichordata, Echinodermata, Chordata.

Chordates

• belong to Chordata

• Notochord —> flexible rod that provides support

• dorsal hollow nerve cord —> becomes the brain and spinal cord in vertebrates.

• pharyngeal slits —> openings near the throat that can develop into gills or other structures

• post-anal tail —> A tail that extends beyond the anus

Vertebrates

• subgroup of chordates with a backbone

• includes fish, amphibians, reptiles, birds, mammals

Amniotes

• vertebrates with an amniotic egg that protects the embryo.

• includes reptiles, birds and mammals

Mammals

• Endothermic vertebrates with:

  • hair

  • mammary glands

  • three middle ear bones

  • most give birth to live young

• Subgroups:

  • Monotremes: Egg-laying mammals

  • Marsupials: Mammals with a pouch

  • Eutherians/Placenta: Mammals with a complex placenta

Primates

• includes monkeys, apes, and humans

• Characteristics:

  • grasping hands/feet

  • forward-facing eyes

  • large brains relative to body size

Bony Fishes

• Skeleton made mostly of bone (not cartilage)

• Ray-Finned Fishes: most common

• Lobe-Finned Fishes: have fleshy, muscular fins

Amphibians

• first vertebrates to ever live on land

• Dual Life: start as aquatic larvae, then metamorphose into land adults

• Moist skin for gas exchange includes frogs, toads, and salamanders.

Know where on the tree of life the following characteristics appeared:

• Notochord, vertebrae, jaws, lobed fins, limbs with digits, amniotic egg

1. Notochord - appeared in the common ancestor of all chordates which provides support

2. Vertebrae - developed in the early vertebrates which provided a backbone

3. Jaws - emerged in jawed vertebrae which allowed for more efficient predation

4. Lobed Fins - found in lobe-finned fishes, which have a robust internal bone structure

5. Limbs with Digits - evolved in tetrapods for movement on land

6. Amniotic Egg - appeared in amniotes which allowed for reproduction on land

What are the 4 shared characteristics of chordates?

Chordates

• belong to Chordata

• Notochord —> flexible rod that provides support

• dorsal hollow nerve cord —> becomes the brain and spinal cord in vertebrates.

• pharyngeal slits —> openings near the throat that can develop into gills or other structures

• post-anal tail —> A tail that extends beyond the anus

What characteristics are shared by amphibians?

Amphibians

• Dual Life Stages: many amphibians, like frogs, have a life cycle that includes both aquatic and terrestrial stages. They start as aquatic larvae and undergo metamorphosis to become terrestrial adults.

• Moist Skin: They have permeable skin that allows for gas exchange which is why they stay in moist environments to prevent dehydration

• Eggs without Shells: Their eggs are laid in water or moist environments and lack a protective shell

• External Fertilization: The male releases sperm over the eggs as the female lays them

• Diverse Habitats: some amphibians have adapted to live in relatively dry environments by burrowing or living under moist leaves

What made the amniotes so successful in the terrestrial environment?

1. Amniotic Egg: contain four specialized membranes that protect and nourish the embryo

   1. Allantois - disposal sac for certain metabolic wastes produced by the embryo

   2. Chorion - gas exchange between this and the membrane of the allantois

   3. Amnion - protects embryo in a fluid-filled cavity that cushions against mechanical shock

   4. Yolk Sac - contains the yolk which is a stockpile of nutrients, and other nutrients are stored in the albumin which is the egg white

2. Shell

   1. this shell slows dehydration and allows amniotes to occupy a wider range of land habitats than amphibians

3. Rib Cage Ventilation

   1. uses rib cage to ventilate their lungs which allows for better oxygen intake and supports higher metabolic rates

4. Less Permeable Skin

   1. this development helps conserve water which allows amniotes to thrive successfully

Who are the closest relatives of birds on the tree of life?

The closest relative of birds on the tree of life is a crocodile.

• they both belong to a group called the Archosaurs which is a clade within reptiles that includes extinct dinosaurs and pterosaurs.

• Four-Chambered Hearts: Both birds and crocodiles have this which is efficient for oxygen transport

• Vocalizations - birds sing to defend their territories and attract mates, while crocodiles produce bellowing purposes for similar reasons

• Nest building and egg care: both groups build nests and care for their eggs

Is hominid diversity on earth in the present-day typical of the past 3 million years

or unusual? In what way has hominid diversity changed?

It is unusual. Before, multiple hominid species coexisted but now only Homo sapiens remain which makes the diversity of today much less compared to before.