Biology Chapter: Cell Organelles and Bacteria

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are two main types of organelles that possess circular DNA?

Mitochondria and plastids.

What is one hypothesis that explains the origin of multicellularity?

The colonial hypothesis, which suggests that colonies form through the cooperation of unicellular organisms.

How can prokaryotes like bacteria influence population dynamics?

Through cellular mechanisms that affect their reproduction and survival rates.

What distinguishes Gram (+) bacteria from Gram (-) bacteria?

The structure of their cell walls; Gram (+) have a thick peptidoglycan layer, while Gram (-) have a thin layer and an outer membrane. Signup and view all the answers

What is one way bacteria can evolve antibiotic resistance?

Through mutations that confer survival advantages against antibiotics. Signup and view all the answers

Describe the concept of the 'RNA world' in the context of self-replication.

The 'RNA world' hypothesis suggests that RNA molecules were the first self-replicating entities, capable of catalyzing their own replication and serving as templates for amino acid synthesis, paving the way for evolution through natural selection. Signup and view all the answers

How do vesicles demonstrate properties of life, such as metabolism and reproduction?

Vesicles can reproduce by dividing spontaneously, perform metabolic reactions using external molecules, and grow by increasing in size, showcasing key life properties emerging from abiotic conditions. Signup and view all the answers

What role do fossils play in understanding the evolutionary relationships in the tree of life?

Fossils provide evidence of morphological and anatomical similarities that help group species together, allowing scientists to understand evolutionary relationships and how they have changed over time. Signup and view all the answers

Explain the difference between biostratigraphy and radiometric dating in determining the age of fossils.

Biostratigraphy uses the relative positions of sedimentary rock layers to estimate ages, while radiometric dating measures the decay of isotopes in magmatic rocks for precise absolute ages. Signup and view all the answers

What is faunal succession and how does it help in studying the geological record?

Faunal succession refers to the specific vertical sequence of fossilized organisms that can be consistently identified across different geographic locations, assisting in correlating ages of sedimentary layers. Signup and view all the answers

What is the role of xylem in a plant's transport system?

Xylem transports water and minerals to the leaves. Signup and view all the answers

Define heterospory and its advantages in seed plants.

Heterospory is the production of two types of spores, which enhances genetic diversity and allows separate gametophytes to nourish the embryo. Signup and view all the answers

What protective innovations do seed plants possess for their gametophytes?

Seed plants have a reduced, protected gametophyte nourished by the sporophyte, often in the form of pollen grains. Signup and view all the answers

How has the evolution of lignin contributed to plant development?

Lignin provides structural support, allowing plants to grow tall and compete for light. Signup and view all the answers

What is the significance of the ovule in seed plants?

The ovule contains the megaspore, enabling fertilization without the need for water. Signup and view all the answers

What role did xylem and phloem play in the evolution of early forests during the Devonian period?

Xylem transported water and minerals to leaves while phloem distributed sugars, enabling plants to grow taller and compete for light. Signup and view all the answers

Discuss the difference between homosporous and heterosporous plants in terms of gametophyte production.

Homosporous plants produce one type of bisexual gametophyte, while heterosporous plants produce two types of gametophytes, male and female. Signup and view all the answers

Explain how the reduction of the gametophyte benefits seed plants.

The reduced gametophyte is protected from environmental stress and directly nourished by the sporophyte, enhancing survival and reproductive success. Signup and view all the answers

What are the implications of the ovule structure for reproduction in seed plants?

The ovule allows fertilization without the need for water, facilitating reproduction in diverse environments. Signup and view all the answers

How does heterospory contribute to genetic diversity in seed plants?

Heterospory allows gametophytes to mature at different times, reducing chances of self-fertilization and increasing genetic diversity. Signup and view all the answers

Study Notes

Topic 8: The Tree of Life

Life originated 3.5 billion years ago (first direct evidence).
The universe is 13.8 billion years old.
Earth is 4.6 billion years old.
Fossils are preserved remnants or impressions of past organisms.
Stromatolites are layered rocks formed by photosynthetic prokaryotes.

Learning Outcomes

Describe seven properties of life using an organism as an example.
Justify the importance of C, H, N, and O in organic molecules.
Explain how specific life properties emerged during protocell formation.
List advantages of RNA molecules for life emergence.
Explain how fossils can reveal the evolution of organisms.
Compare fossil dating methods.
Describe the Burgess Shale's contribution to animal evolution.
Define mass extinction and give an example.
Define adaptive radiation and give an example.
Analyse graphical data to understand taxonomic changes.
List common ancestor (LUCA) characteristics.
List 3 domain characteristics.
Give examples of organisms in each domain.
Explain eukaryote evolution from endosymbiosis.
Explain the evolution of multicellularity.

7 Properties of Life

Living organisms share seven properties:
- Cellular organization
- Metabolism
- Heredity and evolution
- Growth and development
- Reproduction
- Regulation and homeostasis
- Response to stimuli
Viruses are not considered living. They lack these characteristics.

First Evidence of Life on Earth

Age of the universe: 13.8 billion years.
Age of Earth: 4.6 billion years.
First direct evidence of life: 3.5 billion years.
Fossil: preserved remnants or impressions of past organisms.
Stromatolite: layered rock formed by photosynthetic prokaryotes.

Life on Earth Uses Carbon

Carbon is highly abundant on Earth and its atmosphere.
It is a key element in most biological molecules, including:
- Carbohydrates
- Proteins
- Fatty acids
- Nucleic acids

How Did Life Originate on Earth?

Primordial "soup" (prebiotic soup): hypothetical set of conditions leading from abiotic to biotic.
Four steps leading from organic molecules to protocells:
- Abiotic synthesis of small organic molecules.
- Polymerization of small molecules into macromolecules.
- Packaging of these molecules into protocells.
- Origin of inheritance through the transmission of self-replicating molecules.

Stanley Miller's Experiment (1953)

Mimicked early Earth's atmospheric conditions.
Resulted in the synthesis of amino acids.
Similar experiments with volcanoes produced more amino acids.

Formation of Macromolecules

Polymers of amino acids and nitrogenous bases can form spontaneously without enzymes or ribosomes.
Thermal energy (heat) and catalysts (Fe²⁺, Pb²⁺, Mg²⁺, etc.) increase reaction rates.
Clay has been found to be a mineral catalyst for RNA polymerization.

Formation of Protocells

Protocells are droplets with membranes that maintain a different internal chemistry than the environment.
Experiments show protocells can divide, reproduce, exhibit internal metabolism, increase in size, have selectively permeable membranes, and respond to stimuli.

Self-Replication

RNA molecules can catalyze reactions and self-replicate (ribozymes).
Natural selection favors RNAs that replicate faster.
Inheritance occurs through RNA transfer during vesicle splitting.

Using Fossil Records

Fossils reveal relative and absolute ages of organisms that lived in the past.
Many fossils belong to extinct species.
Some fossils resemble present-day organisms.
Organisms can undergo rapid morphological changes.
Biostratigraphy: uses specific species as markers to date sedimentary rocks.
Radiometric dating: determines the absolute age of magmatic rocks.
Faunal succession: the distinct vertical order of fossils can be reliable over wide horizontal distances, used to define intervals geological layers.

The Tree of Life

The tree of life depicts the evolutionary relationships of organisms (living or extinct).
Morphology, anatomy, or genetic sequences can group species.
The tree topology is updated by new data.

Geological and Fossils Records

Biostratigraphy, the determination of relative age.
Radiometric dating, determines absolute age.
Faunal succession: sequence of fossilized flora and fauna over time.

Biostratigraphy

Species with specific survival conditions and existence time serve as markers of rock layers.
Foraminifera: unicellular aquatic eukaryotes (Cambrian 540 Mya) with widespread distribution, specific habitats, diverse morphologies, and well-preserved calcium carbonate shells.

Radiometric Dating

Radiometric dating utilizes changes in isotope composition to reveal the age.
Unstable isotopes decay at constant rates into stable daughter isotopes.
The ratio of isotopes is used to calculate the fossil's age.

But the Fossil Record is Often Incomplete

Many fossils are lost or undiscovered.
Species with hard shells and long lifespans are overrepresented.
Discontinuities are observed because of geological events, climate change, and evolutionary changes.

Mass Extinctions

Geological/paleontological eras are characterized by changes in fossil records, including mass extinctions (large numbers of species disappearing).
These events can be caused by changes in temperature, volcanic eruptions, or meteorites.
Mass extinctions lead to cascading ecological changes.
Adaptive radiations frequently follow mass extinctions and create many new families and genera (species).

Key Innovations in the Fossil Record

The record reveals key innovations, like the emergence of first cells, increasing atmospheric oxygen, endosymbiosis (eukaryotic cells' origins), sexual reproduction, multicellularity, and colonization of land.

Number of Species in the Tree

Many species have been identified and described, with many others still being discovered and some extinct.
There is a large number of estimated prokaryotes and other species waiting to be discovered.
There are ~1,410,500 described species, ~200,000 of which are marine organisms. The exact number of prokaryotic species is still unknown.

Last Universal Common Ancestor (LUCA)

All living organisms utilize L-amino acids and a near-universal genetic code.
LUCA existed earlier than the first living organism.
LUCA analyzed in 2006 had approximately 355 genes.
It is likely LUCA lived near deep-sea vents in an oxygen-poor environment (anaerobic) and could use CO2 and H2.

The Tree of Life – 3 Domains System

The tree of life groups organisms into three domains: Bacteria, Archaea, and Eukarya.
Based on their evolutionary ancestry, their distinguishing characteristics and traits.
Examples of organisms from each domain: -Bacteria: -Archaea: -Eukarya:

Domain Bacteria

Approximately 700,000 estimated species (10,000 described).
Showing diverse metabolism, with photoautotrophs, aerobes, anaerobes, and those that can use O2, SO4⁻², NO₃⁻, NH₃, H₂S.
Commonly resistant to harsh conditions.

Domain Archaea

About 50,000 estimated species (500 described).
Extremophiles: living in extreme conditions such as high salinity, hot, and acidic environments.
Many are methanogens, producing methane using CO2 and H2.

Domain Eukarya

Approximately 11,000,000 species estimated (1,400,000 described).
Evolved from prokaryotes, including a cytoskeleton, endomembrane system and a nucleus.
Endosymbiotic origin of mitochondria and plastids.

Multicellularity (1,200 Mya)

Colonial hypothesis: colonies form through the cooperation of unicellular organisms.
Symbioisis hypothesis: cells from different species form a mutually beneficial association.
Many unicellular eukaryotes evolved into multicellular forms in a separate event, at least 25 times.

Topic 9: Bacteria and Archaea

Prokaryotic classification
Prokaryotic characteristics
Prokaryotic reproduction
Prokaryotic evolution
Prokaryotic genetics
Importance of prokaryotes in the ecosystem
Prokaryotic cellular mechanisms that impact the populations
Antibiotic-resistance mechanisms in prokaryotes.
Genetic recombination in prokaryotes: conjugation, transduction, and transformation.

Topic 10: Eukaryotes

Eukaryotic classification
Eukaryotic characteristics
Eukaryotic reproduction
Eukaryotic evolution
Eukaryotic genetics
Importance of eukaryotes in the ecosystem
Eukaryotic cellular mechanisms that impact the populations
Specific diseases associated with eukaryotes infections

Topic 11: The Evolution of Plants

Plant groups
Plant phylogeny
Plant reproductive innovations
Problems of plant life on land
Plant adaptations for land

Topic 12: The Evolution of Animals I

Animal classifications and characteristics
Animal phylogeny
Reproduction in animals
Animal development
Animal physiology

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the various types of organelles, their DNA structures, and the unique characteristics of prokaryotes such as bacteria. Explore concepts like the origin of multicellularity, population dynamics, and antibiotic resistance in this insightful quiz.