Biology final🤞🏽

What is scientific methodology

A process used to establish facts through objective testing and experimentation. It involves:

1. Asking a question

2. Forming a hypothesis

3. Making a prediction

4. Designing and running an experiment

5. Analyzing the results

6. Using results to create new hypotheses.

Are cytoskeleton present in prokaryotes

Prokaryotes lack well-developed cytoskeletons, which limits the extent to which they can be asymmetric and change shape over time

What domain do protists belong to

Eukarya, they used to have their own Protista clade

What are the types of eukaryotes

Plants, fungi, animals and protists

Which eukaryote exhibit more structural and functional diversity

Protists

What are the organelles used by protists

• nucleus

• endoplamic reticulum

• golgi apparatus

• lysomes.

• organelles not found in other eukaryotes, like contractile vacuole (pump excess water from cell)

What are some experimental designs

Koch’s postulates, field and lab work

What is the function of cytoskeleton in eukaryotic cells

Provides structural support that allows eukaryotic cells to be asymmetric as well as changing their shape as they move, grow and feed

Which crisis is worse than threats from climate change

the biodiversity crisis

How many species are directly threatened by extinction

over 37,000 species. 1 in 4 species

What are the top 3 species most threatened by extinction

amphibians, conifers and sharks and rays

What are key threats to biological systems

Habitat Destruction, Invasive Species, Population, Pollution, and Over-harvesting & Bycatch. (HIPPO acronym)

What is the Hadean Eon known for?

• Formation of Earth

• Early crust formed from cooling magma.

• Intense heat and heavy bombardment from space.

• Moon formation: Likely from a giant impact.

• Differentiation of Earth’s layers: Formation of core, mantle, and crust.

• Possible RNA synthesis and replication: Early molecules forming life’s building blocks.

• Folding of active ribozymes: RNA molecules with enzymatic functions.

When did Earth form?

Approximately 4.6 billion years ago.

How did the Moon form?

From coalesced debris after a large object collided with Earth.

What was Earth’s early atmosphere composed of?

Initially hydrogen and helium (lost quickly), followed by volcanic outgassing producing water vapor, CO₂, CH₄, and N₂.

When did liquid water first appear?

Toward the end of the Hadean, despite high surface temperatures, due to high atmospheric pressure.

What is abiogenesis?

The process by which life arose from non-living matter, not fully understood and thought to involve multiple stages.

What are the proposed stages of abiogenesis?

Formation of small organic molecules, assembly into larger polymers, self-replicating RNA/molecules, and LUCA (Last Universal Common Ancestor).

What is LUCA?

Last Universal Common Ancestor of all current life on Earth a protocell

What defines the Archaean Eon?

• First evidence of life and rock formation.

• Prokaryotic dominance (single-celled organisms).

• Mostly water-covered planet with high volcanic activity.

• High heat flow (3-2 times greater than today).

• Formation of early Earth’s crust and small proto-continents from magma flow.

• Weak Earth’s magnetic field.

When did the first signs of life appear?

3.7 billion years ago, from biogenic graphite in rocks.

What are stromatolites?

Layered structures formed by cyanobacteria, first identifiable fossils from 3.5 billion years ago.

What triggered the Great Oxygenation Event?

Photosynthesis by cyanobacteria releasing oxygen into oceans, which reacted with iron to form banded iron formations.

When did the Great Oxygenation Event occur

in the early Proterozoic Eon, approximately 2.4 billion years ago.

When did oxygen begin accumulating in the atmosphere?

Around 2.7 billion years ago.

What happened around 2.5 billion years ago?

O₂ levels reached about 1–10% of today’s levels, ending the Archaean Eon.

What characterizes the Proterozoic Eon?

• Atmospheric oxygen rise (Great Oxygenation Event).

• Ozone layer formation protecting life from UV radiation.

• Rise of eukaryotic cells (more complex cells).

• Endosymbiosis: Symbiotic relationship leading to mitochondria and chloroplasts in eukaryotes.

• Multicellularity: Emergence of multi-celled organisms.

• First glaciation: Evidence of global ice ages.

What caused the first major glaciation (Snowball Earth)?

The rise in atmospheric O₂ during the Great Oxidation Event reduced methane levels, weakening the greenhouse effect and triggering global cooling around 2.4–2.1 billion years ago.

When did eukaryotic cells arise?

About 2 billion years ago through endosymbiosis.

When did the first multicellular organisms appear?

Around 1.3 billion years ago.

When was the earliest eukariotic fossil

1.8 billion years ago

What are the Ediacaran biota?

Soft-bodied, multicellular organisms from ~575 million years ago, some of the earliest complex life forms.

What ended the Proterozoic Eon?

• Environmental changes

• rising oxygen levels

• increased nutrients

• and biological competition led to the extinction of Ediacaran biota, marking the transition into the Phanerozoic Eon.

What are the three eras of the Phanerozoic Eon?

Paleozoic, Mesozoic, and Cenozoic.

What is the Paleozoic Era known for?

Diversification of marine life, colonization of land, and evolution of fish, amphibians, reptiles, and plants.

What is the Cambrian Explosion?

A rapid diversification of life forms around 541 million years ago, establishing most major animal phyla.

When did plants and arthropods colonize land?

Around 500 million years ago.

When did vertebrates move onto land?

During the Devonian (~419–359 Ma).

What challenges did early land organisms face?

• Desiccation

• UV exposure

• gas exchange

• structural support

• reproduction.

What caused the end of the Paleozoic?

Formation of Pangaea, volcanic activity (Siberian Traps), climate change, acid rain, and ocean acidification.

What are the aftermath of the Paleozoic era collapsing

collapse of ecosystems due to multiple enviromettal stressors, severely depopulated earth, survivors dominate mesozoic era

What are the four eons in order from oldest to most recent?

Hadean, Archaean, Proterozoic, Phanerozoic.

What are the six periods of the Paleozoic Era in order?

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian.

What are the three periods of the Mesozoic Era in order?

Triassic, Jurassic, Cretaceous.

What are the three periods of the Cenozoic Era in order?

Paleogene, Neogene, Quaternary.

What defines the Cambrian Period?

• Cambrian Explosion: Rapid diversification of life.

• Appearance of most major animal phyla.

• Hard body parts (e.g., shells, exoskeletons).

• Emergence of bilateral symmetry and complex body plans.

What defines the Ordovician Period?

Rise of jawless fish and coral reefs; first primitive land plants; marine biodiversity flourished.

What defines the Silurian Period?

First jawed fish, first vascular plants, and first terrestrial arthropods like scorpions and insects appeared.

What defines the Devonian Period?

Known as the Age of Fishes; first forests, seed-bearing plants, tetrapods, and flying insects emerged.

What defines the Carboniferous Period?

Lush vegetation and extensive coal swamps; amphibians thrived; first reptiles evolved.

What defines the Permian Period?

Formation of Pangaea; reptiles diversified; ended with the largest mass extinction in Earth's history due to volcanic activity and climate change.

What defines the Triassic Period?

Recovery from the Permian extinction; first dinosaurs and mammals appeared; Pangaea began to break apart.

What defines the Jurassic Period?

Dinosaurs dominated land; first birds appeared; lush plant growth supported diverse ecosystems; marine reptiles thrived.

What defines the Cretaceous Period?

Flowering plants (angiosperms) evolved; peak dinosaur diversity; ended with the asteroid impact that caused mass extinction.

What defines the Paleogene Period?

Rapid diversification of mammals and birds; development of modern plant and insect relationships; cooler climate began.

What defines the Neogene Period?

Emergence of modern mammal and bird families; expansion of grasslands; appearance of early human ancestors (hominins).

What defines the Quaternary Period?

Characterized by Ice Ages; rise of Homo sapiens; development of agriculture and complex civilizations.

What defines the Mesozoic Era?

Age of reptiles, dinosaurs, marine reptiles, early birds and mammals, and breakup of Pangaea.

What groups dominated the Mesozoic?

Dinosaurs, marine reptiles, early mammals, gymnosperms, and later angiosperms.

What ended the Mesozoic Era?

A massive meteor impact leading to mass extinction, including non-avian dinosaurs.

What characterizes the Cenozoic Era?

Age of mammals and birds, diversification after the dinosaur extinction.

What does evolutionary theory explain

explains how life changed after its origin, not the origin of life itself.

What is abiogenesis

process that gave rise to life on earth

What does the prevailing scientific hypothesis suggests

the transition from nonliving to living matter was not a single event. It involved:

1. A habitable Earth with a reducing atmosphere (lacking oxygen).

2. Prebiotic synthesis of small organic molecules (e.g., amino acids).

3. Molecular self-replication (the ability of molecules like RNA to replicate themselves).

4. Self-assembly of molecules into more complex structures, leading to the first forms of life.T

Does evolution favour organisms always getting better

no, reproductive fitness is linked to the environment, not progress

What is the role of natural selection

eliminates individuals less reproductively fit in a particular environment.

What is the oldest fossil

stromatolites 3.5 billion years ago

What is the ultimate source of genetic variations

random mutations

Does natural selection involve organisms trying to adapt

no, this is Lamark’s view

Lamarck's view

"Inheritance of acquired characteristics" and "Use and disuse".

What does "Use & Disuse" contradicts

vegistual structure

What are vestigial structures

traits that no longer provide a functional advantage.

What is the difference between use and disuse theory and vegistual structures

Use & Disuse Theory:

• Organisms quickly change based on immediate needs (traits are enhanced or diminished depending on use).

Vestigial Structures:

• Body parts that were once useful but are now useless due to long-term evolution (e.g., appendix in humans).

Why was Lamark’s "Inheritance of acquired characteristics" theory rejected

traits are passed to next generation through genes not through acquires characteristics

Does natural selection give organisms what they need

no, it has no senses on what organisms need

Why is genetic diversity important in populations

If a population has genetic variation allowing some individuals to survive a particular stress, those individuals will have more offspring, and the population will evolve.

What happens if no genetic variation is present in a population

natural selection has noting to “select” on

What is a theory in science

explanation of some aspect of the natural world well-substantiated by multiple lines of independent evidence

What are the central premise of evolutionary theory

Life has existed for billions of years and has changed over time via descent through modification by natural selection.

What can specied adaptation lead to

Species adaptation can lead to reproductive isolation and new species

What was darwin’s proposal

• Better-suited traits help individuals survive and have more offspring.

• These traits are passed down, becoming more common in future generations. (natural selection)

• Species either adapt or go extinct.

• Over time, adaptations can lead to reproductive isolation, forming new species.

What are some lines of evidence of natural selection

direct observation, hoology and vistigial structures, fossil records, biogeography

What are homologous structures

similar physical features in species that share a common ancestor

What are analogous structures

features of species that are similar in function but not in structures; not derived from same ancestor

What are transitional species

organisms that has mix traits of ancestors and descendents - middle ground

What is biogeography

distribution of species/ ecosystems in geographic space and through geological time

What makes evolution possible

genetic variations

What are the types of mutations

neutral, deleterious, lethal and advantageous

What are sources of new genetic variations

• Mutations in germ lines: Creates new alleles.

• Gene flow: Transfer of genes between populations.

• Meiosis (recombination/crossing over in prophase I): Exchange of genetic material between homologous chromosomes.

• Meiosis (independent assortment in metaphase I & anaphase I): Random distribution of chromosomes.

• Fertilization: Combines genetic material from two parents.

What is heterozygosity

2pq, measure of population variation/diversity at a single locus

How is genotypic frequencies in a population calculated

p2+2pq+q2

What are mechanisms that alter allele frequency

mutation, gene flow, Genetic drift, Natural selection, nonrandom mating/inbreeding

What is needed to assess population heterozygosity

average heterozygosity over many loci

What does Hardy-Weinberg assume

there would be no evolution if there is no mutation, no immigration, large population size, genotypes equal fitness, random mating

What is the only mechanism that consistently causes adaptive evolution

natural selection

What is Evolution by natural selection

a blend of chance (creating new genetic variations) and sorting (natural selection favoring some alleles/traits over others).

How does natural selection lead to adaptive evolution

Natural selection increases allele frequencies that enhance reproduction or survival, leading to adaptive evolution.

How does natural selection increase allele frequency

Natural selection can increase these frequencies through directional selection, stabilizing selection, or disruptive selection.

What does genetic drift in small population lead to

reduction in genetic diversity and an increased risk of harmful traits due to allele fixation