IB Biology THEME A

What is the significance of water as the medium for life?

Water facilitates chemical reactions, allows dissolved molecules to move and collide, and serves as the environment where the first cells evolved.

What is the genetic material of all living organisms?

Deoxyribonucleic acid (DNA) serves as the genetic material of all living organisms.

Why is the genetic code considered universal?

The genetic code is universal because it applies to all forms of life, as DNA carries the genetic code in living organisms.

Where is DNA mainly found in eukaryotic cells?

DNA is mainly found in the nucleus of eukaryotic cells, where it forms chromosomes.

Besides the nucleus, where else can DNA be found in eukaryotic cells?

DNA is also found in chloroplasts and mitochondria of eukaryotic cells.

What is the main component of ribosomes?

Ribonucleic acid (RNA) is the main component of ribosomes.

What role does RNA play in protein synthesis?

RNA plays an important role in protein synthesis by carrying genetic information from DNA to ribosomes.

Why are viruses not considered living organisms?

Viruses are not considered living organisms because they are unable to replicate by themselves and lack a cellular structure.

What are the three components of a nucleotide?

A nucleotide is formed from a pentose sugar, a nitrogen-containing organic base, and a phosphate group.

What are the four nitrogenous bases found in DNA?

Adenine, Thymine, Guanine, Cytosine

How does RNA differ from DNA in terms of nitrogenous bases?

RNA shares the same nitrogenous bases as DNA except for thymine (T), which is replaced by uracil (U) in RNA.

What are the two categories into which nitrogenous bases can be grouped?

Nitrogenous bases can be grouped as either purine bases (adenine and guanine) or pyrimidine bases (cytosine, thymine, and uracil).

How does the length of RNA molecules compare to DNA molecules?

RNA molecules are relatively short compared to DNA molecules.

What is the pentose sugar found in RNA nucleotides?

Ribose is the pentose sugar found in RNA nucleotides.

What are the four nitrogenous bases found in RNA?

adenine, cytosine, guanine, uracil (A, C, G, U)

What are the three main types of RNA found in cells, and what are their functions?

The three main types of RNA found in cells are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). mRNA carries genetic information from the nucleus to the ribosomes for protein synthesis, tRNA transports amino acids to the ribosomes during protein synthesis, and rRNA forms part of ribosomes.

What is the role of uracil in RNA?

Uracil replaces thymine in RNA and serves as one of the four nitrogenous bases, pairing with adenine during RNA synthesis and protein synthesis.

Where is messenger RNA (mRNA) formed, and where does it function?

Messenger RNA (mRNA) is formed in the nucleus and is then transported to the ribosomes in the cytoplasm, where it functions in protein synthesis.

What is the function of transfer RNA (tRNA) during protein synthesis?

Transfer RNA (tRNA) is responsible for transporting amino acids to ribosomes during protein synthesis, where they are incorporated into the growing polypeptide chain.

What is evolution?

Evolution is the process of changes in the heritable characteristics of organisms over generations.

What are heritable characteristics?

Heritable characteristics are traits that can be inherited by, or passed on to, the next generation.

How are heritable characteristics determined?

Heritable characteristics are determined by the alleles of genes present in an individual.

What is natural selection?

The process by which heritable characteristics that provide an advantage for survival and reproduction become more common in a population over time.

How does natural selection lead to evolution?

It favors individuals with advantageous traits, which are then passed on to offspring, resulting in gradual changes in a species over time.

What is speciation?

Speciation is the process by which new species arise from existing species, often through the accumulation of genetic changes over time.

Who proposed the theory of evolution by natural selection?

Charles Darwin proposed the theory of evolution by natural selection.

What are the key components of Darwin's theory of evolution by natural selection?

Variation within a population, competition for survival, differential reproductive success based on advantageous traits, and the gradual accumulation of advantageous traits in a population over generations.

Who developed the theory of Lamarckian evolution?

The theory of Lamarckian evolution was developed by French scientist Jean-Baptiste Lamarck in the early 19th century.

What is the main idea behind Lamarck's theory of evolution?

Lamarck proposed that changes acquired by an organism during its lifetime can be inherited by offspring, leading to evolutionary change.

What are acquired characteristics according to Lamarck?

Acquired characteristics are traits that an organism develops during its lifetime as a result of its actions or behavior.

What is the theory of evolution by natural selection?

The theory of evolution by natural selection proposes that heritable traits that provide advantages for survival and reproduction become more common in a population over time.

What are homologous structures?

Homologous structures are body parts that may look and function very differently but share structural similarities, indicating a common evolutionary origin.

Can you provide an example of homologous structures?

The limbs of animals, which have different functions but share a basic arrangement of bones.

What is adaptive radiation?

The process by which organisms with homologous structures evolve from a shared, common ancestor and adapt to different environments, leading to the diversification of species.

What is a pentadactyl limb?

A limb with five digits, such as five fingers or toes, and is present in many species across different groups of organisms.

What groups of organisms have pentadactyl limbs?

Pentadactyl limbs are present in mammals, birds, amphibians, and reptiles.

How do pentadactyl limbs in different species demonstrate homology?

Pentadactyl limbs in different species have a similar bone structure, despite enabling animals to move in different ways, indicating a common evolutionary origin.

Despite differences in function, what remains similar among pentadactyl limbs?

Among pentadactyl limbs, the layout of bones remains almost exactly the same, indicating a shared evolutionary history.

What are analogous structures?

Analogous structures are characteristics with similar form and function, but with different evolutionary origins.

What confusion do analogous structures historically cause in taxonomy?

Analogous structures can cause confusion in taxonomy because they may lead scientists to group organisms together based on similar traits, even if they do not share a close evolutionary relationship.

What is convergent evolution?

Convergent evolution is the independent evolution of similar characteristics in distantly related species, usually due to similar selection pressures in their environments.

How do analogous structures relate to convergent evolution?

Analogous structures arise as a result of convergent evolution, where similar traits evolve separately in different species due to similar environmental pressures.

What does convergent evolution suggest about advantageous characteristics?

Convergent evolution suggests that advantageous characteristics can evolve separately in different species, rather than originating from a single mutation.

Can you provide an example of convergent evolution in aquatic animals?

Dolphins and sharks are both groups of aquatic animals with a similar body shape for efficient swimming, but they belong to different classes (mammals and fish, respectively), showing convergent evolution.

How do dolphins and sharks demonstrate convergent evolution?

Dolphins and sharks have independently evolved streamlined body shapes for efficient swimming, despite belonging to different classes, showcasing convergent evolution.

What is another example of convergent evolution in plants?

Cacti and euphorbia

How do cacti and euphorbia exemplify convergent evolution?

Cacti and euphorbia have independently evolved similar adaptations to desert environments, including spiny leaves and succulent stems, despite belonging to different plant orders.

What is speciation?

Speciation is the process by which new species evolve from pre-existing species over time.

How does speciation contribute to diversity?

Speciation increases the diversity of species on Earth by generating new species from ancestral populations.

How does the theory of evolution relate to speciation?

The theory of evolution states that species change over time, leading to the process of speciation, which contributes to the diversity of life on Earth.

What is reproductive isolation, and why is it important in speciation?

Reproductive isolation occurs when two populations of a species can no longer interbreed to produce fertile offspring. It is essential for speciation because it marks the point at which two populations become distinct species.

How does gene flow relate to speciation?

When gene flow stops between two groups, speciation occurs.

What role do selection pressures play in speciation?

Different selection pressures acting on separated populations can accelerate the accumulation of genetic differences, leading to speciation.

How does extinction impact species diversity?

Extinction reduces species diversity by causing the permanent loss of species from the Earth's biodiversity.

Can you provide examples of extinct species?

Examples of extinct species include the passenger pigeon and the woolly mammoth, which no longer exist today.

Why is reproductive isolation necessary for speciation to occur?

Reproductive isolation ensures that genetic differences between populations cannot be mixed through interbreeding, allowing each population to evolve independently and eventually become separate species.

What distinguishes speciation from gradual evolutionary change?

Speciation requires the development of reproductive isolation between populations, marking the formation of distinct species

What is reproductive isolation?

Reproductive isolation occurs when changes in alleles and phenotypes prevent individuals of a species from successfully breeding with others who lack these changes, leading to the inability to produce fertile offspring.

What are some examples of changes that can lead to reproductive isolation?

Examples include seasonal changes, such as different mating or flowering seasons, and behavioral changes, such as alterations in courtship behaviors.

How does geographical isolation contribute to reproductive isolation?

Geographical isolation occurs when populations of a species are separated by physical barriers, preventing gene exchange and leading to reproductive isolation between the populations.

What are examples of geographical barriers?

Mountains, sea, rivers etc.

What is differential selection?

Differential selection occurs when different selection pressures act on isolated populations, leading to divergent evolutionary paths and potentially resulting in reproductive isolation between the populations.

How does differential selection contribute to speciation?

Differential selection can lead to differences between isolated populations, eventually resulting in reproductive isolation and the formation of distinct species through the process of speciation.

Can you provide an example of speciation resulting from geographical isolation?

An example is the speciation event that led to the evolution of bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), which occurred when populations became geographically isolated by the Congo River.

What are some differences between chimpanzees and bonobos?

Chimpanzees tend to exhibit more aggressive behaviors and have male-dominated social structures, while bonobos have more peaceful social structures with dominant females.

How do the differences between chimpanzees and bonobos illustrate differential selection?

The differences between chimpanzees and bonobos, such as their social behaviors, likely arose due to different selection pressures acting on isolated populations, leading to divergent evolutionary paths.

What is the outcome of reproductive isolation between two populations?

Reproductive isolation ultimately leads to the two populations becoming separate species, unable to interbreed and produce fertile offspring.

What is biodiversity?

Biodiversity refers to the variety of life that exists in a specified area, encompassing ecosystems, species, and genetic diversity.

Why is biodiversity important for ecosystems?

Biodiversity is crucial for the resilience of ecosystems; higher biodiversity leads to greater stability and resistance to environmental changes.

What are the three levels at which biodiversity can be studied?

Biodiversity can be studied at the levels of ecosystem diversity, species diversity, and genetic diversity.

What is ecosystem diversity?

Ecosystem diversity refers to the range of different ecosystems or habitats within a particular area, indicating the variety of environmental conditions and niches available.

How does ecosystem diversity contribute to biodiversity?

Areas with a wide variety of habitats have high biodiversity, while areas with limited habitat types have low biodiversity.

How is species diversity measured?

Species diversity can be measured by species richness (the number of species within an ecosystem) and species evenness (the distribution of individuals among species).

What is the significance of species evenness in measuring biodiversity?

High species diversity requires both high species richness and high species evenness, ensuring a balanced distribution of individuals among species.

Why are ecosystems with high species diversity more stable?

Ecosystems with high species diversity are more stable because they can better withstand environmental changes and disturbances due to the presence of multiple species performing similar functions.

Can you provide an example of the importance of species diversity for ecosystem stability?

In pine forests of Florida, where only one or two tree species dominate, a pathogen targeting one of these species could lead to the collapse of the entire ecosystem due to low species diversity.

What is genetic diversity?

Genetic diversity refers to the variety of different alleles of genes present within a species or a local population.

What factors contribute to genetic diversity?

Factors include the proportion of genes with multiple alleles and the number of different alleles present for each gene.

How can genetic differences arise between populations of the same species?

Genetic differences between populations may result from different selection pressures in distinct habitats, leading to variations in allele frequencies.

Why is genetic diversity important for a species?

Genetic diversity is crucial for a species' ability to adapt to environmental changes and survive, as it provides the raw material for natural selection to act upon.

How does biodiversity change over time?

Biodiversity changes over time due to processes like speciation, extinction, and adaptation, resulting in fluctuations in the number of species on Earth.

What does the fossil record reveal about species diversity?

The fossil record shows that many species that existed in the past are now extinct, but the number of species on Earth has generally increased over time due to periods of speciation.

What influences the accuracy of estimating the number of species on Earth?

The accuracy of estimates depends on the process of classification, as misclassification can either underestimate or overestimate the number of species.

What are lumpers and splitters in taxonomy?

Lumpers focus on similarities and are more likely to classify species together, while splitters focus on differences and are more likely to classify species separately.

How does subjectivity affect species classification?

Classification can be subjective, as determining whether organisms are of the same species or separate species can be challenging and may vary among taxonomists.

What is an ecosystem?

An ecosystem refers to all living organisms in an area and their interactions with each other and the non-living environment.

What are some human activities responsible for damaging ecosystems?

Human activities such as deforestation, habitat destruction, and clear-cutting contribute to the damage and destruction of ecosystems worldwide.

What is clear-cutting, and how does it impact ecosystems?

Clear-cutting is a practice where all trees in an area are cut down and removed, often to provide timber or clear land for agriculture, leading to significant ecosystem disruption and loss.

Can you provide a case study of anthropogenic ecosystem loss in Southeast Asia?

One example is the gradual loss of mixed dipterocarp forests in Southeast Asia, where deforestation and habitat destruction are threatening this crucial rainforest ecosystem due to practices like clear-cutting for agriculture.

How does the destruction of mixed dipterocarp forests affect the ecosystem?

The destruction of these forests disrupts biodiversity, alters local climates, and contributes to habitat loss for numerous plant and animal species that depend on them for survival.

What factors should be considered when choosing a second case study of anthropogenic ecosystem loss?

Consider choosing an ecosystem from a local or familiar region that has experienced loss due to human activities, ensuring the case study provides sufficient detail, similar to the examples provided.

Can you name examples of ecosystems from different parts of the world experiencing loss due to human activities?

Examples include the Great Barrier Reef in Australia, the Northern Great Plains in North America, and mangrove forests in various locations globally.

How does human activity contribute to the loss of the Great Barrier Reef?

Human activities such as pollution, overfishing, and climate change contribute to the degradation of the Great Barrier Reef, leading to coral bleaching and loss of biodiversity.

What are some consequences of ecosystem loss for both local and global environments?

Consequences include loss of biodiversity, disruption of ecosystem services, and impacts on local communities' livelihoods and global climate patterns.

What is the evidence required to understand the biodiversity crisis?

Solid evidence on changing biodiversity requires data from reliable sources, including surveys conducted in various habitats, repeat survey data over time, assessment of both species richness and evenness, and expert analysis.

What is in situ conservation?

In situ conservation refers to the conservation of species within their natural habitats, utilizing various strategies to protect and manage these habitats.

What are national parks?

National parks are government-controlled areas within countries where wildlife and the environment are protected. They are significant for conservation efforts and often have strict regulations to preserve their natural state.

What are nature reserves, and how do they differ from national parks?

Nature reserves are smaller regions than national parks and can be on privately or publicly owned land. While they serve similar conservation purposes, nature reserves may have different management approaches and regulations.

What are the restrictions typically imposed within protected areas?

Restrictions within protected areas may include strict control over human access, tight regulations on industrial activities like agriculture and building, and limitations or complete prohibition of hunting.

What is rewilding?

Rewilding is the restoration of ecosystems to a point where they can sustain themselves, often resulting in biodiverse habitats. It can be active or passive and may involve human intervention or allowing natural processes to restore ecosystems.