Topic 4: Evolution Flashcards
Beyblade Burst Evolution
What came first, the chicken or the egg?
The egg, dummy. If you really want an explanation come see me after class.
What were likely the first cells on Earth?
Prokaryotes living in the ocean that did not require oxygen, as the atmosphere likely contained no oxygen, but rather large amounts of carbon dioxide and nitrogen
What likely resulted in an increase in oxygen in the atmosphere?
After the first prokaryotes, photosynthetic prokaryotes became prominent and produced oxygen, releasing it into the atmosphere, making it possible for some cells to use oxygen as part of their metabolism and thus becoming more complex
What type of cell likely came first? Provide evidence
Prokaryotic cells are fundamentally simpler in their metabolism and structure than eukaryotic cells. They likely came first, as eukaryotic cells would not have been able to survive the early hostile conditions
Stromatolites are some of the oldest fossils, made up of bacteria (prokaryotes) and sediment which formed rocks
What is the proposed theory on how the first eukaryotic cells were formed?
It is proposed that the first eukaryotic cells were formed when larger prokaryotic cells engulfed some smaller ones in a process similar to phagocytosis
In some cases, the smaller cell was able to respire aerobically or could photosynthesise, allowing the newly formed ‘super cell’ to carry out more functions than either cell could do on their own
What do the terms symbiosis and endosymbiosis refer to?
The term symbiosis is used to describe the situation in which two organisms help one another and both benefit.
In the case of endosymbiosis one cell lives in another and both benefit
It is thought that what organelles are descendants of ancient bacterial cells, and what evidence supports this?
Mitochondria and chloroplasts.
They have their own circular and unbound DNA with no introns, similar to prokaryotic DNA.
They have their own ribosomes that are similar in size and rRNA sequence to bacterial ribosomes.
They are able to self-replicate independently of the cells, similar to binary fission of prokaryotes.
They have two membranes, the outer is similar to the host cell’s outer membrane and was likely formed in the same way vesicles are formed during endocytosis, and the inner is similar to the outer membrane of bacteria.
Evidence suggests that organic molecules were first formed when?
When the Earth’s condition was still hostile.
Some of these organic molecules were fatty acids that likely formed simple membranes in the form of primitive vesicles
What molecules did the first cells likely use to store and transmit genetic information?
RNA, as it is a simpler molecule than DNA, so it is likely that it was formed first
It has also been discovered that some RNA can catalyse chemical reactions under certain circumstances, these are known as ribozymes
What evidence suggests that all cells descend from an original ancestor (LUCA)?
All cells have:
A cell membrane
Nucleic acids (DNA and RNA)
Proteins - made of the same 20 amino acids and are synthesised in the same way
Water - made up of 50-80% water
Define a population and community
A group of organisms of the same species living in the same area at the same time
A community consists of several populations
What does the biological species concept define a species as?
A group of sexually reproducing organisms which can actually or potentially interbreed to produce fertile offspring
What is a hybrid?
An offspring formed by animals of different species
What are other criteria used to define a species?
Morphological similarity - similarities in shape and anatomy.
Biochemical similarity - similarities in the chemical composition of cells and tissues, including metabolic processes.
Common gene pool - similarities in genetic composition (nucleotide sequences) of the genome.
What is the most accurate method of classifying species?
Comparing DNA and amino acid sequences
What are the pre-zygotic barriers that isolate species?
Temporal isolation - Species may produce gametes at different times (time of day/season).
Behavioural isolation - Species may have different mating recognition behaviours that do not interest each other.
Mechanical isolation - Species may have anatomical differences in their genitals, so the transfer of gametes from male to female cannot take place.
Gamete isolation - Species may have sperm and ovum that have incompatible cell membrane receptors and so cannot form a zygote.
Ecological/habitat isolation - When species occupy different habitats.
What are the post-zygotic barriers that isolate species?
Hybrid inviability - Offspring fail to reach maturity by dying before or just after birth.
Hybrid sterility - Hybrid offspring remain healthy and viable but are sterile
What is reproductive isolation?
A mechanism that prevents gene flow between populations OF DIFFERENT SPECIES
Includes pre-zygotic and post-zygotic barriers
What is a mutation? How can they occur?
A permanent change in the sequence of a DNA molecule and is the ultimate source of genetic variation in a species.
They can occur spontaneously or be induced
What is an example of a spontaneous mutation, and what can induce mutations?
Copying errors when DNA is replicated.
Environmental factors such as high energy radiation (X-ray, UV), mutagenic chemicals, and viruses can induce mutations
What happens when mutations occur in germ cells?
They can be passed on to the next generations, accumulating
This results in genetic variation in organisms
What is the only source of genetic variation in asexually (Involves mitosis) reproducing organisms?
Mutation
Where can genetic variation arise from in sexually reproducing organisms?
Mutations, crossing over and independent assortment in meiosis, and the random fertilisation of gametes
