chapter 9,10 and 11 Flashcards

Question

4 conditions of natural selection

Answer 1

Variation- Individuals in a population vary genetically, which leads to phenotypic differences. Selection pressure-An environmental selection pressure impacts the survivability of organisms within a population and their ability to reproduce. Selective advantage-Individuals with phenotypes that are fitter or more advantageous under the environmental selection pressure are conferred a selective advantage, allowing them to survive and reproduce more successfully. Heritability-must be heritable

Answer 2

a factor in the environment (e.g. limited resources, deforestation, changing temperature, predation) that impacts an organism’s ability to survive and reproduce

Answer 3

the flow of alleles in and out of a population due to the migration or interbreeding of individuals between two populations

Answer 4

immigration- the movement into a population emigration- the movement out of a population

Answer 5

a group of individuals who are able to breed with each other and produce viable and fertile offspring. Speciation is the process by which populations genetically diverge until they become distinct species.

Answer 6

the geographic (isolation) separation of a population from a parent population resulting in the formation of a new species. (no flow) v-variation I-isolation S-selection pressure A-Selective advantage T-time A-accumalation of mutations, they cant reproduce anymore, different species have been created

Answer 7

Geographical – individuals may not be able to interact with each other due to separation by barriers (e.g. body of water) Ecological – individuals may inhabit different ecological niches or habitats so they do not interact with each other. Temporal– the time of the day or year when individuals are ready to breed may differ. Behavioural – the type of mating behaviours, such as mating call, of individuals may vary. Structural– the physical characteristics of individuals may drastically vary, physically preventing breeding

Answer 8

a group of individuals who are able to breed with each other and produce viable and fertile offspring

Answer 9

Gamete mortality– the sperm may be unable to penetrate the ovum for fertilisation. Zygote mortality – fertilisation may occur and a zygote may be formed, however, it will not survive. Hybrid sterility – a viable offspring may be formed and may survive until adulthood, but will not be fertile

Answer 10

The Galápagos Islands are a collection of 19 islands situated in the Pacific Ocean west of Ecuador. Each of the 19 islands represents a specific ecological niche, each with its own different selection pressures and species. beak shape change according to the food they consumed

Answer 11

It has been hypothesised that the formation of these different species of Galápagos finches has largely been a result of allopatric speciation. This is because each of the islands is separated by the ocean, preventing gene flow. Moreover, different islands have different food sources and each island presents its own selection pressures, selecting for different phenotypes (such as beak shape) and allowing for genetic differences to accumulate. Subsequently, once sufficient differences accumulated and viable and fertile offspring could no longer be produced through interbreeding, new species of finches were formed

Answer 12

Sympatric speciation involves the formation of a new species in populations located in the same geographical location. different selection pressure act on different phenotypes within a population. also arise from g enetic abnormalites

Answer 13

While Howea belmoreana inhabits neutral and acidic soils (low pH), Howea forsteriana inhabits a region of alkaline soil (high pH) known as calcarenite.This led researchers to suggest that Howea forsteriana diverged from its sister species Howea belmoreana after the initial population colonised the alkaline soil, which acted as a selection pressure.Flowering time acted as a isolation mechanism

Answer 14

Genetic drift involves changes to a population’s allele frequencies due to sudden and random occurrences.

Answer 15

The bottleneck effect occurs when a large portion of a population is wiped out by a random event such as a natural disaster. These events can dramatically decrease the population size, significantly impacting allele frequencies. Due to the severe reduction in population size, many individuals carrying unique alleles can be lost. Therefore, the new population has lower genetic diversity than the pre-disaster population

Answer 16

The founder effect occurs when a small unrepresentative sample of individuals separates from a larger population to colonise a new region and start a new population

Answer 17

the changing of a population’s gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait. Also known as artificial selection natural selection a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles

Answer 18

Variation, Selection pressure- Direct human intervention places an artificial selection pressure upon a population of individuals, only allowing certain individuals with desirable traits to breed together. Heritability

Answer 19

If poor breeding practices are implemented, selective breeding can cause a humaninduced genetic bottleneck. This is because in large populations, only a small percentage of individuals express traits desired by humans. Additionally, reduced genetic diversity can lead to increased inbreeding, which can increase the prevalence of deleterious alleles, and a lower adaptive potential. These two effects are detrimental to the survival of a population.

Answer 20

(1) outline that variation exists, (2) identify the presence of a new selection pressure (exposure to antibiotic), (3) identify the group that is conferred an advantage, and (4) highlight the increased heritability of the antibiotic-resistant alleles. Variation and the emergence of new alleles conferring resistance against antibiotics is facilitated largely by mutations. Through mutations, new alleles can help bacteria develop mechanisms which increase their ability to combat the action of antibiotics. Some of these mechanisms, such as the impermeability of an antibiotic due to a modified cell wall or the active efflux of an antibiotic out of a bacteria

Answer 21

antigenic drift, which involves small and gradual changes in the genes encoding for viral surface antigens antigenic shift, which involves sudden and significant changes in the genes encoding for viral surface antigens. This commonly occurs when two or more different strains of a virus combine when coinfecting the same host to form a completely new subtype through a process known as viral recombination

Answer 22

Remnants of an organism are rapidly covered by sediment, meaning that the dead organism is not exposed to oxygen, microorganisms, and other disturbances that would increase its rate of decomposition. Over time, sediment layers build upon each other and compact, layer by layer, until pressure cements them together to form sedimentary rock Within this rock, the fossilised remains can take many forms, including a permineralised , mould, or cast fossil.

Answer 23

a fossil that shows traits that are common to both its ancestral group and its descendant group. They are particularly important when the descendant species is physically very distinct from the ancestral species, such that the transitional fossil can help demonstrate evolutionary changes between the two

Answer 24

Radioisotopes are unstable elements that will break down over time into a more stable product. For instance, carbon-14 (a radioisotope) will break down into nitrogen-14. While these radioisotopes can break down at any point, on average the rate of breakdown is constant and can be modelled. One of the ways in which we model this breakdown is by calculating the half-life of that radioisotope. Half-life describes the amount of time before half of the mass of a radioisotope is broken down into predictable and stable products. For example, carbon-14 is a radioisotope that has a half-life of 5 730 years. This means that after 5 730 years of anorganism’s death, half of its carbon-14 atoms will have broken down into nitrogen-14 atoms

Answer 25

Carbon-14 – nitrogen-14, 5 730 years Uranium-235 – lead-207, 700 million years Potassium-40 – argon-40 , 1.3 billion years

Answer 26

The law of fossil succession states that because sedimentary rock is formed by the accumulation of sedimentary layers on top of each other, the fossils closer to the surface must be younger than those that are found below them . This means that we can assign fossils a relative age – an approximate age based on the position of the fossil compared to other fossils

Answer 27

atching rock layers from different locations based on similarities in their fossil content or other characteristics.

Answer 28

physically distinctive have had a large population have existed in many geographical areas only lived within a known short period of time.

Answer 29

features present in two or more species that may look and function very differently in each species, but are derived from a common ancestor Homologous structures are physical evidence of divergent evolution, the evolutionary process where two or more populations of a single species accumulate enough genetic differences to be classified as different species.

Answer 30

the process in which a common ancestor evolves into two or more descendant species

Answer 31

Analogous structures are structures that serve similar biological functions but are not derived from a common ancestor. Analogous structures are evidence of convergent evolution in which two or more distantly related species can be seen to have independently evolved similar traits to adapt to similar environments and selection pressures.

Answer 32

features that have lost all or most of their usefulness as a result of evolution by natural selection, easy method to infer relatedness between species.

Answer 33

Molecular homology is the study of the similarities between organisms at a DNA and amino acid level. There are many different types of proteins present in the body, but when studying amino acid sequence similarities, we analyse proteins from conserved genes which are found in a number of different species.

Answer 34

mtDNA is almost 17 000 nucleotides long in humans and contains 37 genes, compared to the over 24 000 genes in our nuclear DNA. The mutation rate in mtDNA is much higher than in nuclear DNA. This means that for very closely related species, the mutation rate still ensures that there are enough differences in DNA sequences for us to compare. There is no recombination (mixing of DNA between homologous chromosomes during meiosis) in mtDNA because it’s only inherited from the mother. This means that mtDNA remains unchanged from generation to generation, which makes it easier to trace past ancestors.

Answer 35

Within the order of primates, humans are further classified into the superfamily Hominoidea. Species belonging to this superfamily are called hominoids (or apes) Broader rib cage and pelvis, helping hominoids sit upright by creating a wide, stable chest Lack of tail, contributing to the hominoid’s ability to sit upright Shorter spine between the rib cage and pelvis, helping hominoids sit upright Increased cranium size as hominoid brains tend to be larger and more complex than other primates Typically longer arms than legs (except Homo sapiens), shoulder blades that sit further back, and shoulder joints that allow the arm to swing back

Answer 36

Lived in Europe/West Africa from 200 000 to 27 000 years ago. Short (males around 165 cm) and powerful, with large brow ridges and brains slightly bigger than modern humans. They were expert toolmakers and hunters who were thought to have bred with modern humans.

Answer 37

3D colour vision and forward-facing binocular eye A large cranium relative to body weight A large number of sensitive touch receptors in their fingertips Prehensile hands and feet consisting of five digits each, with one opposable digit to help them grasp objects with power and precision

Answer 38

Living between 2.3-1.6 mya in East/South Africa, members of H. habilis had 50% larger brains than the australopithecines, as well as smaller teeth and a less protruding face. H. habilis was similar to the australopithecines in that it still had long arms and shorter legs suitable for climbing

Answer 39

bipedalism Pelvis – Human pelvises are more shallow and bowl-shaped than other primates, whose pelvises tend to be vertically long and narrow. The bowl-shaped pelvis helps provide support for the upper body whilst standing and walking upright. – The human foot no longer has prehensile capabilities, and the big toe is in line with the other toes. Human feet also have two arches and a wide heel, making bipedalism more energy e cient and less impactful on the foot. The rib cage in humans is more barrel-shaped than gorillas who have funnel-shaped rib cages instead. This helps humans to maintain an upright posture for a lengthy period of time.

Answer 40

Appeared 1.8 mya in Africa, and was later found throughout much of Asia and Europe. Lived until as little as 200-300 000 years ago, and were much more human-like than anything prior – bigger brain, longer legs, shorter arms and more sophisticated tools. Homo erectus are often credited with much of the migration out of Africa.

Answer 41

Nuclear DNA studies in 2010 show around 1–4% of the human genome is identical to DNA found in Neanderthals . This 1–4% similarity was only found in the genomes of non-African populations and not in sub-Saharan African genomes. 100 000 year old DNA from Neanderthal fossils found in Siberia in 2016 contained a significant amount of ancient human DNA not found in other Neanderthal populations

Answer 42

In 2010, scientists reported the discovery of bone fragments of a new hominin species in Denisova Cave in Siberia. The bones were dated to around 40 000 years ago. Upon analysis, nuclear DNA from the bone was found to be very closely related to Neanderthals, but different enough to be a new distinct species, termed Homo denisova, or Denisovans. Due to a lack of discovered fossil evidence, most of the inferences about the Denisovans have been made purely from DNA evidence. For example, only a few small teeth were uncovered in the original Denisova Cave (Figure 6), as well as a partial jawbone discovered in the Tibetan Plateau in 2019.

Answer 43

greater genetic diversity in African populations * mtDNA traced back to common ancestor in Africa * existing fossil record, especially along the east coast of Africa and into the Middle East * cultural artefacts, such as stone tools and cave paintings