prac qs/model answers Flashcards
(dynamic) Equilibrium
refers to a state of balance or stability within a biological system where opposing processes occur at equal rates, resulting in a relatively constant overall condition over time. (eg intake of oxygen and output of carbon dioxide remain in relative equilibrium)
carrying capacity
Carrying capacity can be defined as a species’ average population size in a particular habitat. The species population size is limited by environmental factors like adequate food, shelter, water, and mates.
ecological niche
the role of a species in an ecosystem: the set of resources it consumes and habitats it occupies, as well as its interactions with other species. ecological niches exert selection pressures that push the populations in various directions.
Outline two reasons why the cane toad has
successfully invaded many areas of Australia.
- The cane toad produces toxins that deter potential predators and native species that haven’t co-evolved defences. This reduced predation allows cane toads to rapidly invade broader areas of Australia.
- A single female cane toad can lay thousands of eggs at once, and their tadpoles develop quickly in Australia’s warm, humid conditions. This speedy growth allows them to mature rapidly, generating multiple generations in a short span. This accelerated reproductive cycle aids their colonization of new habitats and establishment of self-sustaining populations before local predators or rivals can adjust to their arrival.
When were cane toads introduced into Australia?
Cane toads were introduced into Australia in June 193 5 by
Mr RW Mungromery of the Sugar Experiment Station at Meringa, Queensland.
Why were cane toads introduced into Australia?
Cane toads were introduced into Australia to control insect pests that were threatening the sugar cane industry, particularly the native cane beetle Dermolepida albohirtum.
Explain how it is believed the cane toad, an
amphibian, is able to spread across the arid areas of
Northern Territory.
The spread across the Northern Territory is believed to follow stock routes with the toads moving from cattle dung patch to cattle dung patch following a cattle drive. This way the amphibian can stay in moist environments in the arid environment of the Northern Territory.
Explain why the cane toad is considered to be a pest
in Australia.
Cane toads are considered to be a pest in Australia due to their toxic skin secretions, lack of predators, and fast reproduction, causing ecological disruptions by harming native species and biodiversity.
The arrival of the cane toad in the Kakadu National
Park is linked to a decline in the northern quoll
population. Suggest a reason for the decrease in
number of quolls.
Quolls are a predator. If the quolls attacked the cane toads as a food source, they could be poisoned and die. Thus quoll numbers would decrease.
Assess how the experience with the cane toad impacted
on procedures for biological control in Australia.
The experience with the cane toad was highly important in
showing the need for adequate research and investigation before a species is introduced into Australia for biological control. There is not much evidence to show that the cane toad was successful in the job it was introduced to perform and since then it has become a pest itself. The experience of the cane toad shows that without thorough prior investigation an introduced species can have a major adverse impact on the environment, threaten biodiversity
and require large amounts of time, effort and money to be spent in attempts to solve the problem. From this experience a list of procedures was compiled to ensure that any future introduced biological control species would not repeat the cane toad example. Thus the cane toad experience has been highly significant in the history of biological control and has led to the development of
procedures to ensure biosecurity for Australian fauna, flora and agriculture.
In 2008 it was suggested by Rick Shine when he
won the Macfarlane Burnet Award for Excellence
that a small number of tiny cane toads should be
released in advance of the invasion front. Outline
why this proposal would slow the invasion front of
the cane toad across Australia.
Releasing smaller toads in front of the invasion front could slow the invasion front for a couple of reasons - I. Predators in the area would have a higher chance of survival if they tried to eat a small cane toad and would learn cane toads are best avoided. 2. Smaller toads would occupy areas and mate with the advancing front producing smaller offspring at the invasion front. This reduces the ‘Olympic Village’ syndrome where the ‘best’ are mating with the ‘best’ producing bigger and faster offspring each generation.
Outline how cane toad invasion has affected other
populations, e.g. red-bellied black snake populations.
Red-bellied black snakes from toad-infested areas would not eat the toads when in captivity, could more ably survive the toad poison and had smaller heads to body size and thus could not eat very large toads. Whereas red-bellied snakes from non-toad areas were likely to grab a toad when in captivity and die from the toad poison and had larger heads compared to body size and grabbed the larger and more dangerous toads.
adaptation
a feature of an organism that makes it well suited to its environment. Adaptations enhance an organism’s chances of survival.
Biodiversity
refers to the broad range of different kinds of life forms on Earth. ‘Bio’ means ‘living’; ‘diversity’ means ‘variety’.
Explain what is meant by the term biological control
‘Biological control’ refers to the use of one organism to control the numbers of another, for example as
a predator.
predict the possible consequence for the northern quoll as the cane toad population continues to increase in Australia
The northern quoll is currently listed as Critically Endangered. Further decreases in its numbers could
lead to extinction.
summarise how environmental pressures have contributed to population change in Australian native species since the introduction of the cane toad
Cane toads compete with native species for both food and habitats. Their skin contains toxic venom that can also kill native predators, as well as transfer diseases to native frogs.
list at least 3 types of adaptations that assist with thermoregulation in animals that live in hot or cold environments.
Explain how the adaptations assist the animal to survive in its environment. (Kangaroos in hot climates)
The large surface area to volume ratio of the kangaroo’s ears is a structural adaptation that allows heat to easily radiate from the surface of the ear, heat is lost from the capillaries (which come closer to the surface due to vasodilation which is a physiological adaptation) to the environment through radiation, thus reducing the internal body temperature of the kangaroo and cooling it down. During hot weather, kangaroos lick their forearms, which promotes heat loss by evaporation. This behavioural adaptation keeps them cool.
Polar bears and penguins live in similar polar environments. They have both converged on certain structural features that help them remain warm in polar conditions. List three structural features that are similar in polar bears and penguins and describe how these features help them maintain a stable body temperature.
Layer of fat surrounding the body. This insulates the body and stops heat from being lost.
Outer structural insulation layer (bear, fur, penguins, feathers) insulation reduces heat loss from the body to the environment)
Low surface area to volume ratio. Both polar bears and penguins have a rounded squat shape. (Bears more than penguins) This reduces the surface area from which to lose heat
How are selection pressures a driving factor of evolution
Selective pressures can have a significant impact on the genetic variation in a population. If a selective pressure favours a particular trait or genetic variation, individuals with that trait or variation are more likely to survive and reproduce. These favourable traits are transferred to future generations, while genes that are disadvantageous to survival and reproduction will become more rare. This change in the genetic makeup of a population is called evolution.
Hibernation
An inactive state resembling deep sleep in which certain animals living in cold climates pass the winter. In hibernation, the body temperature is lowered and breathing and heart rates slow down. Hibernation protects the animal from cold and reduces the need for food during the season when food is scarce. It is a physiological and behavioural adaptation.
Torpor
A temporary drop in body temperature and metabolic rate often accompanied by failure to eat or micturate/defecate, is an adaptation of endothermic vertebrates that enables them to survive the energetic demands of cold ambient temperature. It is a physiological adaptation.
Give an example of selection pressures
White coloured pepper moths were higher in abundance before the industrial revolution. The industrial revolution released more carbon and soot into the environment, blackening tree trunks. Due to the selective pressure in the environment, the darker moth had the more desirable trait of being dark and could therefore camouflage to avoid predators and therefore have a higher survival rate than the white peppered moth.
explain what is meant by gene flow
- the exchange of genetic material between different populations of a species, often by migration of members of the populations. In vertical gene transfer, the transfer of genetic material is from parents to offspring. It may be through sexual or asexual reproduction. In contrast, horizontal gene transfer is the movement of genetic material from a donor organism to a recipient organism that is not its offspring.
explain what is meant by genetic drift
Genetic drift is the change in frequency of an existing gene variant in the population due to random chance.
explain what is meant by natural selection
Natural selection is a process where genetic variation within a population leads to individuals having different traits in response to the change in an environment. The Galápagos finches are a classic example of natural selection. These finches have different beak sizes and shapes adapted to their food sources. During a drought, finches with larger beaks were better at cracking tough seeds, making larger beaks a desirable trait. These birds passed down the large beak trait to their offspring, resulting in large-beaked birds being more common in the finch population over time.
does a smaller or a larger population favour evolution and why
Large populations favour genetic evolution because they contain a greater diversity of genetic variations. This diversity increases the chances of individuals possessing advantageous traits that help them survive and reproduce. As these traits are passed on to the next generation, they contribute to the overall genetic makeup of the population, driving evolutionary change. Additionally, large populations are less susceptible to genetic drift (random changes in allele frequencies), which can have a stronger impact on smaller populations. This combination of genetic diversity and reduced genetic drift in larger populations promotes the accumulation of advantageous traits and adaptations, ultimately favouring evolution.
does random or assortative mating favour evolution and why
Assortative mating occurs when individuals with similar traits mate preferentially, leading to the concentration of specific traits in offspring. This can amplify certain traits, potentially enhancing a species’ adaptation to the environment.
For example, if individuals with similar beak sizes in birds tend to mate, and larger beaks are more efficient for a particular food source, assortative mating can lead to a higher occurrence of larger beak sizes in the population. This alignment between mates’ traits and advantageous traits can help populations adapt more rapidly to changing conditions.
In contrast, if mating was entirely random, the genetic diversity within the population would be maintained, but specific traits might not become as concentrated or prevalent. Assortative mating provides a mechanism for traits to become more pronounced in a population, thus favoring the evolutionary process by driving the spread of adaptive traits.
does gene flow favour evolution? why or why not
Gene flow favours evolution by introducing new genetic variation into populations. This increased genetic diversity allows for the accumulation of beneficial traits and adaptations over time. As individuals from different populations interbreed, their genetic material is exchanged, and advantageous alleles can spread more rapidly throughout the population. This process enhances the population’s ability to adapt to changing environments and promotes evolution.
do mutations favour evolution? why or why not
Consider a population of Galápagos finches with different beak sizes due to mutations. If the environment changes, such as a drought leading to larger, tougher seeds becoming more prevalent, a mutation that results in slightly larger beaks might occur in some finches. Those with the mutation can more effectively crack the tougher seeds, gaining an advantage in obtaining food. As a result, they are more likely to survive and reproduce, passing on the beneficial mutation to their offspring. Over generations, the frequency of the larger beak trait increases in the population.
Mutations introduce new traits that, when advantageous in certain environments, are favored by natural selection. By creating genetic diversity, mutations increase the likelihood of a species’ survival in changing conditions, driving evolution. They are the primary source of variation and therefore favour evolution
does natural selection favour evolution? why or why not?
Natural selection is a mechanism that drives the adaptation of species over time. Natural selection acts on heritable traits, promoting the survival and reproduction of individuals with favourable traits. This leads to the accumulation of these favourable traits in a population, resulting in evolutionary changes that have better adapted to the environment, and therefore natural selection favours evolution.
identify a factor that tends to increase genetic variation in populations
Mutation increases genetic variation by introducing new genetic variants or alleles. These changes create diverse traits within a population, providing the raw material for natural selection. Beneficial mutations can lead to advantageous traits that improve survival and reproduction. In smaller populations, mutations can have a more significant impact due to genetic drift. Over time, accumulated mutations contribute to the evolution of species and the development of distinct characteristics and an increase in genetic variation.
identify a factor that tends to decrease genetic variation in populations
Inbreeding decreases genetic variation by increasing the likelihood of offspring inheriting identical alleles from closely related parents, leading to reduced diversity and a higher prevalence of genetic disorders.
Small populations can lead to a decrease in genetic variation through a process known as genetic drift. This phenomenon occurs when chance events have a pronounced impact on the frequencies of alleles within a population. For example, consider a small population of endangered birds residing on a remote island. Owing to their limited numbers, these birds possess restricted genetic diversity. In the event of a significant storm that drastically reduces their population, the alleles carried by the surviving individuals will exert a more significant influence on the overall gene pool. Consequently, specific alleles may become dominant while others are lost, diminishing the population’s genetic variability. This reduced genetic diversity can impede the population’s capacity to adapt to environmental changes, illustrating the implications of genetic drift in small populations
Why do some animals, given the opportunity, move into new environments?
Some animals move into new environments when they experience extreme competition. An example of this is competition for resources. This occurs mainly between a group of the same species in the habitat. When the resources in the environment is smaller than the requirement of the population, one population moves out to look for more resources.
plants are unable to move. How might plants disperse to new environments?
Plants disperse to new environments through different methods. Wind dispersal involves lightweight seeds carried by air currents. Animal dispersal happens when seeds attach to animals or are consumed and then deposited in new locations. Water dispersal occurs as seeds float on water surfaces. Self-dispersal involves seed pods that burst, projecting seeds away. Explosive dispersal occurs when seed pods forcefully release seeds. Some seeds attract ants, which carry them to nests (myrmecochory). Lastly, human activities unintentionally transport seeds to new areas, aiding plant migration and expansion.
describe the amount of gene flow within a parent population prior to and during the expansion of a species range
Gene flow is the transfer of genetic material from one population to another/
explain how cycles of climate change can cause large changes in sea level (up to 200 m)
what kinds of physical barriers could isolate different parts of the same population
Physical barriers, such as mountains, bodies of water, deserts, canyons, glaciers, urban areas, vegetation zones, and geographical features, can isolate different parts of the same population. These barriers restrict movement and gene flow between populations, leading to genetic isolation. This can result in the independent evolution of distinct traits and potentially contribute to speciation processes
how mighjt emigration achieve the same effect as geographical isolation
Emigration, the movement of individuals out of a population, can achieve effects similar to geographical isolation. By physically separating a group, emigration reduces gene flow between the main population and the emigrant group. This can lead to the founder effect, genetic drift, and local adaptation in the isolated group, fostering genetic differentiation similar to what occurs with geographical barriers. Over time, the physical distance between the emigrant group and the main population can further limit gene flow and promote genetic divergence.
how might selection pressures differ for a population that becomes isolated from the parent population? Galapagos finches
