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Specific Learning Outcomes
Specific Learning Outcomes
By the end of this unit you should be able to:
define a habitat as the place and conditions in which an organism lives
recognize the significant features of a particular habitat that would favour the survival of some types of organism and not of others e.g. cold temperature and snowfall in an alpine habitat
classify factors which can influence the survival as physical (abiotic) and biological (biotic)
describe the special features which help an organism to survive as adaptations
classify adaptations as structural, functional or behavioural
recognise structural adaptations as those related to an organisms physical shape or the properties of the physical structure, and be able to relate those adaptations to the way they help the organism survive
define functional adaptations as those features which relate to the way the organism's physiology (the processes in its body), such as the sugar-rich sap of a cabbage tree or the fast hearbeat of a fantail
recognise behavioural adaptations as the ways organisms respond to features or changes in their environment, such as a plants's growth towards light or a bird'staking flight when a threat is sighted
be able to identify the adaptations of an example organism and specify which type of adaptation it is
work out how the particular adaptions of an organism might enable it to better carry out one or more of the seven life processes (MRSGREN)
explain that the survival of a species requires not only survival of individual organisms, but successful reproduction at a rate sufficient to maintain or increase the size of the population
give examples of the way that adaptations interact with both biotic and abiotic factors to help the survival of a species
recall that a species is a group of organisms capable of interbreeding, and that a population is a breeding group
recall that the individual members of a species will be slightly different from each other; apply the term variation to these differences and relate them to genes and alleles
recognise that because of variation some members of a population are likely to be better suited to survival and breeding than others in particular conditions, and that as long as such characteristics can be inherited they will become more common in the next generation.
apply the term natural selection to this selection of traits important to a species' survival
explain that this can result in a gradual change in the traits of a population over time or space in circumstances where conditions can vary
apply the term evolution to the gradual change over time
Habitat
Habitat
A habitat is the place where an organism lives. Examples of habitats include a sandy desert, the rocky shore, tidal mudflats, forest floor, forest canopy and so on. Habitats can be fairly specific, and habitats have particular conditions in which the living organisms found in it must survive.
Some organisms can live in a wide range of habitats, e.g. rats; others have very specific needs and are only found in particular places e.g. limpets live in the tidal zone of the rocky shore - they can't live on mud or sand, or above high tide or in very deep water.
The organisms living in a habitat are influenced by factors such as temperature, light levels, availability of water, predators, disease and parasites. These factors group into two categories:
Biotic or biological factors are those that relate to other organisms, such as predators, food supply, disease, competition, mating opportunities and so on
Abiotic or physical factors are those related to physical things in the environment, such as temperature, light levels, soil nutrients, salinity and so on.
Habitats Worksheet - Tundra & Desert - PDF
Habitats Worksheet - Seaweed - PDF
Example answers in white font. There are a range of possible answers to these questions. This work overlaps with some of the work in the Balancing Acts unit.
Checkpoint
Checkpoint
A habitat is the place where an organism lives.
The factors in a habitat determine what kind of organisms can live there.
These factors are split into living (biotic) and nonliving (abiotic) factors.
Test your knowledge of habitats using this short quiz!
Extreme Environments
Extreme Environments
Life appears to adapt to any possible opportunity. An habitat such as a coral reef or a rain forest will have a huge variety of organisms inhabiting it.
Some environmental conditions are challenging for life processes and a much smaller range of organisms are capable of enduring them. Examples of such environments:
deep rock
hot springs
underwater hydrothermal vents
very salty (hypersaline) environments
extreme cold (polar and alpine)
extreme aridity (desert)
unusual pH (e.g. very acid conditions in bogs)
Epiphyte on kauri tree
All organisms have special features to help them survive. However, in these environments organisms are likely to require their life processes to operate considerably outside biological norms. Features that help an organism to survive are called adaptations and we will look at them in the next section.
Note that there can be a range of habitats (or at least of environmental conditions) in a particular community. For example, the trunk of a kauri tree might not seem like a good 'home' for a plant. There are few nutrients, it is fairly easy to be dislodged and so on. However, one biotic factor tends to ensure plants evolve to exploit this "opportunity": competition. This is an environment in which only certain specialised plants can live, so the plant doesn't have to compete for space with lots of other species. It may have other advantages, such as better light levels and relative freedom from predation.
One reason for the huge variety of different living organisms on Earth is adaptation to better take advantage of biotic and abiotic factors in a habitat, and potentially enter a habitat in which no other organism can survive.
Adaptations
Adaptations
Adaptations are special features that help an organism to survive. They are particular to the environment in which the organism lives. For example, think about a cactus growing in the desert:
The environment
Hot in daytime, cold at night (could be below zero)
Water is scarce much of the time, and often only available for a short time
Animals are likely to want to steal the plant’s water
Therefore:
Cacti use a special type of photosynthesis where they don’t have to open their stomata (the gas exchange holes in their leaves) in the heat of the day.
They can store a lot of water in their stems, and rapidly absorb water through their shallow roots after a rainstorm
They are covered in spines to stop animals stealing their water
They are thick and rounded to avoid frost damage
These adaptations are particular to the environment where a cactus lives; for example, they would be little use on the floor of a rainforest, and the reduced leaf area that cacti have available for photosynthesis would be a disadvantage in the low light of the forest. Adaptations can be grouped into three categories:
Structural adaptations are those related to the organisms structure, In the case of the cacti above, the spines and the rounded shape are both structural adaptations .
Functional adaptations are those that relate to the organism’s overall physiology. This means the way that its body works. In the case of the cacti above, functional adaptations include a changed photosynthetic cycle so they don't have to have their stomata open in the heat of the day. Another functional adaptation is the way they store water. There is some overlap between functional and structural adaptations, e.g. the cacti's roots' ability to absorb water.
Behavioural/response adaptations are those that relate to an organism's behaviour or responses. For the cacti, this would include opening their stomata for gas exchange at night.
Adaptations are a response to the environmental factors, biotic and abiotic. If conditions change, then organisms whose adaptations are better suited to the new conditions will survive better and be more likely to breed. Therefore they will pass these traits on to their offspring which will also survive better in the same conditions and be more likely to breed. Overtime the organisms that are adapted better to the conditions are specialised for this niche and may eventually become a new species from the original. This process is called evolution.
Example: Grizzly bears have an occasional mutation which gives them white fur. During the ice ages, grizzlies with white fur had better camouflage in the snow, and were more successful hunters in the parts of North America with permanent snow.
The proportion of grizzlies with this mutation grew in these areas. Meanwhile, the grizzlies back in the south where there was only snow at winter continued to have only the occasional white mutant.
Eventually, the white grizzlies formed a separate population. Because their main prey were seals and other marine organisms, this population also accumulated traits to make them better swimmers and give them greater protection from the cold. They also have abnormally large feet compared to grizzlys allowing them to walk on the snow and not sick in (like snow shoes). We now call the white grizzlies polar bears and regard them not just as a separate population but as a separate species.
Case Study Takahe|Pukeko - PDF
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