B.4.2 Flashcards
(23 cards)
Obligate anaerobes
Some microorganisms can only respire in situations where there is not oxygen, and cannot survive in air. In fact, oxygen is toxic to them, instead of oxygen they use other compounds such as sulfate, nitrates, iron, manganese, mercury, or carbon dioxide. These are called obligate anaerobes. An example of obligate anaerobes is Clostridium difficile
Facultative anaerobes
Another microorganism is able to make ATP using oxygen if it is present, but if it is absent it can switch to fermentation, this kind of microorganism is called a facultative anaerobe. Although they can grow with both methods of respiration, they grow better with oxygen. An example of a facultative anaerobe is E.coli
Obligate aerobes
Lastly there are obligate aerobes which requiere oxygen to carry out respiration and release energy, an example of this is Mycobacterium tuberculosis.
Photosynthetic nutrition
Most autotrophs use the chemical process of photosynthesis as their means to generate their source of nutrition. This method uses light energy and converts it into chemical energy.
Carbon dioxide + water → oxygen + glucose
Specialised organelles called chloroplasts contain photosynthetic pigments that capture light energy and convert it to organic molecules which can be stored within the plant, algae, or prokaryote. It can be metabolised when needed.
- Chloroplasts can most commonly be found in leaves of plants however they can be seen in some stems.
- Algae lack the structure of plants so instead of leaves they have flattened blades called thallus and chloroplasts are found there.
- Photosynthetic prokaryotes lack membrane-bound chloroplasts and instead have infoldings in their plasma membrane on which photosynthesis takes place.
Adaptations of predators to kill prey
Physical
Many predators are carnivores and use speed and agility, sharp claws and teeth with which they can hunt and capture their prey. They also have digestive systems that are capable of breaking down the prey. Predators have very finely tuned sensory systems.
Chemical
Some predators release certain chemicals that work to either poison or paralyse their victims, these chemicals are called toxins. (venom).
Behavioural
Predators have different behavioural patterns for hunting, for example the dolphin has developed the ability to work with other dolphins to swim in circular motion and beath their tail to stir up the sea bed and create a ring of mid to trap their prey.
Adaptations of prey to resist predation
Physical
Many prey use camouflage to hide themselves and make them difficult to spot by making their coats blend into the background. They also have adapted to be quick and agile to evade capture. Some have defense mechanisms such as spines. Others might have bright colors to make predators think they contain toxic substances
Chemical
Chemicals can be released by prey that protect them from predation. These can be released into the air or water. They are usually smells that deter predators but they can also be harmful.
Behavioural
Some prey species will work together in order to look like one larger organism.
Adaptations of plants for harvesting light
For plants that life in forest ecosystems, their access to light might be limited by the forest canopy. Strategies to reach the light are needed:
- Some plants are epiphytes; plants that grow on the surface of other plants using them for support, they use the moisture from the plant as their source of water, rather than gaining it from the soil.
- In the shrub-layer of the forest plants are shade-tolerant and have leaf modifications having a larger surface area with thin and broad leaves to allow the maximum amount of sunlight to hit them.
Fundamental niches
- All the conditions an organism could theoretically survive in
- Bigger
Realised niches
- The places that the organisms actually live in
- Smaller due to competition
- Within the same species it is intraspecific
- Between species it is interspecific
Realized niches are formed when the species within a fundamental niche has to deal with the pressure of co-existing with the other species in the environment, forcing it to live in a smaller niche.
Experiment for type of cell respiration
An experiment to tell what type of respiration a microorganism does is by growing a simple experiment growing bacteria in a special culture medium containing thioglycolate. This allows for the movement of bacteria, using a low amount of sugar and removing the oxygen from the media. The top of the tube is exposed to air and overtime oxygen will diffuse into the media and allow more oxygen at the top of the tube. Obligate aerobes will be on the top of the medium as that is where the highest concentration of oxygen is. Obligate anaerobes will be found at the bottom of the medium because that part is devoid of oxygen and lastly the facultative anaerobes will be found anywhere in the medium.
Types of species
- Specialist species
- Adapted to narrow habitats, limited food resources, or other specific environmental conditions. They are often the most vulnerable when conditions change.
- Generalist species
- Species adapted to a wide variety of habitats, food resources, and environmental conditions. They are more likely to survive when conditions change.
Ecological niche
- An ecological niche refers to not only where an organism lives but also on what it does.
- The distribution of species is determined by interactions from the environment (both abiotic and biotic).
- Biotic → competition with other species for resources, disease, predators, and parasites
- Abiotic → Temperature, pH, wind, precipitation, amount of sunlight, water availability, and soil
These factors work together to create a specific ecosystem in which only certain organisms can survive.
Not only does the environment impact the distribution of species, but certain organisms can elicit a huge impact on their environment.
Holozoic nutrition
Heterotrophic organisms take in their food as their source of nutrition. Holozoic nutrition refers to organisms that take in solid or liquid food internally. Most animals are holozoic, but protozoa and Amoebas also use this method. After the food is brought inside the organism, it will be digested into organic building blocks. These are then used to build up new materials for the growth and development of the organism.
Mixotrophic nutrition
Mixotrophic organisms are able to use a combination of methods of generating their nutrition and are neither fully autotrophic or heterotrophic. Mixotrophic microbes are able to photosynthesise like plants and therefore take in CO2, but they can take in nutrition like an animal, as they respire they then release CO2.
Mixotrophs can be divided into 2 main categories:
- Facultative mixotrophs, they can switch between autotrophic and heterotrophic modes of nutrition depending on their conditions within the environment.
- Obligate mixotrophs must use both modes.
Saprotrophic nutrition
Saprotrophic nutrition is a method by which the organism secretes digestive enzymes that are able to break down the dead organic material, including the tough components of dead plants such as cellulose, hemicellulose, and pectin. The enzymes break up the material into simpler molecules which are then absorbed by the organism. Most fungi are examples of this nutrition
Without these organisms forest floors would be piled high with organic litter.
Adaptations of animals for herbivory
Herbivores have specialised ways to be able to take in plant material and be able to break it down.
- Some insects have evolved to have strong mandibles to cut, tear, crush, and chew their food.
- Other insects feed off the fluids internal to the plant and use a unique straw-like device called a stylet to access it.
In herbivorous mammals, their front incisors are long and flat and work like scissors to cut the plant materials. The black molars are large, flat surfaces where the plant material can get smashed in a sideways, griding movement to increase the surface area for digestive enzymes to break it down.
Due to constant griding, herbivores can wear their teeth down and therefore have constant teeth growth. the space between the incisors and molars is called a diastema, and this area allows the tongue to move the food from the front of the mouth to the molars for grinding.
Herbivores need to be aware of predators around them so they have eyes that are far apart on either sides of their head to increase their visual field so they can respond more quickly to danger.
Adaptations of plants to avoid herbivority
Some plants make toxic secondary compounds. Some animals have responded to this by evolving special enzymes to digest the toxic compounds and to further respond plants evolved non-toxic chemicals that only become toxic after ingestion by the animal. This back and forth is called “animal plant warfare”. (Poison)
Some medicines have been derived from the secondary compounds.
Other plants adopt a way of hiding from predators like camouflage or size or mechanical deterrents such as thorns or tiny hairs that irritate the skin
Coexistance with other species
It is not possible for two species to occupy the same niche for a long period of time, and one will outcompete the other. This is called competitive exclusion principle/Gause’s law.
Niche partitioning
Competition will often cause there to be adaptations in order for both species both survive. A concept is called niche partitioning showed how natural selection permits competing species to occupy close areas or niches.
There are 2 types of niche partitioning
- Spatial partitioning
The division of habitat among different species, where each species occupies a distinct area or microhabitat withing the same larger environment. This reduces competition for the same resources in the same place.
- Temporal partitioning
A type of niche partitioning where species coexist utilizing the same resources but at different times, such as different parts of the day or year. This reduces competition for the same resources at the same time
Archaea diversity nutrition
It is thought that archaea are the most ancient organisms on the planet.
Members of the archaea are those that have an ability to survive in extreme environments. These archaeans have evolved the enzymes needed to allow them to survive these extraordinary conditions. The method in which they derive their energy is very diverse and they can use a wide variety of sources.
- Some are able to use oxidation of inorganic chemicals such as sulfur, hydrogen sulfide, iron, or ammonia for their metabolism and are called chemoautotrophs.
- Others photoautotrophs and use light as their source of energy
- Others are heterotrophs and need to gain their energy from organic compounds. Some of these use carbon dioxide or other organic compounds to produce methane gas through methanogenesis
Archaic megadont hominis dentition
Paranthropus robustus existed about 2.2 to 1.5 million years ago in South Africa. They had large teeth with thick enamels and chewed at the back of their jaw. They had large chewing muscles which resulted in them having a wide face. A large bone called the sagittal crest is a line of bone that runs along the midline of the skull towards the nose. The presence of this shows that this hominin had strong jaw muscles, therefore they have the ability to grind through tough fibrous foods. They were believed to be herbivores.
Pre-modern homo dentition
Homo floresiensis was a species present 100,000 to 50,000 years ago. They had small brains but large teeth for their skull size. It is believed that they were omnivores and that their diet included both plant and uncooked meat. The evidence for this is the markings on their teeth that show wear that coincides with eating tough fibrous diet that required a lot of chewing. Failed to adapt therefore they died before Homo sapiens could find them.
The modern Homo sapiens were found from 196,000 years ago to the present day, and all humans on the planet are of this genus and species. Although they likely evolved in Africa and are now found throughout the entire planet. They gathered food and hunted, and were able to develop methods to help them survive with changing conditions. The jaws are also less heavily developed, with smaller teeth.
Teeth in different diets
Carnivores have:
- Large pointed canines
- Small incisors
- Pointed molars and premolars
- Strong jaws for predators of large prey
Omnivores:
- Medium sized blunt canines
- Incisors are larger and sharper
- Cusps (lumps) on molars
- No evidence of jaw involvement
Herbivores:
- Small diamond shaped canines
- Flattened incisors
- Flat molars from grinding
- Strong jaw muscles for chewing hard foods.
