If a zebra mussel is discovered in a lake in Pennsylvania, then the ecologist would be worried because it is an invasive species. The zebra mussel is native to Ukraine and Russia, but if it has been found in Pennsylvania, than it means that it has been introduced in this area. As an invasive species, the zebra mussel can be very dangerous for the native species in the lake. The invasive species usually are more competitive for food sources than the native species, manage to reproduce quicker, bring in diseases, and the native species tend to not have defense mechanisms for them. This leads to rapid decline or even extinction in the native species, while the invasive spreads out quickly and takes over, resulting in dramatic change in the whole ecosystem.
<h3><u>Answer;</u></h3>
d. before the Neogene era.
<h3><u>Explanation;</u></h3>
- <em><u>The Silurian Period was a third period of the Paleozoic Era that occurred from 443 million to 416 million years ago. This period occurred after the Ordovician Period and was then followed by the Devonian Period.</u></em>
- Silurian period is the period that many biologically significant events took place. There was a widespread radiations of crinoids, continued priliferation and expansion of the brachiopods and also the oldest known fossils of coral reefs.
Answer:
Chloroplasts are the ’solar energy plants’ of a cell – they convert light energy into chemical energy
This chemical energy may be either ATP (light dependent) or organic compounds (light independent)
Only photosynthetic tissue possess chloroplasts (e.g. is present in leaves but not roots of plants)
Chloroplasts are thought to have once been independent prokaryotes that were internalised by eukaryotes via endosymbiosis
They have a double membrane structure (due to vesicular coating as part of the endocytotic process)
They have their own DNA (circular and naked) and ribosomes (70S)
Their metabolic processes are susceptible to certain antibiotics
The structure of the chloroplast is adapted to the function it performs:
Thylakoids – flattened discs have a small internal volume to maximise hydrogen gradient upon proton accumulation
Grana – thylakoids are arranged into stacks to increase SA:Vol ratio of the thylakoid membrane
Photosystems – pigments organised into photosystems in thylakoid membrane to maximise light absorption
Stroma – central cavity that contains appropriate enzymes and a suitable pH for the Calvin cycle to occur
Lamellae – connects and separates thylakoid stacks (grana), maximising photosynthetic efficiency
Explanation:
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The cns along with pns are bth involved in physical sensation along with the brain and spinal cord
