Answer:
True
Explanation:
The embryonic development of fertilized egg includes cleavage, blastulation, implantation, gastrulation and organogenesis.
Cleavage division divides the zygote into blastomeres. First cleavage division result in two blastomeres, second cleavage division results in a transient three cell stage. Third cleavage division forms 8 blastomere. These result in the formation of a sold ball of cells called morula. Morula is 16 cell stage and it descends towards the uterus in 4-6 days. As the morula enters the uterus, it gets a rich supply of nutrients. Trophoblast cells are formed which secrete a fluid into the interior creating a cavity called blastocoel. The inner cell mass now comes to lie on one side as embryonal knob. With the formation of blastocoel, morula is converted into blastula which is called blastocyst in mammals.
The four types of global winds are:
1. Jet streams
2. Polar easterlies
3. Westerlies
4. Trade winds
C. Sharks eat smaller fish, seals, and sea lions.
Carnivores only eat meat.
Answer:
Without elephants, some of the grasslands in Africa would eventually become thickets or forests because elephants weed out trees and shrubs. Even though elephants make up a small percentage of the animals living on the grassland, the grassland would eventually cease to exist without them. In this community, elephants are <u>keystone species</u>.
Elephants are often called “keystone species” because of their unique role in providing vital services to an ecosystem in relation to their abundance.
Explanation:
Elephants play a very important role in maintaining the biodiversity of the ecosystems in which they live. During the dry season, elephants use their tusks to dig for water. This not only allows the elephants to survive in dry environments and when droughts strike, but also provides water for other animals that share harsh habitats.
Elephants eat some trees and create gaps in the vegetation. These allow new plants to grow and create pathways for other smaller animals to use. They are also agent of seed dispersal of trees and in fact some species of trees rely entirely upon elephants for seed dispersal.
Elephants feed on tree sprouts and shrubs in savannahs. They help keep the plains open and able to support the plains game that inhabit these ecosystems.
Elephants also leave a dung that is full of seeds from the many plants they eat. When this dung is deposited, the seeds are sown and grow into new grasses, bushes and trees, thereby boosting the proliferation organisms in the savannah ecosystem.
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