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3 years ago

When will natural selection occur?

Biology

2 answers:

soldier1979 [14.2K]3 years ago

6 0

Answer:

When there is limited food.

Explanation:

Vera_Pavlovna [14]3 years ago

3 0

Answer:

Explanation:

when there is limited food, then natural selection will occur

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Which organelles contain enzymes that break down old cell parts?

Lena [83]

Explanation:

A lysosome is a membrane-bound cell organelle that contains digestive enzymes. Lysosomes are involved with various cell processes. They break down excess or worn-out cell parts.

6 0

2 years ago

What is exocytosis and endocytosis? Think about what the words sound like.

german

Answer:

Endocytosis= movement of large molecules into a cell, then digestion occurs in the cell.

Exocytosis= movement of wastes from the cell.

Explanation:

Here are some examples of Endocytosis and Exocytosis:

Endocytosis= Example 1: food of Euglena, paramecium

Example 2: WBCs engulfing bacteria

Exocytosis= Example 1: wastes removal from cell

7 0

3 years ago

Read each of the sentences that describe a phase of meiosis. Place each sentence into the correct box.

Lady bird [3.3K]

Answer:

Prophase1-crossing over may occur between the non-sister chromatids

Metaphase1- Homologous chromosomes line up at the center of the cell

Anaphase and telophase 1- homologous pairs separate and move towards opposite ends of the cell, Nuclear membrane forms and cytokinesis follows.

Meiosis 2- haploid number of duplicated chromosome line up…

Sister chromatids separate and become daughter…

Four haploid daughter cells are formed….

Explanation:

Meiosis I

P-I: Chromosomes condense, nuclear membrane dissolves, homologous chromosomes form bivalents, crossing over occurs

M-I: Spindle fibres from opposing centrosomes connect to bivalents (at centromeres) and align them along the middle of the cell

A-I: Spindle fibres contract and split the bivalent, homologous chromosomes move to opposite poles of the cell

T-I: Chromosomes decondense, nuclear membrane may reform, cell divides (cytokinesis) to form two haploid daughter cells

Meiosis II

The second division separates sister chromatids (these chromatids may not be identical due to crossing over in prophase I)

P-II: Chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before)

M-II: Spindle fibres from opposing centrosomes attach to chromosomes (at centromere) and align them along the cell equator

A-II: Spindle fibres contract and separate the sister chromatids, chromatids (now called chromosomes) move to opposite poles

T-II: Chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells

The final outcome of meiosis is the production of four haploid daughter cells

6 0

3 years ago

4. Which of the following was NOT used by Wegener to support his hypothesis of continental drift?

jasenka [17]

B. Paleomagnetic data

Hope it helped

4 0

3 years ago

Which enzyme(s) involved in fatty acid synthesis utilize ATP? Select all that apply.

seropon [69]

Answer:

a. Acetyl CoA carboxylase

Explanation:

Much of the fatty acids used by the body is supplied by the diet, excessive amounts of carbohydrates and protein obtained from the diet can be converted to fatty acids and stored as triglycerides. Fatty acid synthesis occurs mainly in the liver and mammary glands, and to a lesser extent in adipose tissue and kidney, the process incorporates acetyl CoA carbons into the forming fatty acid chain using ATP and NADPH.

The acetyl portion of acetyl CoA is transported to cytosol as citrate, produced by condensation of oxaloacetate and acetyl CoA, the first reaction of the citric acid cycle, this occurs when the concentration of mitochondrial citrate is high, observed when there is a high concentration of ATP and isocitrate dehydrogenase is inhibited. The increase of citrate and ATP favors the synthesis of fatty acids, since this pathway needs both. Acetyl CoA should be converted to malonyl CoA. Carboxylation is catalyzed by acetyl CoA carboxylase and requires ATP, this reaction is the regulated step in fatty acid synthesis: it is inactivated by products, malonyl CoA and palmitoyl CoA, and activated by citrate, another regulatory mechanism is reversible phosphorylation of enzyme, which makes it inactive due to the presence of adrenaline / glucagon

5 0

3 years ago